Exam 6: Thermochemistry

A sample of copper absorbs 43.6 kJ of heat, resulting in a temperature rise of 75.0 °C. Determine the mass (in kg)of the copper sample if the specific heat capacity of copper is 0.385 J g^-1 °C^-1.

For a particular process that is carried out at constant pressure, q = 145 kJ and w = -35 kJ. Therefore,

Calculate the initial temperature of 21.8 g of lithium (specific heat capacity = 3.582 J g^-1 °C^-1)that absorbs 1642 J of energy from the surroundings and has a final temperature of 31.08 °C.

Which of the following statements is TRUE?

The specific heat of copper is 0.385 J g^-1 K^-1. If 34.2 g of copper, initially at 21.0 °C, absorbs 4.689 kJ, what will be the final temperature of the copper?

Identify the major greenhouse gas.

The specific heat capacity of methane gas is 2.20 J g^-1 K^-1. How many joules of heat are needed to raise the temperature of 5.00 g of methane from 36.0 °C to 75.0 °C?

Calculate the initial temperature of 648 g of cucumber (specific heat capacity = 1.88 J g^-1 °C^-1)that absorbs 19857 J of heat while warming up to room temperature, 24.8 °C.

A 35.6 g sample of ethanol (C₂H₅OH)is burned in a bomb calorimeter according to the following reaction. If the temperature rose from 35.0 °C to 76.0°C and the heat capacity of the calorimeter is 23.3 kJ °C^-1, what is the value of Δ_rU°? The molar mass of ethanol is 46.07 g mol^-1. C₂H₅OH(l)+ 3O₂(g)→ 2CO₂(g)+ 3H₂O(g)Δ_rU° = ?

According to the following thermochemical equation, what mass of HF (in g)must react to produce 345 kJ of energy? Assume excess SiO₂. SiO₂(s)+ 4HF(g)→ SiF₄(g)+ 2H₂O(l)Δ_rH° = -184 kJ

Which of the following processes is endothermic?

Match the following. --w

Two solutions, initially at 24.69 °C, are mixed in a coffee cup calorimeter (C_cal = 105.5 J °C^-1). When a 200.0 mL volume of 0.100 mol L^-1 AgNO₃ solution is mixed with a 100.0 mL sample of 0.100 mol L^-1 NaCl solution, the temperature in the calorimeter rises to 25.16 °C. Determine the Δ_rH°, in units of kJ mol^-1. Assume that the density and heat capacity of the solutions is the same as that of water. Hint: Write a balanced reaction for the process.

Astatine is an extremely rare element with an estimated 28 g total on Earth. How much energy would be required to heat Earth's entire supply of astatine by 10.0 °C assuming it has a specific heat capacity similar to iodine, 0.214 J g^-1 °C^-1?

Define chemical energy.

Calculate the final temperature of a 38.1 g piece of graphitic carbon, originally at 100.0 °C, placed inside a coffee cup calorimeter containing 68.0 mL of water at 24.6 °C. The specific heat capacity of water is 4.184 J g^-1 °C^-1, the specific heat capacity of graphitic carbon is 0.709 J g^-1 °C^-1, and the density of water is 1.00 g mL^-1.

Sodium metal reacts with water to produce hydrogen gas and sodium hydroxide according to the chemical equation shown below. When 0.015 mol of Na is added to 100.00 g of water, the temperature of the resulting solution rises from 25.00 °C to 31.45 °C. If the specific heat of the solution is 4.18 J g^-1°C^-1, calculate ΔH for the reaction, as written. 2Na(s)+ 2H₂O(l)→ 2NaOH(aq)+ H₂(g)Δ_rH= ?

Calculate the work, w, gained or lost by the system when a gas expands from 15 L to 40 L against a constant external pressure of 1.5199 bar.

A 50.0 g sample of liquid water at 25.0 °C is mixed with 23.0 g of water at 89.0 °C. The final temperature of the water is ________°C.

Which of the following statements is TRUE?