<span>100.
ppb of chcl3 in drinking water means 100 g of CHCl3 in 1,000,0000,000 g of water
Molarity, M
M = number of moles of solute / volume of solution in liters
number of moles of solute = mass of CHCl3 / molar mass of CHCl3
molar mass of CHCl3 = 119.37 g/mol
number of moles of solute = 100 g / 119.37 g/mol = 0.838 mol
using density of water = 1 g/ ml => 1,000,000,000 g = 1,000,000 liters
M = 0.838 / 1,000,000 = 8.38 * 10^ - 7 M <----- answer
Molality, m
m = number of moles of solute / kg of solvent
number of moles of solute = 0.838
kg of solvent = kg of water = 1,000,000 kg
m = 0.838 moles / 1,000,000 kg = 8.38 * 10^ - 7 m <----- answer
mole fraction of solute, X solute
X solute = number of moles of solute / number of moles of solution
number of moles of solute = 0.838
number of moles of solution = number of moles of solute + number of moles of solvent
number of moles of solvent = mass of water / molar mass of water = 1,000,000,000 g / 18.01528 g/mol = 55,508,435 moles
number of moles of solution = 0.838 moles + 55,508,435 moles = 55,508,436 moles
X solute = 0.838 / 55,508,435 = 1.51 * 10 ^ - 8 <------ answer
mass percent, %
% = (mass of solute / mass of solution) * 100 = (100g / 1,000,000,100 g) * 100 =
% = 10 ^ - 6 % <------- answer
</span>
Answer:
173.5 g
Explanation:
This question seems incomplete, as the power by which 10 is increased is missing. I will answer this question assuming the given number of molecules is <em>7.03x10²³ </em>molecules. A different number of molecules will give a different answer, but the procedure remains the same.
First we <u>convert the given number of molecules into moles</u>, using <em>Avogadro's number</em>:
- 7.03x10²³ molecules ÷ 6.023x10²³ molecules/mol = 1.17 mol
Then we <u>convert magnesium nitrate moles into grams</u>, using its <em>molar mass</em>:
- 1.17 mol * 148.3 g/mol = 173.5 g
<span>d. 418 mmHg
The ideal gas law is
PV = nRT
where
P = Pressure
V = Volume
n = number of moles
R = Ideal gas constant (62.363577 L Torr/(K*mol) )
T = Absolute temperature
We are going to first need to calculate how many moles of gas particles we have, so solve for n
PV = nRT
PV/RT = n
Now we need to calculate what values to plug into the formula. mmHg is equal to torr for 6 significant figures, so we'll use that unchanged. 39.3C needs to be converted to Kelvin by adding 273.15, giving 312.45, and now to plug in the values and calculate.
(882.7 Torr)(17.2 L)/((62.363577 L Torr/(K*mol)) 312.45K) = n
(15182.44 Torr*L)/( 19485.49963 L Torr/mol ) = n
0.779166061 mol = n
So we now know that we have 0.779166061 moles of gas particles. The average molar mass of the gas particles will be the mass of the gas divided by the moles of particles. So:
28.3 g / 0.779166061 mol = 36.32088384 g/mol
Now we need to solve this equation:
x*Mo + (1-x)*Ma = A
where
x = percentage of the gas that's oxygen
Mo = Molar mass of oxygen gas
Ma = Molar mass of argon gas
A = average molar mass of unknown gas
Let's solve for x:
x*Mo + (1-x)*Ma = A
x*Mo + Ma - xMa = A
x*Mo - xMa = A - Ma
x(Mo - Ma) = A - Ma
x = (A - Ma)/(Mo - Ma)
Now let's calculate the molar mass of argon and oxygen to determine the percentage of oxygen.
Atomic weight argon = 39.948
Atomic weight oxygen = 15.999
Molar mass oxygen = 2*15.999 = 31.998 g/mol
And plug in the numbers we have to get x.
x = (A - Ma)/(Mo - Ma)
x = (36.32088384 - 39.948)/(31.998 - 39.948)
x = -3.62711616 / -7.95
x = 0.456241026
So 45.62% of gas is oxygen. And the partial pressure of oxygen will be 45.62% of 882.7 mmHg = 403 mmHg
The value of 403 mmHg does not match any of the available choices. The most likely cause for the discrepancy is the use of lower precision constants. For instance, the ideal gas constant I used was selected from a table of available choices expressed in different units. I chose the value that most closely matches the units available in the problem of 62.363577 L Torr/(K*mol) instead of the more common 8.3144598 L*kPa/(K*mol) value so I wouldn't need to convert from mmHg to kPa. Looking closely at the data, I suspect a problem with the original problem. If the temperature is off by as little as 1.2 degrees (perhaps by accidentally using 272 K instead of 273.15 K as the conversion offset), the calculated answer would be 418 mmHg. In any case, option d. 418 mmHg is the closest available choice with an error of less than 4%. All the other options have errors exceeding 8%.</span>
Answer:
Both are endothermic reactions.
Explanation:
Chemical equation:
1/2H₂(g) + 1/2I₂(g) → HI(g) + 6.2 kcal/mol
Chemical equation:
21.0 kcal/mol + C(s) + 2S(s) → CS₂
Both reaction are endothermic because heat is added in both of reactions.
Endothermic reactions:
The type of reactions in which energy is absorbed are called endothermic reactions.
In this type of reaction energy needed to break the bond are higher than the energy released during bond formation.
For example:
C + H₂O → CO + H₂
ΔH = +131 kj/mol
it can be written as,
C + H₂O + 131 kj/mol → CO + H₂
Exothermic reaction:
The type of reactions in which energy is released are called exothermic reactions.
In this type of reaction energy needed to break the bonds are less than the energy released during the bond formation.
For example:
Chemical equation:
C + O₂ → CO₂
ΔH = -393 Kj/mol
it can be written as,
C + O₂ → CO₂ + 393 Kj/mol