Answer:
20
Explanation:
Because mass number is equal to Atomic number.
A certain sample of element Z contains 60% of 69Z and 40% of 71Z. What is the relative atomic mass of element Z in this sample?
Answer:
The relative atomic mass of element Z in this sample is 70.
Explanation:
The relative atomic mass of element Z in this sample is 69.6.
Which of the following halogens is darkest in colour?
Select one:
a. l
b. Br₂
c. F2₂
d. Cl₂
I₂ is the halogens which is darkest in colour than other.
What is halogen?Halogens are the elements which belongs to group 17. Group 17 elements are known as halogens. They are highly electronegative in nature.
The last electronic configuration is ns2 np5. Since, one electron is less to get stable electronic configuration. Therefore, they accept one electron and get stable electronic configuration.
Why halogens are dark in colour?As we move down the group, the darkness of colour increases. This is due to ionization energy which decreases as we move down the group. This is due to increase in the atomic size and decrease in nuclear form which further make high energy level to absorb lesser light and reflects deepen colour on moving down the group. Due to which they appears dark. Therefore, option A is the correct option.
Thus, we can concluded that I₂ is the halogens which is darkest in colour than other.
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how does a phosphorus atom become a phosphide ion with a 3- charge? why is your answer correct?
Ions can be made by single element or covalently bonded group of elements. The covalently bonded group of elements is called polyatomic ions or polyatomic atoms. Therefore, to become P³⁻, phosphorous has to gain 3 electrons in its p orbital.
What is Ions?Any species that contain charge whether it is positive charge or negative charge is called ions. The example of polyatomic ions are sulfate, phosphate, nitrate etc.
Cation is the species that loose electron and attain positive charge while anion is a species which gain electron and attains negative charge so when anion and cation combine in fixed ration the the overall charge of the molecule is zero that is molecule is neutral, the charge over cation and anion is also called oxidation state.
The electronic configuration of phosphorous is Ne 3s² 3p³. To become P³⁻. Phosphorous has to gain 3 electrons in its p orbital.
Therefore, to become P³⁻, phosphorous has to gain 3 electrons in its p orbital.
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For 8.68×10−3 M LiOH, determine [OH−] and [H3O+].
Taking into account the definition of pH and pOH, for 8.68×10⁻³ M LiOH, the [OH⁻] is 8.68×10⁻³ M and the [H₃O⁺] is 1.148×10⁻¹² M.
Definition of pHpH is a measure of acidity or alkalinity that indicates the amount of hydrogen ions present in a solution or substance.
The pH is defined as the negative base 10 logarithm of the activity of hydrogen ions, that is, the concentration of hydrogen ions or H₃O⁺:
pH= - log [H⁺]= - log [H₃O⁺]
Definition of pOHSimilarly, pOH is a measure of hydroxyl ions in a solution and is expressed as the logarithm of the concentration of OH⁻ ions, with the sign changed:
pOH= - log [OH⁻]
Relationship between pH and pOHThe following relationship can be established between pH and pOH:
pOH + pH= 14
Definition of strong baseA strong base is a base that completely dissociates in aqueous solution. That is, in the ionization process they are completely transformed into cations or positive ions and into anions or negative ions, all concentrations being equal.
[H₃O⁺] and [OH⁻] in this caseLiOH is a strong base, so [LiOH]=[OH⁻]= 8.68×10⁻³ M
Replacing in the definition of pOH:
pOH= - log 8.68×10⁻³ M
Solving
pOH= 2.06
So, pH is calculated as:
pH + 2.06= 14
pH= 14 - 2.06
pH= 11.94
Replacing this value in the definition of the pH:
- log [H₃O⁺]= 11.94
Solving:
[H₃O⁺]= [tex]10^{-11.94}[/tex]
[H₃O⁺]= 1.148×10⁻¹² M
In summary, the [OH⁻] is 8.68×10⁻³ M and the [H₃O⁺] is 1.148×10⁻¹² M.
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Q4.
A chemical is soluble in water but insoluble in benzene. As a consequence, benzene
may be used to determine its density. The density of benzene is 0.879/g/L. Calculate the
density of the sample.
(a) Weight of empty flask
(b) Weight of flask + sample
(c) Weight of flask + sample + benzene to fill
(d) Weight of flask + benzene (without sample)
Calculate the percentage error in the density of the sample.
8.862 +0.002 g
10.986 ± 0.002 g
30.086 +0.002 g
29.172 0.002 g
Answer:
c 8id
Explanation:
A 25. 0 ml sample of 0. 150 m hydrofluoric acid is titrated with a 0. 150 m naoh solution. What is the ph at the equivalence point? the ka of hydrofluoric acid is 3. 5 × 10-4.
Answer:
............
.............................
Use the molar bond enthalpy data in the table to estimate the value of Δ∘rxn for the equation?
C2H4(g)+HBr(g)⟶C2H5Br(g)
The bonding in the molecules is shown.
From the values of bond enthalpy shown, the enthalpy of the reaction is -263 kJ/mol.
What is the enthalpy of the reaction?We know that the enthalpy of the reaction has to do with the energy that has been lost or gained in the reaction. We know that in the course of a chemical reaction, thee is the breaking and the forming of bonds.
Looking at the reaction, we know that the enthalpy of the reaction is to be obtained as the difference between the total bond energies of the products and the total bond energies of the reactants.
The bond energies present are;
C=C - 598 kJ/mol
C-C - 346 kJ/mol
C -H - 416 kJ/mol
H -Br - 366 kJ/mol
C - Br - 285 kJ/mol
Then we have;
[1(346) + 5(416) + 1(285)] - [1( 598) + 4(416) + 1(346) + 1( 366)]
[346 + 2080 + 285] - [598 + 1664 + 346 + 366]
2711 - 2974
= -263 kJ/mol
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What is the answer to AB → A + B.
Answer: Decomposition reaction
Explanation:
This reaction type is a decomposition reaction. The single compound reactant is "breaking up" into two or more products.
How many equivalents of Mg2+ are present in a solution that contains 2.60 moles of Mg2+ ?
Answer:
Science. Chemistry. Chemistry questions and answers. How many equivalents of Mg2+ are present in a solution that contains 2.65 moles of Mg2+ ? Express your answer using three …
Expert Answer. 100% (5 ratings) Number of equivalents of an ion …. View the full answer. Transcribed image text: Question 4 (0.5 points) How many equivalents of Mg2+ are present in …
how many equivalents of Mg2+ are present in a solution that contains 2.75 mol of Mg2+?
A:
5.50 eq
Explanation:
Protactinium-231 undergoes alpha decay as shown:
Enter the appropriate values for A and Z and the chemical symbol for X
The appropriate values for A and Z and the chemical symbol for X in the alpha decay of protactinium-231 is
A = 227Z = 89X = AcWhat is alpha decay?Alpha decay is a radioactive decay by emitting an alpha particle, which is a positively charged nucleus of a helium-4 atom (consisting of two protons and two neutrons), emitted as a consequence of radioactivity.
Alpha has a symbol of α-particle. According to this question, protactinium-231 undergoes alpha decay, which means that it will lose 4 in its mass number and 2 in its atomic number.
231 - 4 = 227
91 - 2 = 89
The element that will be formed from the alpha decay will have a mass number of 227 and an atomic number of 89.
The element with an atomic number of 89 is actinium with chemical symbol Ac.
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Explain how bright-line emission spectra could be used to perhaps identify which atoms are present in an unknown gas sample
Since each element has a distinct range of energy levels, the lines in an emission spectrum will be bright while those in an absorption spectrum would be dark. This makes spectra useful for identifying the various elements in a sample.
How can atomic spectra be used to identify elements?A tip: Atomic emission spectra depict electrons returning to lower energy levels within an atom. Because of the nature of quantum physics, only particular discrete energies are capable of being absorbed and emitted by electrons. Each element's electron orbitals are arranged in a particular way.Complete answer: In atomic spectroscopy, electromagnetic radiation that is absorbed and emitted by atoms is investigated. Since distinctive elements have distinctive spectra, atomic spectroscopy—more precisely, the electromagnetic spectrum or mass spectrum—is used to ascertain the makeup of the elements. Each element's energy level is distinct due to the fact that each one's nucleus contains a different amount of protons. Since each element has a distinct range of energy levels, the spectra can be used to identify the various elements in a sample. In emission spectra, bright lines that correspond to the difference in the energy levels of the elements will appear, but in absorption spectra, the lines will be dark.To Learn more About emission spectrum refer to :
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If He gas has an average kinetic energy of 5130 J/mol under certain conditions, what is the root mean square speed of O2 gas molecules under the same conditions?
The kinetic energy of the oxygen gas under the same condition is the same as that of helium.
What is the root mean square speed of oxygen?We know that the kinetic energy of a gas depends on the temperature of the molecules of the gas. Temperature is the measure of the average kinetic energy of the molecules of the gas.
When we know that we have two gases, what would determine the average kinetic energy of the molecules of the gas would only be the temperature of the gas. Thus irrespective of the molar masses of the gases, they would have the same kinetic energy at the same temperature.
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An aqueous solution of sodium phosphate is added to an aqueous solution of strontium chloride. Strontium phosphate is precipitated. What is the net ionic equation
The net ionic equation is;
[tex]2PO_{4} ^{3-} (aq) + 3Sr^{2+} (aq) ----- > Sr_{3} (PO_{4})_{2} (s)[/tex]
What is the net ionic equation?The net ionic equation has to do with the equation that shows the ions that have undergone changes in the system. We know that the first step as we are tying to obtain the net ionic equation must be to write down the molecular equation of the reaction which we have have done here as
;[tex]2Na_{3} PO_{4} (aq) + 3SrCl_{2} (aq) ----- > Sr_{3} (PO_{4})_{2} (s) + 6NaCl(aq)[/tex]
We can see that the ions that had to be changed in the process are the phosphate ion and the phosphate ion. It was the both ions that were combined to obtain the precipitate thus they are more in the solution and they have to appear in our net ionic equation for this reaction.
Thus, in a nut shell, the ions that are going to occur in the net ionic equation are the ions that were combined as we can see to give the precipitate here.
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What are the two layers that are formed when you mix water and Isopropanol
According to the concept of solubility, isopropanol is miscible with water and hence there is one layer that is formed when water and isopropanol are mixed.
What is solubility?Solubility is defined as the ability of a substance which is basically solute to form a solution with another substance. There is an extent to which a substance is soluble in a particular solvent. This is generally measured as the concentration of a solute present in a saturated solution.
The solubility mainly depends on the composition of solute and solvent ,its pH and presence of other dissolved substance. It is also dependent on temperature and pressure which is maintained.Concept of solubility is not valid for chemical reactions which are irreversible. The dependency of solubility on various factors is due to interactions between the particles, molecule or ions.
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If you mix 30 mL of cold water with 70 mL of hot water in a calorimeter, and the temperature of the cold water increases by 1.9°C, then how much heat (in joules) did the cold water absorb (only enter the number, not units, and assume the density of water to be 1.00g/mL, and the specific heat capacity of water to be 4.184 J/g-°C)?
70 mL of hot water are required. Increase in the temperature of the cold water, where water's specific heat capacity is 4.184 J/g and its density is 1.00 g/mL. Here, the mass of the cold water is equal to 30 mL times the density of one gram per milliliter, or 30g.
What is a calorimeter used for?A instrument is a machine that calculates how much heat is generated during a physical or chemical process. For instance, when an exergonic reaction takes place in solutions in a measuring device, the solution absorbs the heat created by the process, raising its temperature.
The calorimeter is used where?To gauge a body's temperature fluctuations, a calorimeter is utilized. Calculating enthalpy, stability, heat capacity, and other thermochemical quantities often involves the use of calorimetry.
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A student measures the length of a book to be 32.4 cm. The accepted value of the length is 32.9 cm. What is the percent error of the student’s measurement?
The percent error of the student’s measurement is 98.48%
While doing any experiment or any calculation we usually calculate the estimated result or value that needs to come at the end of the reaction and that is called as theoretical value. But once the experiment is completed the value that we get is not the same as that of theoretical value and this value is called as the experimental value.
To understand the error that had happened during the experiment we find out the percent error and the formula for it is as follows
Percent error = Experimental value × 100
Theoretical value
When we use the same formula for the above given case we can see that the expected measurement was supposed to be 32.9 but the student measure it to be 32.4 so the percent error here is
= 32.4 × 100 ⇒ 98.48%
32.9
Hence the percent error in calculation is 98.48%
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PLEASE HELP ITS A TEST QUESTION!!!! The particles that make up gases are close or apart from each other?
Why is it not necessary to test the reactivity of the elemental metals with solutions of the same metal ion?
It is not necessary to test the reactivity of the elemental metals with solutions of the same metal ion because it won't react with itself.
What is Reactivity?
This is referred to as the relative capacity or how readily a substance undergoes a chemical reaction.
Reactivity of elements are dependent on various types of parameters such as the number of valence electrons, shells etc and can be tested with other substances. However, it can't be tested with the solutions of the same metal ion because no reaction will occur thereby making it the most correct reason in this scenario.
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determine each of the following of 0.065 M KOH solutin. milliliters of the KOH required to neutralize 40.0 mL of a 0.035 M H2sO4 solution express in 2 sig figs
The volume of the KOH required to neutralize 40.0 mL of a 0.035 M H2sO4 solution is 0.0215 L.
Concentration is the abundance of a constituent divided by way of the overall volume of an aggregate. several sorts of mathematical descriptions may be outstanding: mass concentration, molar concentration, variety concentration, and extent awareness.
Given
V1 =?
C₁ = 0.65 M
C₂ = 0.035 M
n -2
V2 = 40 ml = 0.04 L
C₁V₁ = C₂V₂
V₁ = C₂V₂/ C₁
= 0.035 * 0.04 / 0.065
= 0.0215 L
The concentration of a substance is the quantity of solute found in a given amount of solution. Concentrations are normally expressed in terms of molarity, defined because of the variety of moles of solute in 1 L of answer.
The Concentration of an answer is a measure of the quantity of solute that has been dissolved in a given amount of solvent or answer. A concentrated answer is one that has a rather huge quantity of dissolved solute.
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A 0.683 g impure sample of strontium hydroxide is dissolved in 120 ml of 0.1010 M HCl. Titration of the excess with 0.1020 M NaOH required 36.6 ml to reach the equivalence point. Calculate the percent purity of the sample.
The percent purity of strontium hydroxide in the mass of the given sample is 74.7%.
What is the percent purity of a substance?The percent purity of a substance is the ratio of the actual amount of a substance present in a sample and the ratio of the whole amount of the sample.
Percent purity = (mass of pure sample/ mass of impure sample) * 100%Equation of reaction: Sr(OH)₂ + 2 HCl ---> SrCl₂ + 2 H₂O
The mass of the pure strontium hydroxide is calculated as follows:
moles of initial HCl sample = 0.1010 * 120 mL * 1 L / 1000 mL
moles of initial HCl sample = 0.01212 moles
Moles of HCl that reacted with NaOH = 0.1020 * 36.6 * 1 L / 1000 mL
Moles of HCl that reacted with NaOH = 0.00373 moles
moles of HCl that reacted with strontium hydroxide = 0.01212 - 0.00373
moles of HCl that reacted with strontium hydroxide = 0.00839 moles
Moles of strontium hydroxide that reacted with HCl = 0.00839/2 moles
Mass of strontium hydroxide that reacted with HCl = 0.00839/2 moles * 121.63 g/mol
Mass of strontium hydroxide that reacted with HCl = 0.510 g
Percent purity = 0.510/0.683 * 100 %
Percent purity = 74.7%
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5.Human Medullary Patterns has three types:
1.__________________ regular interruption
2._____________________ medullary canal.
3.____________________ interruption irregular
Forensic
Answer:
Forensic anthropology is the study of human remains in order to solve crimes or to determine the identity of a deceased individual.
Explanation:
8. At STP, 4.00 L of a pure gaseous substance has a mass of 10.0 grams. The molecular weight of this substance is?
At STP, 4.00 L of a pure gaseous substance has a mass of 10.0 grams. The molecular weight of this substance is is 56 g/mol.
The ideal gas equation is here:
P V = n RT
where,
P = pressure = 1 atm
V = volume = 4 L
R = 0.082 L atm /K mol
T = temperature = 273 K
n = (1 × 4 ) / (0.082 × 273)
n = 0.178 mol
mass = 10 g
molecular weight = moles / mass
= 10 / 0.178
= 56 g/mol
Thus, At STP, 4.00 L of a pure gaseous substance has a mass of 10.0 grams. The molecular weight of this substance is is 56 g/mol.
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Chemistry help would be greatly appreciated
The percent by mass of the chromium is 32.1 %.
What is the percent by mass?The term percent by mass has to do with the ratio of the mass of a particular component of the component to the total mass of the compound multiplied by hundred. Let us recall that a percent must involve hundred.
Now we have;
Mass of Cr = 16.05
Total mass of the sample = 50 g
We now have;
Mass of Cr/ Total mass * 100/1
= 16.05/50 g * 100/1
= 32.1 %
Hence, from the total sample, we have about 32.1 % of chromium.
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Why should you never shake a test tube containing reagents by covering its mouth with a finger?
The reagents in a test tube should never be shaken by keeping a finger on its mouth because, you would contaminate the other reagents when same finger is used for other test tubes. Instead you can use a shaker in the laboratory.
What is a shaker in laboratory?
Shaker is a laboratory equipment which can be used to blend, mix or agitate samples in the tube. There are different types like vortex shaker, orbital shaker, platform shaker and incubator shaker.
The samples in the test tubes can easily get contaminated when it is shaken with a finger. Also, if you are sensitive to some chemicals your hands can burn or may cause irritation if shaker is not being used in shaking.
Therefore, shaker is a better option to mix the reagents in a test tube than shaking the test tube by closing its mouth with a finger.
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Manganese, Mn, forms two ions, one with a 2+ charge and one with a 3+ charge. What is the formula for manganese (II) sulfide?
Manganese, Mn, forms two ions, one with a 2+ charge and one with a 3+ charge. the formula for manganese (II) sulfide is MnS.
The manganese atomic number is 25. the manganese is the metal . metal have tendency to donate valence electron. manganese donate 2 electrons and form Mn⁺². The sulfur atomic number is 16. sulfur is nonmetal and tendency to accept electrons. sulfur accepts electrons and form S²⁻. The manganese and sulfur thus combines and form ionic compound. the formula for ionic compound manganese(II)sulfide is MnS
Thus, Manganese, Mn, forms two ions, one with a 2+ charge and one with a 3+ charge. the formula for manganese (II) sulfide is MnS.
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Which name best describes an enzyme that catalyzes a reaction involving the reduction of hydrogen peroxide with the oxidation of a second molecule of hydrogen peroxide?.
Catalase best describes an enzyme that catalyzes a reaction involving the reduction of hydrogen peroxide with the oxidation of the second molecule of hydrogen peroxide.
Catalase is a common enzyme determined in almost all dwelling organisms exposed to oxygen (consisting of microorganisms, vegetation, and animals) which catalyzes the decomposition of hydrogen peroxide to water and oxygen. it's by far a totally crucial enzyme in defending the cell from oxidative damage by reactive oxygen species (ROS).
An enzyme is an organic catalyst and is sort of usually a protein. It quickens the fee of a selected chemical reaction within the cellular. The enzyme isn't destroyed at some stage in the reaction and is used again and again. Enzymes are categorized into six classes consistent with the form of reaction catalyzed: Oxidoreductases, transferases, hydrolases, lyases, ligases, and isomerases.
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List the elements from least to greatest atomic radius: Zinc (Zn), Oxygen (O), Rubidium (Rb)
Answer:
1 ) Zinc
2 ) Oxygen
3 ) Rubidium
Explanation:
Zinc ( Zn ) - r = 140 pm
Oxygen ( O ) - r = 152 pm
Rubidium ( Rb ) - r = 303 pm
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A sample solution containing sulfate ions (SO42-) was analyzed and was found to contain 5 mol of sulfate ions (SO42-).
Calculate the equivalent of sulfate ions (SO42-) present in the solution.
Equivalent of sulfate ions = 4.00 EqSO4^2−
1) equivalent weight of sulphate = 96.0636/2
= 48.0328 g/equivalent
2) 2 mol will have a weight of = 2*96.0636 = 192.1272 g
3) so the equivalent of sulphate = 192.1272/48.0328
= 3.999, round it up to 4.00
How come sulphate is SO42?Sulfur and oxygen atoms make up the majority of the sulphate ion's mass. Four oxygen atoms that are placed at equal intervals around the centre sulphur atom in this structure. In terms of bonding, two oxygen atoms make S=O bonds, while the other two form S-O bonds.
Two double bonds and two single bonds with O make up the more stable structure of SO42-, however the single bonds have a formal charge of -1.
An insoluble precipitate of BaSO4 forms when aqueous barium chloride is introduced to an acidified solution containing sulphate ions. This precipitate, which is white in colour, proves that sulphate is present.
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What is the percent by mass of hydrogen in sulfuric acid?
Answer: 2.06%
Explanation:
The chemical formula for sulfuric acid is H₂SO₄.
Find the molar mass of the whole compound:
Hydrogen(H) ≈ 1.01Sulfur(S) ≈ 32.07Oxygen(O) ≈ 162(1.01) + 32.07 + 4(16) = 98.02 g/mol
The percent composition by mass of hydrogen can be calculated as:
[tex]\frac{2.02}{98.02}*100=0.0206*100=2.06[/tex]
Write a balanced equation for the reaction that occurs when a piece of magnesium is dropped into hydrochloride acid (HCI) solution forming magnesium chloride (MgCl2) in aqueous state and hydrogen gas
Answer:
The balanced chemical equation is:
Mg_((s))+ 2HCl_((aq))rarrMgCl_(2(aq)) + H_(2(g)
Explanation:
The reaction between magnesium and hydrochloric acid combine to form a salt of magnesium chloride and release hydrogen gas. This single replacement reaction is a classic example of a metal reacting in an acid to release hydrogen gas.
