1) Consider the formation of sulfur trioxide according to the reaction:
2 SO2(g) + O2(g) -> 2 SO3(g) delta H = -198
How much heat is evolved in the formation of 750 grams of SO3?
So I did 193 X (750/2*80.0642) = 904.
The answer choices given are 10.6, 928, 1.86 X 10^3, 7.43 X 10^4, 3.71 X 10^3
Did I do this correctly?
You have a typo. The 193 is 198 in the problem so that makes the answer you should get 928 instead of 904 and 938 is one of the answers.
Technically, there is no right answer for a number of reasons. First, the -198 in the problem has no units. Is that J or kJ.? Probably kJ. Next, the answers don't have units either. I assume those are kJ also.
Yes all the units are kJ.
To determine the amount of heat evolved in the formation of 750 grams of SO3, you need to use the given enthalpy change (delta H) and the stoichiometry of the reaction.
First, let's find the molar mass of SO3:
Sulfur (S) has a molar mass of 32.06 g/mol.
Oxygen (O) has a molar mass of 16.00 g/mol.
SO3 has a molar mass of (32.06 g/mol) + (3 * 16.00 g/mol) = 80.06 g/mol.
Next, use the stoichiometry of the reaction to find the number of moles of SO3 formed from 750 grams of SO3.
The molar ratio between SO2 and SO3 in the balanced equation is 2:2 (or 1:1), meaning that for every 2 moles of SO2, 2 moles of SO3 are formed.
So, if we have 750 grams of SO3, we can calculate the number of moles:
moles of SO3 = 750 g / molar mass of SO3
moles of SO3 = 750 g / 80.06 g/mol = 9.370 mol
Now, we can determine how much heat is evolved by multiplying the number of moles of SO3 by the enthalpy change (delta H). Since the reaction indicates that 2 moles of SO3 form with a delta H of -198 kJ, we can calculate the heat evolved for 9.370 moles of SO3:
heat evolved = (delta H) * (moles of SO3)
heat evolved = -198 kJ/mol * 9.370 mol = -1857.66 kJ
Since the answer choices are given in scientific notation, let's convert the answer to scientific notation:
-1857.66 kJ = -1.85766 × 10^3 kJ
Among the answer choices provided, the closest one to -1.85766 × 10^3 kJ is 1.86 × 10^3 kJ. Therefore, the answer would be 1.86 × 10^3 kJ.
Note: It seems there is a small calculation error in your original attempt. You multiplied by 193 instead of -198 when calculating the answer.