Question

1. The dimensions of the SI unit of energy, the Joule (J), are

A. K
B. kg m s C. kg m2 s-2 D. kg m-1 s-2 E. kg m2 s-1

2. Natural gas, or methane, is an important fuel. Combustion of one mole of methane releases 802.3 kilojoules of energy. How much energy does that represent in kilocalories?

A. 3.36×103 kcal B. 3.357 kcal
C. 191.8 kcal
D. 0.192 kcal

E. 1.918×105 kcal

3. What is the change in internal energy, E, (in kJ) of a system that absorbs 100 kJ of heat and does 200 kJ of work on its surroundings?

A. +100 kJ
B. -100 kJ
C. +300 kJ
D. -300 kJ
E. none of the above

4. Which ONE of the following statements is NOT true?

1. The change in enthalpy for exothermic chemical

   reactions is negative.

2. In an exothermic reaction, the reactants are lower

   in enthalpy than the products.

3. An endothermic reaction is one in which enthalpy

   is absorbed by the system from the surroundings.

4. If H° is positive in the forward direction, it will

   be negative in the reverse direction.

5. If the coefficients in a balanced reaction are multiplied by 2, the enthalpy change for the

   reaction is multiplied by 2.

5. Which one of the following is NOT an endothermic process?

A. ice melting
B. boiling soup
C. water evaporating
D. condensation of water vapor
E. dry ice subliming (evaporating without melting)

Page 1 of 3 6. The reaction shown below is ________ and therefore

heat is ________ by the reaction.
4Al(s) + 3O2(g)  2Al2O3(s); ΔHo = -3351 kJ

A. endothermic, released B. exothermic, absorbed C. endothermic, absorbed D. exothermic, released E. none of the above

Thermochemical Equations

7. When aluminum oxide, Al2O3, is heated to high temperatures, it decomposes to produce aluminum metal by the following thermochemical equation:

2Al2O3(s)  4Al(s) + 3O2(g); H° = +3352 kJ

In order to produce 75.0 g of aluminum, how much heat energy will be required?

A. 9320 kJ
B. 2330 kJ
C. 1210 kJ
D. 37300 kJ
E. none of the above

8. In the thermite reaction, powdered aluminum reacts with iron(III) oxide to produce iron metal and aluminum oxide:

2Al(s) + Fe2O3(s)  2Fe(s) + Al2O3(s); ΔH° = -852 kJ When this reaction is carried out, 1250. kJ of heat energy

are released. How many grams of iron are also formed?

A. 82.0 g
B. 2.97×104 g C. 164 g
D. 328 g
E. 9531 g

9. What is the enthalpy change (H°) for the reaction 4NaCl(s)  4Na(s) + 2Cl2(g), if the reaction 2Na(s) + Cl2(g)  2NaCl(s) has H° = -821.8 kJ?

A. +1644 kJ B. +410.9 kJ C. -1644 kJ D. -410.9 kJ E. -205.5 kJ

Answer 1

2) The dimensions of the SI unit of energy, the Joule (J), are kg masa Thus, the correct option is 'C' 2) Relationshipe used: 1 kcal = 4.184 kJ 1 kcal Energy = 802. 5 4.184 kJ = 191.8 kcal Thus, the correct option is 'C"