Which Statements Are True for the Given Thermochemical Equation?

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The discussion revolves around the thermochemical equation for the reaction of hydrogen and oxygen to form water vapor, with a ΔH of -486.6 kJ. Participants analyze the validity of several statements regarding the reaction, concluding that statements A, B, and C are incorrect, while D is considered correct under constant volume conditions. However, there is confusion regarding statement E, which claims that ΔH for four moles of hydrogen and two moles of oxygen is -483.6 kJ, deemed incorrect due to a miscalculation. The thread highlights the importance of accurately interpreting thermochemical equations and the implications of reaction stoichiometry. Overall, clarity in understanding these concepts is essential for solving related problems effectively.
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1. Homework Statement

2H2(g) + O2(g) --> 2H2O(g) ΔH = −486.6kJ

Which of the following are true statements for the above chemical reaction ?

a) A phase change is involved

b) Two moles of hydrogen gas react with two moles of oxygen gas to
produce two moles of water vapor

c) Energy is absorbed by the system, the reaction species

d) If the reaction takes place at constant volume, q and ΔH must by definition have the same value

e) ΔH for reacting four moles of hydrogen gas with two moles of
of oxygen gas is −483.6 kJ

Homework Equations



None

The Attempt at a Solution



I know that A is wrong because they are all gas.
I know that B is wrong because 2 mol of Hydrogen gas react with 1 mol of Oxygen gas
I know that C is wrong because energy was released
I think that D is right because that is no work
I think that E is also right

I've tried DE, E and D
but it's wrong, please help
 
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SamTsui86 said:
a) A phase change is involved
I know that A is wrong because they are all gas.
Check.
SamTsui86 said:
b) Two moles of hydrogen gas react with two moles of oxygen gas to
produce two moles of water vapor
I know that B is wrong because 2 mol of Hydrogen gas react with 1 mol of Oxygen gas
Check.
SamTsui86 said:
c) Energy is absorbed by the system, the reaction species
I know that C is wrong because energy was released
Check.
SamTsui86 said:
d) If the reaction takes place at constant volume, q and ΔH must by definition have the same value
I think that D is right because that is no work
Check.
SamTsui86 said:
e) ΔH for reacting four moles of hydrogen gas with two moles of
of oxygen gas is −483.6 kJ
I think that E is also right
"WORNG." Four plus two is twice the energy.

SamTsui86 said:
I've tried DE, E and D
but it's wrong, please help
If "D" is "wrong," it could be a matter of limited attempts allowed, or a mistranscription.
 
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