Which reaction shows that the enthalpy of formation of CS2 is Hf = 89.4 kJ/mol?
A. C(s) + 2S(s) CS2(l) + 89.4 kJ
B. C(s) + 2S(s) + 89.4 kJ CS2(l)
C. C(s) + 2S(s) + 89.4 kJ CS2(l) + 89.4 kJ
D. C(s) + 2S(s) CS2(l)
I think the answer is a or b
its b
Well, I hate to break it to you, but your thinking is off. The correct answer is actually D. C(s) + 2S(s) CS2(l). The enthalpy of formation, Hf, refers to the energy change when one mole of a compound is formed from its elements in their standard states. In this case, the enthalpy of formation of CS2 is given as 89.4 kJ/mol, but there is no need to include it in the balanced equation. So, no need for any extra kJ/mol in the equation, just the simple formation of CS2. Keep those chemistry skills rolling!
To determine the reaction that shows the enthalpy of formation (ΔHf) of CS2 as 89.4 kJ/mol, we need to understand what enthalpy of formation means.
The enthalpy of formation (ΔHf) is the change in enthalpy when one mole of a substance is formed from its constituent elements in their standard states.
In this case, CS2 is being formed from its constituent elements, which are carbon (C) and sulfur (S). Therefore, we need a reaction that includes the elements C and S in their standard states, and CS2 as the product, with ΔHf equal to 89.4 kJ/mol.
Let's analyze the given options:
A. C(s) + 2S(s) → CS2(l) + 89.4 kJ
This reaction shows the formation of CS2, but it includes the addition of 89.4 kJ of energy. The ΔHf value should be included on the product side, but this reaction includes it on the reactant side, so this is not the correct option.
B. C(s) + 2S(s) + 89.4 kJ → CS2(l)
This reaction includes the addition of 89.4 kJ of energy as a reactant. Since the ΔHf value should be included on the product side, this is not the correct option.
C. C(s) + 2S(s) + 89.4 kJ → CS2(l) + 89.4 kJ
This reaction is the same as option B, where 89.4 kJ is included as a reactant, and another 89.4 kJ is included as a product. Again, the ΔHf value should be included on the product side. Therefore, this is not the correct option.
D. C(s) + 2S(s) → CS2(l)
This reaction represents the formation of CS2 from its constituent elements (C and S) without any additional energy included. This is the correct option.
Therefore, the correct answer is D. C(s) + 2S(s) → CS2(l).
so whats the answer???
Why not add arrows for clarity? That's what they're for. Have I put them in at the right place? Only the author knows.
A. C(s) + 2S(s)==> CS2(l) + 89.4 kJ
B. C(s) + 2S(s) + 89.4 kJ ==>CS2(l)
C. C(s) + 2S(s) + 89.4 kJ ==> CS2(l) + 89.4 kJ
D. C(s) + 2S(s) ==> CS2(l)
It can't be A because that shows 89.4 kJ heat RELEASED and dH is + 89.4. For heat to be released dH must be -.
B shows it uses heat and is endothermic which is + 89.4
C. You NEVER see dH on BOTH sides of the same equation.
D. It can't be D because it has no dH at all.