Dropbox: Heat Energy Assessment

Answer the questions on heat energy listed below. Please note that you must include units throughout all of your calculations and provide your answer in scientific notation to the correct number of significant digits.

Click on the red flags to the left to review content on scientific notation and significant digits.

1. What mass of methane (CH_4(g)) needs to be burned to heat 300 mL of water from 23.0 ^oC to the boiling point (98.0 ^oC)? (ΔH_combustion = -639 kJ/mol; specific heat of water = 4.18 J/g^oC)
2. A sample of methanol (CH₃OH_(aq)), with a specific heat of 2.51 J/g^oC needed 27.1 kJ of energy to heat it from 22.0 ^oC to 52.0 ^oC. What is the mass of methanol used?
3. 6.40 kJ of energy is needed to raise the temperature of a calorimeter and its contents 1.00 ^oC. When 2.00 g of propyne (C₃H_4(g)) is burned in a calorimeter, the temperature of the calorimeter was raised 15.0 ^oC. What is the molar heat of combustion of propyne?
4. 250 mL of water is heated from 3 ^oC to 90 ^oC on a butane stove. Assume all the heat from combustion is used to warm the water.

C₄H_10(g) + 13/2 O_2(g) → 4 CO_2(g) + 5 H₂O_(l)

Standard Enthalpies of Formation (ΔH^o_f):

• C₄H_10(g) = -124.8 kJ/mol
• CO_2(g) = -393.5 kJ/mol
• H₂O_(l) = -285.8 kJ/mol

1. What is the total amount of heat required for the process?
2. What is the molar heat of combustion for butane?
3. What is the mass of butane needed for this process?