University:
Cornell University
Course:
CHEM 2070 | General Chemistry I
Academic year:

2019
Views:

52

Pages:

2
Author:

acennodsrk

Image Analysis: Textual Content: Calorimetry Questions and Problems The specific heats of water and iron are 4.184 J/g°C and 0.44 J/g°C respectively. Which substance will experience a larger temperature increase upon adding 10 J? Assume each sample weighs 5 grams. (0.478°C; 4.54°C) iron b/c it has a lower specific heat. This means it takes less energy to increase in temp. 2. How much energy is required to heat 120.0 g of water from 2.0 °C to 24.0 °C? (11.05 kJ) q = 120g * (4.184 J/g°C) * (24.0°C - 2.0°C) q = 11046 J or 11.05 kJ 3. If it takes 41.72 joules to heat a piece of gold weighing 18.69 g from 10.0 °C to 27.0 °C, what is the specific heat of the gold? (0.131 J/g°C) 41.72 J = 18.69 g * c * (27.0°C - 10.0°C) c = 0.131 J/g°C 4. A certain mass of water was heated with 41,840 Joules, raising its temperature from 22.0 °C to 28.5 °C. Find the mass of water. (1538.5 g) 41840 J = m * (4.184 J/g°C) * (28.5°C - 22.0°C) m = 1538.5 g 5. The number of Joules needed to raise the temperature of 100 grams of water 10 °C is the same as the number of Joules needed to raise the temperature of 1000 grams of water (a) °C (b) 0.1 °C (c) 10 °C (d) 100 °C 6. 10.0 g of a fuel are burned under a calorimeter containing 200.0 g of H₂O. The temperature of the water increases from 15.0 °C to 55.0 °C. Calculate the total heat produced (in joules) and the heat of combustion per gram of fuel. (3347.2 J/g) 8. When solid ammonium chloride (NH₄Cl) dissolves in water, it breaks apart into aqueous ammonium ions and chloride ions. The temperature of the solution decreases by 5.0 °C. How many grams of ammonium chloride must be added to 100.0 grams of water to bring about a 5.0 °C decrease? (5.35 g) q_total = 100.0 g * (4.184 J/g°C) * (-5.0 °C) = -2092 J ΔH_soln = -2092 J / (5.35 g / 53.5 g/mol) = -20.9 kJ/mol 9. An ace chemistry student conducts an experiment to determine the ΔH for the reaction of calcium metal with HCl. Her data is summarized in the table below: mass of water in calorimeter: 123.50 g heat capacity of calorimeter: 25 J/°C initial temperature of water: 20.4 °C final temperature of water: 28.8 °C mass of Ca: 5.20 g (a) Calculate the total heat (in kJ) released by this reaction. q_total = 123.50 g * (4.184 J/g°C) * (28.8 - 20.4) + 25 J/°C * (28.8 - 20.4) q_total = 4340.5 J + 210 J = 4550.5 J or 4.55 kJ (b) Calculate the ΔH for this reaction. Report your answer in kJ/mol Ca. ΔH = -4550.5 J / (5.20 g / 40.08 g/mol) = -35 kJ/mol **10. When 80.0 grams of a certain metal at 90.0 °C was mixed with 100.0 grams of water at 30.0 °C, the final equilibrium