8. Thermochemistry

Constant-Pressure Calorimetry

Multiple Choice
Using a coffee-cup calorimeter, the ΔH_rxn for the dissolution of KCl(s) into KCl(aq) is determined. The initial temperature of the water in the calorimeter is 26.5°C. After the reaction, the temperature is measured again and found to be 23.0°C. What is the sign of ΔH_rxn for this reaction?
Multiple Choice
When gasoline is burned at constant pressure, a certain amount of heat is emitted and work is done. Which of the following must be true?
Multiple Choice
A 115.6 g piece of copper metal at 182.5 ºC is placed into 120.0 mL of methylene chloride at 31.0 ºC within a coffee-cup calorimeter. If the final temperature of the solution is 50.3 ºC, what is the specific heat of methylene chloride? Assume the calorimeter absorbs a negligible amount of heat. The specific heat of copper is 4.184 J/g ∙ ºC and the density of methylene chloride is 1.33 g/cm³.
Multiple Choice
You place 75.0 mL of 0.100 M NaOH in a calorimeter at 25.00 ºC and carefully add 55.0 mL of 0.200 M HNO₃, also at 25.00 ºC. After stirring, the final temperature is 53.35 ºC. Calculate the enthalpy ∆H_rxn (in J/mol) for the formation of water. (Specific heat capacity, Cs, and density of the solution:4.184 J/g∙K and 1.00 g/mL).
Open Question
When a 4.25g sample of solid ammonium
Multiple Choice
A coffee-cup calorimeter contains 130.0 g of water at 25.2 °C. A 124.0-g block of copper metal is heated to 100.4 °C by putting it in a beaker of boiling water. The specific heat of Cu(s) is 0.385 J/g·K. The Cu is added to the calorimeter, and after thermal equilibrium is reached, the final temperature of the system is measured. What is the final temperature of the water in the calorimeter?
Multiple Choice
In a constant-pressure calorimetry experiment, butane was burnt causing a temperature change of 25.5 K in 1200 g of water (specific heat capacity = 4.18 J/g⋅K). Calculate the heat change of the water. Give the answer to three significant figures.
Multiple Choice
In a coffee-cup calorimeter experiment, 10.00 g of a soluble ionic compound was added to the calorimeter containing 75.0 g H2O initially at 23.2°C. The final temperature of the solution was 31.8°C. What was the change in enthalpy (ΔH) for the dissolution of the compound?
Multiple Choice
In a constant-pressure calorimeter, 70.0 mL of 0.330 M Ba(OH)2 is mixed with 70.0 mL of 0.660 M HCl, causing the temperature to rise from 22.99 °C to 27.49 °C. Assuming the solution has the same density and specific heat as water, what is the enthalpy change (ΔH) of the reaction per mole of Ba(OH)2?
Multiple Choice
In a constant-pressure calorimetry experiment, a coffee-cup calorimeter containing 100 mL of water is used. The initial temperature of the calorimeter is 23.0 °C. If 8.20 g of CaCl2 is added to the calorimeter, what will be the final temperature of the solution, given that the enthalpy change for the dissolution of CaCl2 is -82.8 kJ/mol?
Multiple Choice
In a constant-pressure calorimetry experiment, a coffee-cup calorimeter containing 100 mL of water at an initial temperature of 23.0 °C is used. If 4.60 g of CaCl2 is added to the calorimeter, what will be the final temperature of the solution, assuming the dissolution of CaCl2 is an exothermic process?
Multiple Choice
You are experimentally determining the change in enthalpy when dissolving an ionic compound in water using a coffee-cup calorimeter. When you dissolve 38.28 g of the ionic compound (molar mass = 102 g/mol) in 369 g of water in a coffee-cup calorimeter, the temperature of the solution changes from 25.0°C to 28.5°C. Given that the specific heat capacity of water is 4.18 J/g°C, what is the change in enthalpy (ΔH) for the dissolution process?
Multiple Choice
What is the enthalpy change (ΔH) for the reaction when 200.0 mL of 0.100 M AgNO3 is mixed with 100.0 mL of 0.100 M NaCl in a coffee cup calorimeter, given that the temperature rises from 24.69°C to 25.16°C and the calorimeter has a heat capacity of 105.5 J/°C?
Multiple Choice
When 1.80 g of magnesium metal reacts with 200 mL of 6.00 M aqueous HCl, the temperature rises from 25.0 °C to 42.1 °C. Calculate ΔH in kilojoules for the reaction, assuming the heat capacity of the calorimeter is 776 J/°C. What is the value of ΔH?