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You need your calculator and paper to write on

You need your calculator and paper to write on

You will need the chart on page 2 for one of the problems.

How many joules of energy is required to change 50mL of liquid water at 85ºC to steam at 115ºC?

Some helpful information:

ΔHvap(water) = 40.7 kJ/mol

ΔHfus(water) = 6.01 kJ/mol

Freezing temperature of water = 0.06ºC

Boiling temperature of water = 99.4ºC

Answer: 117,000

Approx 7 minutes

An 8.50-gram sample of an unknown metal at 118ºC is placed into a coffee-cup calorimeter containing 35.0 mL of water. The water’s temperature increased from 35.000ºC to 36.793ºC. What is the identity of the metal? [You will need to use your packet chart.]

Answer: Brass

Approx 7 minutes

A 3-gram sample of heptane, C7H16, is combusted with 1,050 mL of oxygen gas at STP.

ΔH = - 4819 J/mol rxn.

- Write the balanced reaction.
- How much energy will be produced?
- The energy is used to heat 90 grams of water originally at 17°C. What is the final temperature of the water?
Answers:

2) -20.5 J

3) 17.05°C

When you finish, get your packet out and work some extra problems!!! No sitting around!

Approx 15 minutes