The energy from 0.015 moles of octane was used to heat 250 grams of water. The temperature of the water rose from 293.0 K to 371.2 K. What is the enthalpy of combustion of octane? The specific heat capacity of water is 4.18 J/K g.
A. -5448 kJ/mol
B. 1226 kJ/mol
C. -1226 kJ/mol
D. 293.25 kJ/mol
Answer:
A.) -5448 kJ/mol
Explanation:
I got it correct on founders edtell
In an ecosystem, why can only one species fill an ecological niche?
Answer:
Explanation:es porque las especies con nichos idénticos tienen las mismas necesidades, lo que significa que competirían exactamente por los mismos recursos.
Give some examples of how ultraviolet rays can be used
Answer:
One of the most common ways of producing UV light is passing an electric current through vaporized mercury or some other gas. This type of lamp is commonly used in tanning booths and for disinfecting surfaces. The lamps are also used in black lights that cause fluorescent paints and dyes to glow.Explanation:
⚠️SOMEONE PLEASE HELP⚠️
Which describes two phases in dynamic equilibrium?
O A. Molecules in one phase continually change to the other.
O B. The total number of molecules must be equal in each phase.
O C. Molecules do not change from one phase to the other.
O D. The total number of molecules in each phase stays constant.
Answer:
The total number of molecules in each phase stays constant
Explanation:
i just took the test and got it right.
In the dynamic equilibrium between 2 phases, the total number of molecules in each phase stays constant (Option D).
When does dynamic equilibrium occur?Dynamic equilibrium occurs when the direct and reverse rates are equal and the concentrations remain constant over time.
Which describes two phases in dynamic equilibrium?
A. Molecules in one phase continually change to the other. NO. Molecules in both phases continually change.B. The total number of molecules must be equal in each phase. NO. This is not necessarily true.C. Molecules do not change from one phase to the other. NO. This would be a static equilibrium.D. The total number of molecules in each phase stays constant. YES. Since the forward and reverse rates are equal.In the dynamic equilibrium between 2 phases, the total number of molecules in each phase stays constant (Option D).
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A 2.575 g piece of gold (specific heat = 0.129 J/g°C) at a temperature of 75°C is placed into cold water at 10°C. If the gold loses 10.0 J of energy, what is its final
temperature in the water? Enter your answer to the
nearest whole number of °C.
Answer:
The final temperature of the mixture is 44.9°C
Explanation:
Mass of the substance (gold) = 2.575g
Specific heat capacity of gold = 0.129J/g°C
Initial temperature (T1) = 75°C
Final temperature (T2) = ?
Energy lost = 10J
Heat energy(Q) = MC∇T
Q = heat energy (in this case lost)
M = mass of the substance
C = specific heat capacity of the substance
∇T = change in temperature of the substance = (T2 - T1)
Q = MC∇T
Q = MC(T2 - T1)
-10 = 2.575 × 0.129 × (T2 - 75) energy is -ve because it was energy lost.
-10 = 0.3321 × (T2 - 75)
-10 = 0.3321T2 - 24.9075
Collect like terms
0.3321T2 = 24.9075 - 10
0.3321T2 = 14.9075
T2 = 14.9075 / 0.3321
T2 = 44.88
T2 = 44.9°C
The final temperature of the mixture is 44.9°C
let's consider the effectiveness of two antacids to illustrate how chemical calculations can be important in daily life. Baking soda NaHCO3, is often used as an antacid. It neutralizes excess hydrochloric acid sereted by stomach. The balanced equation for the reaction is NaHCO3(s)+HCl(aq)=H20(l)+CO2(g). Milk of magnesia, which is an aqueous suspension of magnesium hydroxide, Mg(OH)2(s)+2HCl(aq)=2H20(l)+MgCl2(aq), Which anatacid can consume the most stomach acid, 1.00g of NaHCO3,or 1.00g of Mg (OH)2?
Answer:
Milk of Magnesia would consume the most stomach acid at almost 3 times the amount as baking soda.
Explanation:
Baking Soda = NaHCO3(s)+HCl(aq)=H20(l)+CO2(g)
NaHCO3 Molar mass of 84.007 g/mol
0.012 Moles of NaHCO3 and since an equal ratio of HCl is required
we therefore neutralize 0.012 Moles of HCl
Milk of magnesia = Mg(OH)2(s)+2HCl(aq)=2H20(l)+MgCl2(aq)
Mg(OH)2(s) Molar mass: 58.3197 g/mol
0.017 Moles of Mg(OH)2 and the ratio is 2:1, so 2 moles for each 1 mole of Mg(OH)2, so we need 0.034 Moles of HCl
The density was of a solution of sulfuric acid is 1.285g/cm3 and it is 38.08% (by weight) acid. How many millimeters of the acid solution do you need to supply 125 grams of sulfuric acid?
Answer:
255.5cm³
Explanation:
A solution that is 38.08 % by weight has 38.08g of sulfuric acid per 100g of total solution. Thus, mass of solution you need to obtain 125g is:
125g H₂SO₄ × (100g solution / 38.08g H₂SO₄) = 328.3g of solution
As density of the solution is 1.285g / cm³, the volume of 328.3g is:
328.3g × (1cm³ / 1.285g) = 255.5cm³
An elements mass number is made up of the number of ____ in the nucleus.
protons and neutrons
electrons and neutrons
protons and electrons
atoms and molecules
Answer:
The answer is protons and nuetrons
Explanation:
The electron dot diagram for a neutral atom of chlorine (atomic number 17) is shown below.
Which of the following symbols represents a chlorine ion with a stable arrangement of eight valence electrons?
A. 35Cl1-
B. 35Cl2-
C. 35Cl1+
D. 35Cl
Answer:
A. 35Cl1-
Explanation:
Chlorine needs 1 more electron to have full octet thus will take 1 electron and possess a -1 charge.
WILL MARK BRAINLIEST IF GOOD EXPLANATION...
Ethyl acetate is a sweet-smelling solvent used in varnishes and fingernail polish remover. It is produced industrially by heating acetic acid and ethanol
together in the presence of sulfuric acid, which is added to speed up the
reaction. The ethyl acetate is distilled off as it is formed. The equation for the
process is as follows.
CH3COOH + CH3CH2OH --> CH3COOCH2CH3 + H2O
Determine the percentage yield in the following cases:
a. 68.3 g of ethyl acetate should be produced but only 43.9 g is recovered.
b. 0.0419 mol of ethyl acetate is produced but 0.0722 mol is expected. (Hint:
Percentage yield can also be calculated by dividing the actual yield in moles
by the theoretical yield in moles.)
c. 4.29 mol of ethanol is reacted with excess acetic acid, but only 2.98 mol of
ethyl acetate is produced.
d. A mixture of 0.58 mol ethanol and 0.82 mol acetic acid is reacted and 0.46
mol ethyl acetate is produced. (Hint: What is the limiting reactant?)
Answer:
a) 64.27%
b) 58%
c) ethanol is the limiting reactant
d) ethanol is the limiting reactant
Explanation:
We have to note that the expected yield is the theoretical yield while the actual mass or amount of product formed is the actual yield.
a) theoretical yield=68.3g
Actual yield= 43.9 g
Percentage yield= 43.9/68.3 ×100
Percentage yield= 64.27%
b) theoretical yield= 0.0722 moles
Actual yield = 0.0419
Percentage yield= 0.0419/0.0722 × 100
Percentage yield= 58%
c) note that the limiting reactant yields the least number of moles of product
Ethanol will be the limiting reactant since it is not present in excess.
d) from the reaction equation;
1 mole of acetic acid produces 1 mole of ethyl acetate
0.58 moles of ethanol produces 0.58 moles of ethyl acetate
1 mole of acetic acid yields 1 mole of ethyl acetate
Hence 0.82 moles of acetic acid yields 0.82 moles of ethyl acetate
Hence ethanol is the limiting reactant.
Level 3- How is tooth decay related to pH?How can it be prevented?
Answer:
A lower pH of the mouth creates bad bacteria that eventually lead to decay of the tooth.
It can be prevented by avoiding food that causes acidity.
Explanation:
Tooth decay is caused by the pH level in the mouth dropping below 5.5, meaning it is acidic. It can be prevented by brushing your teeth as toothpaste is an alkali which will neutralise the pH level in your mouth.
Hope this helps
50cm3 of sodium hydroxide solution was titrated against a solution of sulfuric acid. The concentration of the sodium hydroxide solution was 20g/dm3. Work out the concentration of the acid in grams per litre if it took 25cm3 of acid to completely neutralise the alkali. The relative molecular mass of sulfuric acid is 98.
Answer:
49 g/L is the concentration of the acid
Explanation:
Firstly, we proceed to write the equation of reaction.
2NaOH + H2SO4 ——-> Na2SO4 + 2H2O
We can see that 1 mole of the base reacted with two moles of the acid.
kindly note that dm^3 is same as liter
Firstly, we need to get the concentration of the reacted sulphuric acid in g/L
we use the simple titration equation below;
CaVa/CbVb = Na/Nb
From the question;
Ca = ?
Va = 25 cm^3
Cb = 20 g/L
we convert this to concentration in mol/L
Mathematically, that is concentration in g/L divided by molar mass in g/mole
molar mass of NaOH = 40 g/mol
so we have; 20g/L / 40 = 0.5 mol/L
Vb = 50 cm^3
Na = 1
Nb = 2
Where C represents concentrations, V volumes and N , number of moles
Now, substitute the values;
Ca * 25/0.5 * 50 = 1/2
25Ca/25 = 0.5
So Ca = 0.5 mol/L
Now to get the concentration of H2SO4 in g/L
What we do is to multiply the concentration in mol/L by molar mass in g/mol
That would be 0.5 * 98 = 49 g/L
The concentration of the acid in grams per litre is 49g/L
From the question,
We are to determine concentration of the sodium hydroxide solution.
First, we will write a balanced chemical equation for the reaction.
The balanced chemical equation for the reaction is
2NaOH + H₂SO₄ → Na₂SO₄ + 2H₂O
This means,
2 moles of NaOH is required to completely neutralize 1 mole of H₂SO₄
From the formula
[tex]\frac{C_{A}V_{A} }{C_{B}V_{B} }=\frac{n_{A} }{n_{B} }[/tex]
Where
[tex]C_{A}[/tex] is the concentration of acid
[tex]C_{B}[/tex] is the concentration of base
[tex]V_{A}[/tex] is the volume of acid
[tex]V_{B}[/tex] is the volume of base
[tex]n_{A}[/tex] is the mole ratio of acid
[tex]n_{B}[/tex] is the mole ratio of base
From the question
[tex]V_{A}= 25 \ cm^{3}[/tex]
[tex]C_{B} = 20 \ g/dm^{3}[/tex]
Convert this to mol/dm³
Molar mass of NaOH = 40 g/mol
Using the formula
[tex]Concentration\ in \ mol/dm^{3} =\frac{Concentration\ in \ g/dm^{3}}{Molar\ mass}[/tex]
∴ Concentration of the NaOH in mol/dm³ = [tex]\frac{20}{40}[/tex]
Concentration of the NaOH in mol/dm³ = 0.5 mol/dm³
∴ [tex]C_{B} = 0.5 \ mol/dm^{3}[/tex]
and
[tex]V_{B} = 50 \ cm^{3}[/tex]
From the balanced chemical equation
[tex]n_{A} = 1[/tex]
[tex]n_{B} = 2[/tex]
Putting the parameters into the formula, we get
[tex]\frac{C_{A} \times 25}{0.5 \times 50}= \frac{1}{2}[/tex]
Now, this becomes
[tex]2 \times 25 \times C_{A}=0.5 \times 50 \times 1[/tex]
Then, we get
[tex]50 C_{A} = 25[/tex]
∴ [tex]C_{A} = \frac{25}{50}[/tex]
[tex]C_{A} = 0.5 \ mol/dm^{3} = 0.5 \ mol/L[/tex]
Now, we will determine the concentration in g/L
From the formula,
Concentration in g/L = Concentration in mol/L × Molar mass
From the question,
Molar mass of sulfuric acid = 98
∴ Concentration of the acid in g/L = 0.5 × 98
Concentration of the acid in g/L = 49 g/L
Hence, the concentration of the acid in grams per litre is 49g/L
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Calculate the number of moles of MgO if the mass of MgO (magnesium oxide) is 50 g?
Please help... I will mark the answer with brainlist...
Answer:
1.24mol
Explanation:
m(MgO)=50g
molar mass=40.30g/mol (i search in google coz dosnt have book)
n=mass/molar mass
=50/40.30
=1.24mol
1. Look at yourself in the front of the spoon (the side where the food sits). What do you see?
The you see the image
Answer:
If you look at yourself in the front of the spoon, you see that the mirror forms an inverted real image.
Explanation:
The word 'concave' means to bend inwards.
A curved mirror is a mirror that has a curved reflecting surface.
The front side of the spoon is just like a concave mirror. If you look at yourself in the front of the spoon, you see that the mirror forms an inverted real image.
Concave mirrors produce real inverted image of an object only if it is placed further away from the mirror than the focal point.
Answer:
It shows me upside down like a ghost. OoooOooh
Explanation:
Boo
where are people mostly exposed to chemicals?
Answer:
people are mostly exposed to chemicals through their nose, mouth, eyes, and ears
Explanation:
they are the easiest way for anything, bad or good, to enter the body because people touch their face alot.
This might not answer what you were looking for but the other answer covered it pretty well so I thought I'd give you another angle to the question!
Hope this helps!!
pls help as soon I will give brainlist
Answer:
1) Conditions necessary for rusting are:
a) Presence of atmospheric oxygen or air
b)Presence of water or moisture
2) For protecting the iron gate, we can paint it because the paint will coat it and protect it from atmospheric oxygen and water.
3) Magnesium, Carbon and Oxygen (MgCO₃)
Can someone please help me with this question
Answer:
the second one I think...
Answer:
The answer is the first one.
Acceleration is the change of velocity
Velocity is another term for speed with direction.
In the following reaction, which are the products?
Mg + 2HCl —> H2 + MgCl2
If you could, please explain as well.
Answer: H2 + MgCl2
Explanation: As they are on the right side of the equation/ are the products being made as a result of the reaction, they are the products.
In which orbitals would the valence electrons for carbon (C) be placed?
Answer: orbitals supernumerary
Explanation:
Answer:
both S orbital and p orbitals
Explanation:
took the exam got the question right.
What is the definition of a scientific theory
A) A method of learning that emphasizes reason as the way to understand the world.
B) A brief statement that summarizes past observations and predicts future ones.
C) A model that explains the underlying reasons for observations and laws.
D) The equivalent of a scientific opinion which others may disagree with.
E) None of these.
Answer:
The correct answer to the following question will be Option C.
Explanation:
The theory seems to be the context within which findings are explained as well as possible predictions are made. This theoretical perspective discusses the factors behind the results as well as the laws.Theories have been used in scientific knowledge to give wide interpretations to accommodate observed facts in case the root reason is still yet to be found as well as characterized.So that Option C will be the right answer.
What is the frequency of radiation emitted by a photon of light if the energy released during its transition to ground state is 3.611 × 10-15 joules? (Planck's constant is 6.626 × 10-34 joule seconds)
Answer:
5.449 x 10¹⁸ Hz
Explanation:
Energy (E) =Frequency (F) x Plancks constant (h)
F= 3.611x10⁻¹⁵J / 6.626 x 10⁻³⁴ Js⁻¹
F =5.449 x10¹⁸ s⁻¹ or 5.449 x 10¹⁸ Hz
at what temperature would 2.10moles of N2 gas have a pressure of 1.25atm and fill a 25.0 L tank
Answer:
[tex]\large \boxed{\text{-92 $^{\circ}$C}}[/tex]
Explanation:
We can use the Ideal Gas Law and solve for T.
pV = nRT
Data
p = 1.25 atm
V = 25.0 L
n = 2.10 mol
R = 0.082 06 L·atm·K⁻¹mol⁻¹
Calculations
1. Temperature in kelvins
[tex]\begin{array} {rcl}pV & = & nRT\\\text{1.25 atm} \times \text{25.0 L} & = & \rm\text{2.10 mol} \times 0.08206 \text{ L}\cdot\text{atm}\cdot\text{K}^{-1}\text{mol}^{-1} \times T\\31.25&=&0.09847T\text{ K}^{-1}\\T& = &\dfrac{31.25}{\text{0.098 47 K}^{-1}}\\\\& = &\text{181 K}\end{array}[/tex]
2. Temperature in degrees Celsius
[tex]\begin{array} {rcl}T & = & (181 - 273.15) \, ^{\circ}\text{C}\\& = & -92 \, ^{\circ}\text{C}\\\end{array}\\\text{The temperature of the gas is $\large \boxed{\mathbf{-92 \, ^{\circ}}\textbf{C}}$}[/tex]
The diagram shows the setup of an experiment. The observations of the experiment are listed in the table below the diagram. A beaker filled three-fourths with a liquid labeled colorless silver nitrate solution is shown. A small strip is shown inside the beaker. The strip is labeled copper strip. The title of the image is Experimental Setup. Experimental Observations Observation Description 1 Copper strip became thinner 2 Gray particles were deposited on the edge of the strip Which of the following is the correct explanation for one of the given observations? (4 points) Observation 2 is a result of nitrate ions moving into the solution. Observation 2 is a result of silver ions moving into the solution. Observation 1 is a result of copper atoms losing two electrons. Observation 1 is a result of silver atoms losing one electron.
Answer:
The answer is Observation 1 is a result of copper atoms losing two electrons.
Explanation:
The electrons result in the color change of the copper strip, causing the gray particles to join onto the metal.
Answer:
C
Explanation:
Observation 1 is a result of the copper atoms losing two electrons. It came out as the right answer.
What would the molecular formula be if lithium and sulfur reacted to form a neutral compound?
Answer:
Li2SExplanation:
Since Lithium gives away one electron, I believe it goes to Sulfur.
Hope this helps! :)
Answer:
Li*2S
Explanation:
ed tell chem
Attempt 1 of 1
Which of the following is most likely to have a crystalline structure?
wood
rubber
glass
quartz
Answer: Quartz
Explanation: I looked it up ;)
the wavelength of a light wave whose frequency 5.0x 10^9 s^-1 is
Answer:
wavelength = 6 cm .
Explanation:
frequency given = 5 x 10⁹ .
wavelength = velocity of light / frequency
= 3 x 10⁸ / 5 x 10⁹
= .06 m
= 6 cm
A 500ml bottle contains 2.50 moles of gas. What is the new volume when the number of miles is increased 5.00 moles?
Answer:
The new volume is 1,000ml
Explanation:
Mathematically, we know that the number of moles per ml(volume) should be constant irrespective of the increase.
Initially, we have a volume of 500 ml and number of moles of 2.5 moles
The ratio of the number of moles to the volume is 2.5/500 = 0.005 mole/ml
Now, this is expected to remain the same even if we have an increment.
let’s call the new volume x
0.005 mol/ml = 5 moles/x ml
x = 5/0.005 = 1,000 ml
Which phrase describes a feature of a Mercator projection? is least commonly used sizes most features to scale presents longitude lines as parallel shows most accurately near the prime meridian
QUICK
Answer:
presents longitude lines as parallel
Explanation:
The Mercator projection shows longitude lines as parallel, hence greatly distorts sizes and distances near the poles. A useful feature is that a course of constant bearing shows as a straight line.
Answer:
C.) presents longitude lines as parallel
Explanation:
Took it on E2020
Which process occurs at each link in a food chain?
Some Energy is released into the environment as heat
Explanation:
NEED HELP
What is the temperature in kelvin of a gas if it is allowed to expand from 1.50 L to 4.50 L? The initial temperature is 10.0°C and pressure is constant throughout the change. Which equation should you use?
Answer:
Explanation:
V1/T1 =V2/T2 at constnant pressure
Answer:
c
Explanation:
