Lesson Worksheet: Using Calorimetry Measurements Chemistry • 10th Grade

In this worksheet, we will practice using the specific heat of a material to calculate the mass, temperature change, or amount of heat exchanged.

Q1:

The enthalpy change when calcium chloride (CaCl)2 dissolves in water is 82.9 kJ/mol. The heat capacity of the solution is approximately equal to that of water (𝑐=4.18/)JgK. If 90 g of CaCl2 dissolves in 5.0 L of water at 20C, what is the temperature of the resulting solution?

Q2:

The melting enthalpy of ice is 6.01 kJ/mol. At 0.00C, combustion of 10.0 g of butane (CH)410 releases sufficient heat to melt 1.20 kg of ice and increase the temperature of the resulting water (𝑐 = 4.184 J/g⋅K) to 18.9C. What is the enthalpy of combustion of butane?

  • A2.9×10 kJ/mol
  • B5.5×10 kJ/mol
  • C2.4×10 kJ/mol
  • D1.3×10 kJ/mol
  • E2.3×10 kJ/mol

Q3:

Aqueous iron(II) chloride (FeCl)2 and hydrogen peroxide (HO)22 react in excess dilute hydrochloric acid according to the following equation: FeCl()+12HO()+HCl()FeCl()+HO()22232aqaqaqaql The enthalpy change for this reaction is 149 kJ/mol. At 20.0C, solutions containing 1.901 g of FeCl2 and 0.260 g of HO22 in 1 M aqueous HCl are mixed in an insulated container. The final solution has a volume of 100 cm3, a density of 1.000 g/cm3, and a specific heat of 4.184 J/g⋅K. Calculate, to 1 decimal place, the temperature of the solution at the end of the reaction.

Q4:

Natural gas is mostly methane. Burning natural gas in air is a highly efficient way of generating heat.

Methane combusts completely in air according to the following equation: CH+2OCO+HO4222 The combustion of 10.0 mmol of methane and excess oxygen heats a small amount of water in a bomb calorimeter by 21.1C. The water has a mass of 100 g and specific heat of 4.184/JgC. Assuming the water absorbs all heat generated by the reaction, calculate the molar enthalpy of combustion of methane.

Q5:

Aqueous sodium periodate (NaIO)4 reacts with aqueous hydroiodic acid (HI) according to the following equation: NaIO()+2HI()NaIO()+I()+HO()4322aqaqaqaql

The enthalpy change for this reaction is 493 kJ/mol and the enthalpy of solution for NaIO4 is 55.2 kJ/mol. At 20.0C, 1.85 g of NaIO4 is dissolved in 150 cm3 of 0.100 M aqueous HI in an insulated container. It is assumed that the solution has a density of 1.00 g/cm3 and a specific heat of 4.184 J/g⋅K and that the mass of solute is negligible. By identifying the limiting reagent and determining the total heat absorbed or released by the solution, calculate the temperature of the solution at the end of the reaction to 1 decimal place.

Q6:

Ethanol can be used as a fuel, either as an additive to gasoline or in pure form. Complete combustion of 50.0 mL of ethanol releases 906 kJ of heat under standard conditions. Given that the density of ethanol is 0.789 g/mL, what is the standard molar enthalpy of combustion of ethanol?

Q7:

Aqueous sodium hydroxide (NaOH) and hydrochloric acid (HCl) react according to the equation: NaOH()+HCl()NaCl()+HO()aqaqaql2 At 20.00C, 4.00 g of NaOH in 100 cm3 of water is added to 100 cm3 of 1.50 M aqueous HCl. The temperature of the resulting solution is 26.87C.

What is the enthalpy change for this reaction? Assume, for all solutions, that the heat capacity is 4.184 J/g⋅K and the density is 1.00 g/cm3.

Q8:

Aqueous sodium hydroxide (NaOH) reacts with aqueous phosphoric acid (HPO)34 according to the following equation: NaOH()+13HPO()13NaPO()+3HO()aqaqaql34342 The enthalpy change for this reaction is 52.0 kJ/mol. When 1.52 g of solid NaOH is dissolved in 300 cm3 of 0.100 M aqueous HPO34, the temperature of the solution changes from 20.00C to 22.60C. The solution has a density of 1.00 g/cm3 and specific heat of 4.184 J/g⋅K and absorbs all heat generated by the reaction. What is the enthalpy of solution for NaOH to 2 significant figures?

Q9:

An insulated cup contains 100 mL of water at 0C. When this water is warmed, its density and specific heat remain approximately constant. Which of the following, if poured into the cup, would increase the temperature of its contents by the largest amount?

  • A5 mL of water at 100C
  • B20 mL of water at 60C
  • C10 mL of water at 80C
  • D80 mL of water at 20C
  • E40 mL of water at 40C

Q10:

An insulating bucket contains 3.00 kg of sand (𝑐=0.92/)JgC mixed with 900 g of water (𝑐=4.18/)JgC. The mixture cools uniformly by 12.0C overnight. To 2 significant figures, how much heat has been released by the mixture?

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