# Homework Help: Kinetic energy and heat

1. Nov 23, 2007

### jesusismagic28

Help on a few homework problems?

1). Use the bond dissociation energies in Table 7.1 to calculate an approximate H° for the industrial synthesis of isopropyl alcohol (rubbing alcohol) by reaction of water with propene.
I'm given: CH3CH=CH2+H2O -> CH3CHCH3 [with an OH bond coming from the second carbon atom]

2). Assume that the kinetic energy of a 2300 kg car moving at 115 km/h could be converted entirely into heat. What amount of water could be heated from 20.°C to 45°C by the car's energy?

3). The addition of H2 to C=C double bonds is an important reaction used in the preparation of margarine from vegetable oils. If 50.0 mL of H2 and 50.0 mL of ethylene (C2H4) are allowed to react at 1.5 atm, the product ethane (C2H6) has a volume of 50.0 mL. Calculate the amount of PV work done, and tell the direction of the energy flow.
C2H4(g) + H2(g) C2H6(g)

4). Assume that a particular reaction evolves 227 kJ of heat and that 51 kJ of PV work is gained by the system. What are the values of H and E for the system? What are the values of H and E for the surroundings?

5). Instant cold packs used to treat athletic injuries contain solid NH4NO3 and a pouch of water. When the pack is squeezed, the pouch breaks and the solid dissolves, lowering the temperature because of the following endothermic reaction.
NH4NO3(s) + H2O(l) NH4NO3(aq) H = +25.7 kJ

What is the final temperature in a squeezed cold pack that contains 50.0 g of NH4NO3 dissolved in 115 mL of water? Assume a specific heat of 4.18 J/(g·°C) for the solution, an initial temperature of 25.0°C, and no heat transfer between the cold pack and the environment.

6). Calculate H°f for benzene, C6H6, from the following data.
2 C6H6(l) + 15 O2(g) 12 CO2(g) + 6 H2O(l) H° = -6534 kJ

H°f (H2O) = -285.8 kJ/mol
H°f (CO2) = -393.5 kJ/mol

Any help would be greatly appreciated. I've tried all of them several different ways and cannot figure it out.

2. Nov 24, 2007

### eli64

a few?? problems

can you show us how you tried to solve these, we can help you better if we see what you've already done - as you tried them several different ways, just give us the ones that are your best guess

- include what equations you are using