Answer:
b :)
Explanation:
an exothermic reaction is when heat/light is produced. heart is produced from this reaction so it is exothermic
The correct answer is option c. The reaction between salt and water is endothermic.
How are salt and water endothermic?Chemical reaction
Salt is a hygroscopic material that attracts water and heat from its surroundings. This is why leather shoes are "dry" and wrinkled when covered with salt. This type of reaction is known as an endothermic reaction, which is a chemical reaction that absorbs heat.
Endothermic reaction: A chemical reaction that absorbs heat is called an endothermic reaction. The temperature will drop. For example, (i) heating nitrogen and oxygen together to a temperature of about 3000 ° C produces nitrogen oxide gas. N2 + O2 + heat → 2NO (g)
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Interpret the following equation for a chemical reaction using the coefficients given: CO(g) Cl2(g) COCl2(g) On the particulate level: _________ of CO(g) reacts with _________ of Cl2(g) to form _________ of COCl2(g). On the molar level: _________ of CO(g) reacts with _________ of Cl2(g) to form _________ of COCl2(g).
Answer:
On the particulate level: 6.02 * 10²³ particles of CO(g) reacts with 6.02 * 10²³ particles of Cl₂(g) to form 6.02 * 10²³ particles of COCl2(g).
On the molar level: 1 mole of CO(g) reacts with 1 mole of Cl2(g) to form 1 mole of COCl₂(g).
Explanation:
The particulate level refers to the microscopic or atomic level of substances. It also involves the ions, protons, neutrons and molecules present in substances.
The molar level refers to the quantitative measure of substances in terms of the mole, where a mole represents the amount of substances containing the Avogadro number of particles which is equal to 6.02 * 10³ particles.
Equation of the reaction: CO(g) + Cl₂(g) ----> COCl₂(g)
From the equation above, I mole of CO gas reacts with 1 mole of Cl₂ gas to produce 1 mole of COCl₂ gas.
Since 1 mole of a substance contains 6.02 * 10²³ particles, on a particulate level, 6.02 * 10²³ particles of CO gas reacts with 6.02 * 10²³ particles of Cl₂ gas to produce 6.02 * 10²³ particles of COCl₂ gas.
Which of the following errors could cause your percent yield to be falsely high, or even over 100%?
Select ALL that apply.
A.) Heating the sample too vigorously.
B.) Handling the crucible directly with your hands.
C.) Failing to completely decompose the sodium bicarbonate sample.
D.) Taking the mass of the empty crucible without the lid, but including the lid in all other mass measurements.
E.) Taking the mass of all samples with the lid included.
Answer:
B.Handling the crucible directly with your hands.
D.Taking the mass of the empty crucible without the lid, but including the lid in all other mass measurements.
E.Taking the mass of all samples with the lid included.
Explanation:
When observed critically , the measures associated with the errors which could cause your percent yield to be falsely high, or even over 100% are those which increase the weight of the substance with the individual neglecting.
Handling the crucible directly with your hands,Taking the mass of the empty crucible without the lid, but including the lid in all other mass measurements and taking the mass of all samples with the lid included will all increase the weight of the substance. Instead the substance should be placed alone without any form of support or contamination.
A chemistry student weighs out of an unknown solid compound and adds it to of distilled water at . After minutes of stirring, only some of the has dissolved. The student drains off the solution, then washes, dries and weighs the that did not dissolve. It weighs 0.570 kg.
Required:
a. Using the information above, can you calculate the solubility of X?
b. If so, calculate it. Remember to use the correct significant digits and units. .
Complete Question
A chemistry student weighs out 0.950 kg of an unknown solid compound and adds it to 2.00 L of distilled water at . After minutes of stirring, only some of the has dissolved. The student drains off the solution, then washes, dries and weighs the that did not dissolve. It weighs 0.570 kg.
Required:
a. Using the information above, can you calculate the solubility of X?
b. If so, calculate it. Remember to use the correct significant digits and units. .
Answer:
a
Yes the solubility of X can be calculated this is because the solubility of a substance dissolved in a solution is the amount of that substance that is needed to saturate 1 unit volume of the solvent solution at that given temperature.
And from our question we see that substance X saturated the solvent and there is still remained undissolved substance X
b
The solubility of X is [tex]S = 190 g /L[/tex]
Explanation:
From the question we are told that
The initial mass of the unknown solid is [tex]m_i =0. 950 \ kg[/tex]
The mass of the undissolved substance is [tex]m_u = 0.570 \ kg[/tex]
The volume of the solution is [tex]V =2.00\ L[/tex]
Yes the solubility of X can be calculated this is because the solubility of a substance dissolved in a solution is the amount of that substance that is needed to saturate 1 unit volume of the solvent solution at that given temperature.
And from our question we see that substance X saturated the solvent and there is still remained undissolved substance X
The mass of the substance that dissolved ([tex]m_d[/tex] ) is mathematically represented as
[tex]m_d = m_i - m_u[/tex]
[tex]m_d = 0.95 - 0.570[/tex]
[tex]m_d = 0.38 \ kg = 0.38 *1000 = 380 g[/tex]
The solubility of this substance (X) is mathematically represented as
[tex]S = \frac{m_d}{V}[/tex]
substituting values
[tex]S = \frac{ 380}{2}[/tex]
[tex]S = 190 g /L[/tex]
Alkyl derivatives of mercury are highly toxic and can cause mercury poisoning in humans. Dimethylmercury is one of the strongest known neurotoxins. Although it is said to have a slightly sweet smell, inhaling enough to discern this would be hazardous.
Give the empirical formula of dimethylmercury.
Answer:
The empirical formula of dimethylmercury is C2H6Hg
Explanation:
Dimethylmercury, as it says in the name, presents not only the mercury metal in its structure (Hg) but also two radical groups called methyl, which is why its name begins with the prefix DI, referring to the fact that there are two methyl.
Catalysts are substances that increase the rate of reaction but can be recovered unchanged at the end of the reaction. Catalysts can be classified as either homogeneous (same state as reactants) or heterogeneous (different state than reactants).
Platinum is used to catalyze the hydrogenation of ethylene:
H2(g)+CH2CH2(g)−⟶Pt(s)CH3CH3(g)
Chlorofluorocarbons (CFCs) catalyze the conversion of ozone (O3) to oxygen gas (O2):
2O3(g)−⟶CFC(g)3O2(g)
Magnesium catalyzes the disproportionation of hydrogen peroxide to produce water and oxygen:
2H2O2(aq)−⟶Mg(s)2H2O(l)+O2(g)
What type of catalysts are platinum, CFCs, and magnesium under these conditions?
Answer:
- Platinum acts as a heterogeneous catalyst in the hydrogenation of ethylene.
- CFCs act as homogeneous catalysts in the conversion of ozone to oxygen gas.
- Magnesium acts as a heterogeneous catalyst in the disproportionantion of hydrogen peroxide.
Explanation:
Hello,
For the given reactions, considering the definition of homogeneous and heterogeneous catalyst, we can identify that is each catalyst behave as follows:
- Platinum acts as a heterogeneous catalyst in the hydrogenation of ethylene as all the reactants are gaseous but it remains solid.
- CFCs act as homogeneous catalysts in the conversion of ozone to oxygen gas as it remains gaseous as well as both ozone and oxygen.
- Magnesium acts as a heterogeneous catalyst in the disproportionantion of hydrogen peroxide as it is solid whereas the other species are aqueous, liquid and gaseous
Best regards.
Given the equation 2KCIO3(s)=2KCI(s) + 3O2(g). A 3.00-g sample of KCIO3 is decomposed and the oxygen at 24 degrees C and 0.982 atm is collected. What volume of oxygen gas will be collected assuming 100% yield?
Answer:
0.912 L or 912 mL
Explanation:
M(KClO3) = 122.55 g/mol
3.00 g KClO3 * 1 mol/122.55 g = 3.00/122.55 mol =0.02449 mol
2KCIO3(s)=2KCI(s) + 3O2(g)
from reaction 2 mol 3 mol
given 0.02449 mol x
x = 0.02449*3/2 =0.03673 mol O2
T = 24 + 273.15 = 297.15 K
PV = nRT
V= nRT/P = (0.03673 mol*0.082057 L*atm/K*mol*297.15 K)/0.982 atm =
= 0.912 L or 912 mL
A 11.0 mLmL sample of 0.30 MHBrMHBr solution is titrated with 0.16 MNaOHMNaOH. Part A What volume of NaOHNaOH is required to reach the equivalence point? Express the volume to two significant figures and include the appropriate units. nothingnothing
Answer:
21 mL of NaOH is required.
Explanation:
Balanced reaction: [tex]HBr+NaOH\rightarrow NaBr+H_{2}O[/tex]
Number of moles of HBr in 11.0 mL of 0.30 M HBr solution
= [tex](\frac{0.30}{1000}\times 11.0)[/tex] moles = 0.0033 moles
Let's say V mL of 0.16 M NaOH solution is required to reach equivalence point.
So, number of moles of NaOH in V mL of 0.16 M NaOH solution
= [tex](\frac{0.16}{1000}\times V)[/tex] moles = 0.00016V moles
According to balanced equation-
1 mol of HBr is neutralized by 1 mol of NaOH
So, 0.0033 moles of HBr are neutralized by 0.0033 moles of NaOH
Hence, [tex]0.00016V=0.0033[/tex]
[tex]\Rightarrow V=\frac{0.0033}{0.00016}=21[/tex]
So, 21 mL of NaOH is required.
Which of the following is evidence for a physical change? A) burning B) fizzing C) evaporating D) rusting
Answer:c
Explanation: rusting, burning and fuzzing are all examples of chemical reactions/changes.
Which of the following is named using the unmodified element name and adding the word "ion"? Select the correct answer below:
a. simple cations (monatomic cations of elements of only one possible charge)
b. simple anions (monatomic anions of elements of only one possible charge)
c. simple protons
d. simple neutrons
Answer:
simple cations (monatomic cations of elements of only one possible charge)
Explanation:
Simple cations (monatomic cations of elements of only one possible charge) are named using the unmodified element name and adding the word "ion"
For example, the Na+ is named the sodium ion.
An atom or molecule with a net electric charge as a result of the loss or gain of one or more electrons is known as an ion.
A gas has a volume of 6.6 L at a temperature of 40 C. What is the volume of
the gas if the temperature changes to 15 C?
Answer:
6.07 L
Explanation:
It appears that the reading has been made at constant pressure .
At constant pressure , the gas law formula is
V/T = constant V is volume and T is temperature of the gas.
V₁ / T₁ = V₂ / T₂
V₁ = 6.6 L ,
T₁ = 40°C
= 273 + 40
= 313 K
T₂ = 15+ 273
= 288K
V₂ = ?
Putting the values in the formula above
6.6 / 313 = V₂ / 288
V₂ = 6.07 L.
most reactions give off energy in the form of heat and are called what
Answer:
Exothermic reaction.
Explanation:
One of the reagents below gives predominantly 1,2 addition (direct addition) while the other gives predominantly 1,4 addition (conjugate addition). a) Which major organic product is the result of 1,2 addition? ---Select--- b) Draw the skeletal structure of major organic product A
Complete Question
The complete question is shown on the first uploaded image
Answer:
a
The correct option is reagent B
b
The skeletal structure of major organic product A is shown on the third uploaded image
Explanation:
The mechanism of the reaction for A and B are shown on the second the second reaction and looking at this we can see that the reagent that predominately gives 1,2 addition is reagent B
A thermometer is placed in water in order to measure the water’s temperature. What would cause the liquid in the thermometer to rise? The molecules in the water move closer together. The molecules in the thermometer’s liquid spread apart. The kinetic energy of the water molecules decreases. The kinetic energy of the thermometer’s liquid molecules decreases.
Answer:
The molecules in the thermometer’s liquid spread apart
Explanation:
The molecules in the thermometer’s liquid spread apart.
What is thermometer?A thermometer is a device that measures temperature or a temperature gradient.
What causes the liquid in the thermometer to rise?The liquid (water) in thermometer exhibits convex meniscus, as a result of this meniscus, the water molecules in the thermometer will spread apart when temperature is measured.
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When nitrogen dioxide (NO2) gas from car exhaust combines with water in the air, it forms nitrogen oxide and nitric acid (HNO3), which causes acid rain, and nitrogen oxide. Balanced eqjation:
(NO); 3NO2(g) + H20(l) --> 2HNO3(aq) + NO(g).
A) How many molecules of NO2 are needed to react with 0.250 mol of H2O?
B) How many grams of HNO3 are produced when 60.0 g of NO2 completly reacts?
C) How many grams of HNO3 can be produced if 225 g of NO2 is mixed with 55.2 g of H2O?
Answer:
A. 0.75 moles NO2 are required
B. 82.2 gnof HNO3 are produced
C. 205.3 g of HNO3 are produced
Explanation:
Check attachment below for explanation and calculations
What is the conjugate acid in the following equation hbr + H2O yields h30 positive + BR negative
Answer:
HBr + H2O = H3O+ + Br-
So our conjugate acid is the H3O+ to H2O
Explanation:
A conjugate acid of a base results when the base accepts a proton.
Consider ammonia reacting with water to form an equilibrium with ammonium ions and hydroxide ions:
NH3 (aq) + H2O (l) ⇌ NH4+ (aq) + OH- (aq)
Ammonium, NH4+, acts as a conjugate acid to ammonia, NH3.
Why are there different theories about the effects of global warming?
At that volume is measured to be 755 mm of Hg. If the lungs are compressed to a newA healthy male adult has a lung capacity around 6.00 liters. The pressure in the lungs volume of 3.81 liters, what would be the new pressure in the lungs? What would happen to the air in the lungs?
Answer:
1188.976 mmHg
Explanation:
Initial pressure P1= 755 mmHg
Initial volume V1 = 6.00 litres
Final volume V2 = 3.81 litres
Final pressure P2= the unknown
Now applying Boyle's Law,we have;
P1V1 = P2V2
Since P2 is the unknown then it has to be made the subject of the formula.
P2=P1V1/ V2
P2= 755 × 6.00/ 3.81
P2= 1188.976 mmHg
Therefore, the new pressure is; 1188.976 mmHg
Give the IUPAC name for the following compound: Multiple Choice (1R,3R)-1-ethyl-3-methylcyclohexane (1S,3S)-1-ethyl-3-methylcyclohexane (1R,3S)-1-ethyl-3-methylcyclohexane (1S,3R)-1-ethyl-3-methylcyclohexane
Answer:
(1R,3R)-1-ethyl-3-methylcyclohexane.
Explanation:
NOTE: The question is not complete since we do not have the diagram to the chemical structure in the question. Kindly check the attached picture for the diagram of the chemical structure.
So, in order to name Enantiomers or chemical structure through the use of the R,S system requires series of rules and regulations to follow for the proper naming.
There is an ethyl attached to the compound as the first substituents and methyl at the third which are the secondary prefix.
=> The longest chain is 6, thus the compound has hexane as the root compound.
=> It is (1R,3R) because when we draw from the highest substituents to the lower substituents, this is done in a clockwise direction.
Acetic acid and ethanol react to form ethyl acetate and water.If 94.0 mmol of C2H5CO2CH3 are removed from a flask containing a mixture of HCH3CO2, C2H5OH, C2H5CO2CH3 and H2O at equilibrium, then following questions are to be answered. 1. What is the rate of the reverse reaction before any C2H5CO2CH3 has been removed from the flask?2. What is the rate of the reverse reaction just after the C2H5CO2CH3 has been removed from the flask?3. What is the rate of the reverse reaction when the system has again achieved equilibrium?4. How much less C2H5CO2CH3 is in the flask when the system has again reached equilibrium?
Answer:
Explanation:
The equation for the react between Acetic acid and ethanol to form ethyl acetate and water is :
[tex]HCH_3CO_2_{(aq)}+C_2H_5OH_{(aq)} \to C_2H_5CO_2CH_3_{(aq)} + H_2O_{(l)}[/tex]
Imagine if 94.0 mmol of [tex]C_2H_5CO_2CH_3[/tex] are removed from a flask; Then:
We are to answer the following questions:
1. What is the rate of the reverse reaction before any [tex]C_2H_5CO_2CH_3[/tex] has been removed from the flask?
The reaction above is called an esterification reaction;
So the rate of reverse reaction before any [tex]C_2H_5CO_2CH_3[/tex] is removed is greater than zero and equal to forward reaction rate.
2. What is the rate of the reverse reaction just after the [tex]C_2H_5CO_2CH_3[/tex] has been removed from the flask?
Just after the [tex]C_2H_5CO_2CH_3[/tex] has been removed from the flask, the rate of the reverse reaction is greater than zero but less than forward reaction rate.
3. What is the rate of the reverse reaction when the system has again achieved equilibrium?
When the system has again achieved equilibrium, the rate of the reverse reaction is greater than zero and equal to forward reaction rate because we it has achieved the equilibrium, hence, the reaction tends to proceed in the forward direction.
4. How much less [tex]C_2H_5CO_2CH_3[/tex] is in the flask when the system has again reached equilibrium?
The [tex]C_2H_5CO_2CH_3[/tex] in the flask when the system has again reached equilibrium is lesser by 94.0 mmol as given right from the question
please help!!!! Chem question
Answer : The net ionic equation will be,
[tex]Ba^{2+}(aq)+SO_4^{2-}(aq)\rightarrow BaSO_4(s)[/tex]
Explanation :
In the net ionic equations, we are not include the spectator ions in the equations.
Spectator ions : The ions present on reactant and product side which do not participate in a reactions. The same ions present on both the sides.
The given balanced ionic equation will be,
[tex]Ba(OH)_2(aq)+H_2SO_4(aq)\rightarrow 2H_2O(aq)+BaSO_4(s)[/tex]
The ionic equation in separated aqueous solution will be,
[tex]Ba^{2+}(aq)+2OH^-(aq)+2H^{+}(aq)+SO_4^{2-}(aq)\rightarrow BaSO_4(s)+2H^+(aq)+2OH^{-}(aq)[/tex]
In this equation, [tex]H^+\text{ and }OH^-[/tex] are the spectator ions.
By removing the spectator ions from the balanced ionic equation, we get the net ionic equation.
The net ionic equation will be,
[tex]Ba^{2+}(aq)+SO_4^{2-}(aq)\rightarrow BaSO_4(s)[/tex]
Rubidium is ______ potassium in the periodic table. lodine is ______ bromine in the periodic table. Therefore, the rubidium ion is __________ than the potassium ion, and the iodine ion is___________ than the bromide ion. The _______ the distance between the rubidium ion and the iodide ion is the potassium ion and the bromide ion. Therefore, the energy associated with the interaction between rubidium and iodide is________ atomic radius means that than that between , and the lattice energy of potassium bromide is ________ more exothermidc.
Answer:
The given blanks can be filled with below, below, larger, larger, larger, larger and smaller.
Explanation:
In the periodic table, rubidium comes below the potassium, and iodine comes below bromine. Therefore, it can be said that the ion of rubidium is larger in comparison to potassium ion, and similarly the ion of iodine is larger in comparison to the ion of bromine.
When the atomic radius is larger it signifies that the distance in between the ion of iodine and the ion of rubidium is larger in comparison to that between the ion of potassium and the ion of bromine. Thus, smaller energy is associated with the interaction between iodine and rubidium, and potassium bromide's lattice energy is more exothermic.
One proposed mechanism of the reaction of HBr with O2 is given here. HBr + O2 → HOOBr (slow) HOOBr + HBr → 2HOBr (fast) HOBr + HBr → H2O + Br2 (fast) What is the equation for the overall reaction?
Answer:
4 HBr + O2 → + 2H2O + 2Br2
Explanation:
Based on the following reaction mechanism:
HBr + O2 → HOOBr (slow)
HOOBr + HBr → 2HOBr (fast)
HOBr + HBr → H2O + Br2 (fast)
The equation for the overall reaction is the sum of the three reactions in which intermediaries of reaction (HOBr and HOOBr are canceled). That is 1 + 2 + 2*(3):
HBr + O2 + HOOBr + HBr + 2HOBr + 2HBr → HOOBr + 2HOBr + 2H2O + 2Br2
4 HBr + O2 → + 2H2O + 2Br2Beeing this reaction the equation of the overall reaction.
The realization that guanine and thymine base pair to cysteine and adenine, respectively, through their keto-like tautomeric forms has ultimately led to which types of technologies seen in popular TV shows like CSI and Law and Order?
a. DNA sequencing and profiling
b. Flexible display monitors
c. Smart phones
d. Police cars
Answer:
The correct answer to the following question will be Option A (DNA sequencing and profiling).
Explanation:
It is indeed a procedure through which a specific DNA sequence named as the profile is chosen to take from either a sample or perhaps a survey. For humans, much more of the DNA sequence will be the same, although only different regions differ in sequencing, such locations are considered polymorphic. The disparity between individuals regardless of such a particular process is named as polymorphisms, and then this method is being used in the detection of murders, parental conflicts, etc.The other three situations aren't connected to the situation in question. That option 1 seems to be the right answer.
Pick the odd one out?
Ethanol
Hexane
Oil
Carbon tetrachloride
Answer: Ethanol is the odd one out.
Explanation:
A polar compound is defined as the compound which is formed when there is a difference of electronegativities between the atoms. It is also defined as the bond which is formed due to the unequal sharing of electrons between the atoms.
Non-polar compound is defined as the compound which is formed when there is no difference of electronegativities between the atoms or the polarities cancel out.
Hexane [tex](C_6H_{14}), Oil (mixture of hydrocarbons) and carbon tetrachloride [tex](CCl_4)[/tex] all are non polar whereas ethanol is polar due to electronegative difference between hydrogen and oxygen.
1.Draw the born-Haber lattice energy cycle for sodium chloride. Explain the concept of resonance using the nitrate ion structure.
Answer:
1. Born Haber cycle is used to calculate enthalpy of formation of an ionic solid
2. Resonance structures are used to represent the bonding in some chemical species.
Explanation:
The Born–Haber cycle is a method popularly known in chemistry used in computing enthalpy. The enthalpy of formation of an ionic solid cannot be measured directly. The lattice enthalpy refers to the enthalpy change involved in the formation of an ionic compound from gaseous ions the process is exothermic process. A Born–Haber cycle works on the principle of Hess's law. It can be used to calculate the lattice enthalpy by comparing the standard enthalpy change of formation of the ionic compound from the elements to the enthalpy required to make gaseous ions from the elements.
Resonance is an idea introduced by Linus Pauling to explain chemical bonding from the valence bond perspective. The idea of resonance affords us the opportunity to describe the bonding in certain molecules by combining several structures called chemical or canonical structures. The real structure of the specie lie somewhere between the structures indicated by the resonance structures. The resonance structures of the nitrate ion are shown in the image attached.
In this lab, you are to carry out the formation of a Grignard reagent from 1-bromo-benzene andits subsequent reaction with solid carbon dioxide (CO2) followed by acidic workup (using HCl asthe acid). Write the overall reaction and product(s) that you expect.
Answer:
(A). C6H5Br + Mg(in ether) -----------> C6H5MgBr.
(B). C6H5MgBr + O = C = O -----------> C6H5-COO^- Mg^+ Br.
(C). C6H5-COO^- Mg^+ Br + HCl --------> C6H5-COOH + Mg^+Br(OH).
PRODUCTS=> C6H5-COOH and Mg^+Br(OH).
Explanation:
A Grignard reagent is a reagent that/which is an organometallic compound that is R -Mg- X. The R = alkyl, vinyl or allyl and the X = halogens.
It must be noted that an important reaction of Grignard reagent is its reaction with compounds containing the Carbonyl that is -CO functional group and this kind of Reaction is known as a Grignard Reaction.
So, in this question we are told that;
=> "1-bromo-benzene andits subsequent reaction with solid carbon dioxide (CO2) followed by acidic workup (using HCl asthe acid). "
Thus;
(A). C6H5Br + Mg(in ether) -----------> C6H5MgBr.
(B). C6H5MgBr + O = C = O -----------> C6H5-COO^- Mg^+ Br.
(C). C6H5-COO^- Mg^+ Br + HCl --------> C6H5-COOH + Mg^+Br(OH).
2. Points
Which of the following is not a characteristic of a transverse mechanical
wave?
A. It travels at less than the speed of light.
B. It involves displacing the medium perpendicular to the motion of
the wave
C. It looks a little bit like a snake.
D. It is also known as a compression wave.
Answer:
D
Explanation:
Logitudinal waves also known as compression waves.
It involves displacing the medium perpendicular to the motion of the wave is not a characteristic of a transverse mechanical wave. Option B is correct.
What are transverse mechanical waves?A transverse mechanical wave is a disturbance created by it to transfer energy from one point to another. while the proposition happens the particle present within the medium get vibrates.
in a transverse wave, the particle present will vibrate up and down and are perpendicular to the wave's propagation direction. The particles shake in a directional wave in the longitudinal wave propagation.
Therefore, is not a characteristic of a transverse mechanical wave. Option B is correct. It involves displacing the medium perpendicular to the motion of the wave.
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why are the products of light reaction of photosythesis important
Answer: light reaction produces oxygen and water as we know the general importance of oxygen and water they are useful for organism to survive if plants do not produce oxygen then how could we get oxygen from the environment
81. Find the pH of each mixture of acids. a. 0.115 M in HBr and 0.125 M in HCHO2 b. 0.150 M in HNO2 and 0.085 M in HNO3 c. 0.185 M in HCHO2 and 0.225 M in HC2H3O2 d. 0.050 M in acetic acid and 0.050 M in hydrocyanic acid
Answer:
See explanation below
Explanation:
This problem is a little long so I'm gonna be as clear as possible.
a) In this case we have two acids, HBr and HCHO2. Between these two acids, the HBr is the strongest, and does not have a Ka value to dissociate, while HCHO2 do.
In order to calculate pH we need the [H₃O⁺], and in this case, as HBr is stronger, the contribution of the weaker acid can be negligible, therefore, the pH of this mixture will be:
pH = -log[H₃O⁺]
pH = -log(0.115)
pH = 0.93
b) In this case it happens the same thing as part a) HNO₃ is the strongest acid, so the contribution of the HNO₂ which is a weak acid is negligible too, therefore the pH of this mixture will be:
pH = -log(0.085)
pH = 1.07
c) Now in this case, HCHO2 and HC2H3O2 are both weak acids, so to determine which is stronger, we need to see their Ka values. In the case of HCHO2 the Ka is 1.8x10⁻⁴ and for the HC2H3O2 the Ka is 1.8x10⁻⁵. Note that the difference between the two values of Ka is just 10¹ order, so, we can neglect the concentration of either the first or the second acid. We need to see the contribution of each acid, let's begin with the stronger acid first, which is the HCHO2, we will write an ICE chart to determine the value of the [H₃O⁺] and then, use this value to determine the same concentration for the second acid and finally the pH:
HCHO₂ + H₂O <-------> CHO₂⁻ + H₃O⁺ Ka = 1.8*10⁻⁴
i) 0.185 0 0
c) -x +x +x
e) 0.185-x x x
1.8*10⁻⁴ = x² / 0.185-x
As Ka is small, we can assume that "x is small" too, therefore the (0.185-x) can be rounded to just 0.185 so:
1.8*10⁻⁴ = x²/0.185
1.8*10⁻⁴ * 0.185 = x²
x² = 3.33*10⁻⁵
x = 5.77*10⁻³ M = [H₃O⁺]
Now that we have this concentration, let's write an ICE chart for the other acid, but taking account this concentration of [H₃O⁺] as innitial in the chart, and solve for the new concentration of [H₃O⁺] (In this case i will use "y" instead of "x" to make a difference from the above):
HC₂H₃O₂ + H₂O <--------> C₂H₃O₂⁻ + H₃O⁺ Ka = 1.8x10⁻⁵
i) 0.225 0 5.77x10⁻⁶
c) -y +y +y
e) 0.225-y y 5-77x10⁻³+y
1.8x10⁻⁵ = y(5.77x10⁻³+y) / 0.225-y ---> once again, y is small so:
1.8x10⁻⁵ = 5.77x10⁻³y + y² / 0.225
1.8x10⁻⁵ * 0.225 = 5.77x10⁻³y + y²
y² + 5.77x10⁻³y - 4.05x10⁻⁶ = 0
Solving for y:
y = -5.77x10⁻³ ±√(5.77x10⁻³)² + 4*4.05x10⁻⁶ / 2
y = -5.77x10⁻³ ±√4.95x10⁻⁵ / 2
y = -5.77x10⁻³ ± 7.04x10⁻³ / 2
y₁ = 6.35x10⁻⁴ M
y₂ = -6.41x10⁻³ M
We will take y₁ as the value, so the concentration of hydronium will be:
[H₃O⁺] = 5.77x10⁻³ + 6.35x10⁻⁴ = 6.41x10⁻³ M
Finally the pH for this mixture is:
pH = -log(6.41x10⁻³)
pH = 2.19
d) In this case, we have the same as part c, however the Ka values differ this time. The Ka for acetic acid is 1.8x10⁻⁵ while for HCN is 4.9x10⁻¹⁰. In this ocassion, we the difference in their ka is 10⁵ order, so we can neglect the HCN concentration and focus in the acetic acid. Let's do an ICE chart and then, with the hydronium concentration we will calculate pH:
HC₂H₃O₂ + H₂O <--------> C₂H₃O₂⁻ + H₃O⁺ Ka = 1.8x10⁻⁵
i) 0.050 0 0
c) -y +y +y
e) 0.050-y y y
1.8*10⁻⁵ = y² / 0.050-y
As Ka is small, we can assume that "y is small" too
1.8*10⁻⁵ = y²/0.050
1.8*10⁻⁵ * 0.050 = y²
y² = 9*10⁻⁷
y = 9.45*10⁻⁵ M = [H₃O⁺]
Finally the pH:
pH = -log(9.45x10⁻⁵)
pH = 3.02
A base has a molarity of 1.5 M with respect to the hydroxyl ion (OH-) concentration. If 7.35 cm³ of this base is taken and diluted to 147 cm³, then what is the concentration of the hydroxyl ion. How many moles of hydroxyl ion are there in the 7.35 cm³? In the 147 cm³?
Answer:
0.077M is the concentration of the hydroxyl ion
Explanation:
If 7.35 cm3 of this base is take and diluted to 147 cm3, then what is the concentration of the hydroxyl ion?
Use the dilution equation:
M1V1 = M2V2
M1 * 147cm³ = 1.5 M * 7.35 cm³
M1 = 1.5 M * 7.35 cm³ / 147 cm³
M1 = 0.077 M
0.077M is the concentration of the hydroxyl ionHow many moles of hydroxyl ion are there in the 7.35 cm3?
1000 cm³ contains 1.5 mol OH- ions
7.35 cm³ contains : 7.35 cm³ / 1000 cm³ *1.5 mol
= 0.011025 mol
Answer correct to 2 significant digits = 0.011 mol OH- ions.