1. Which of the following reactions absorbs heat from the surroundings in order

ID: 792053 • Letter: 1

Question

1. Which of the following reactions absorbs heat from the surroundings in order to proceed to completion?

I. CO (g) +1/2 O2 (g) ----> CO2 (g)

II. Al2O3 (s)-----> 2Al (s) + 3/2 O2 (g)

III. SO3 (g) + 99.2 kj----> S (s) + 3/2 O2 (g)

DELTA H: -283.0KJ ENDOTHERMIC

A. I ONLY

B.I and III

C.I and II

D.II and III

E. All of them

2. What amount of heat is given off when burning 8.0 g of C2H2 (g) in excess O2 (g) show work please

2C2H2 (g)+ 5 O2 (g) ----> 4 CO2 (g)+2H2O(L) delta h= -2600kj

A. -200kj

B.-400kj

C.-800kj

D.-1600kj

E. None of these

Decomposition reactions are endothermic reactions in general, since heat energy is required to break the bonds.

Thus reactions of decomposition of SO3 and Al2O3 are endothermic reactions i.e. reactions 2 and 3. Hence the answer is option (D).

2) 2 moles of C2H2 i.e (2 * 26) = 52g of C2H2 requires 2600 kJ of heat.

then, 8.0 g would require (8*2600)/52 = 400 kJ of heat.

Hence answer is option (B).

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