Practice Problems #28-32, #65-68

Interpreting Solubility Curves

Practice Problems #22-26

Practice Problems #1-2, #10-15

Molarity Questions

Heat of a Combustion of a Candle

Data:

Length of candle: 4 cm

Mass of candle and foil apparatus before burning:1.21g

Mass of candle and fill apparatus after burning for five minutes: .69g

Length of Candle after burning for five minutes: 1.90 cm

Analyze and Conclude Questions:

1. While the candle is burning, draw a picture of what you see.

2. Examine the flame closely. Is it the wax or the wick that burns?

 The wick burns when a candle is lit.

3. If you said the wax, how does the wax burn without touching the flame? If you said the wick, what is the function of the wax?

 The purpose of the wax is to prolong the burning of the wick and thus the length the candle burns. It        stops the entire wick from catching on fire at once.

4. If you could measure the temperature near the flame, you would find that the air is much hotter above the flame than it is beside it. Why?

  Because heat rises, so the hot air resides above the flame.

5. How much length and mass did the candle lose? Are these data more consistent with the wax or the wick burning?

  The candle lost .52g in mass, and 2.1 cm in length, and this is more consistent with the wick burning than the wax, because the wax stayed in the apparatus, and the wick burned up.

6. Keeping in mind that wick is also a verb, explain how a candle works.

  When a candle is lit, the wick catches on fire, which heats the air around the flame. This heat then melts the wax that surrounds more of the wick, revealing it. This allows the wick to burn farther down, which in turn burns more wax, in a cycle of wick burning and wax melting.

7. Formula for candle wax is C20H42. Write a balanced equation

C20H42 + O2 --> CO2 + H2O

8. Number of moles of wax burned.

C20H42 --> 282g

.5g / 282g/mol --> 0.00177mol

9. Heat of combustion of candle wax?

11656kJ

10. Amount of heat released in reaction.

20.63kJ

Heat of Fusion for Ice

Purpose:

Procedure:

1) Start with 100 ml H2O at fifty degrees Celsius

2) Place H2O into calorimeter and record temperature

3) Drop two to three ice cubes into calorimeter and stir until temperature no longer drops. Remove any remaining ice (don't run out of ice!)

4) Measure new volume

Data:

Temperature of H2O in calorimeter: 50 degrees Celsius

Volume of H2O after melting ice cubes: 163 ml

Calculations:

1) Mass of H2O used: 100 ml=100 g

2) Heat given by water: 100g x -48.7 x 4.18= -20,356.6 joules

3) Heat taken by ice: 20,356.6 joules

4) Mass of ice: 63g

5) Moles of Melted ice: 63g---> 3.5 moles

6) Heat Fusion: 20.4 kJ/3.5 mol ----> 5.8 kJ

Conclusion: