1) A) a calorimeter contains 33.0mL of water at 13.0 Celcius. when 2.50 g of X (

Question

1)

A) a calorimeter contains 33.0mL of water at 13.0 Celcius. when 2.50 g of X ( a substance with a molar mass of 82.0g/mol) is added, it dissolves via the reaction

                                                                      X(s)+H2O(L)--->X(aq)

and the temperature of the solution increases to 26.5 Celcius. Calculate the enthalpy change, DELTA H, for this reaction per mole of X

Assume that the specific heat of the resulting solution is equal to that of water [4.18 J/(g * C)], that density of water is 1.00 g/mL and that no heat is lost to the calorimeter itself, nor to the surroundings. Express the change in enthalpy in kilojoules per mole to three significant figues

B) Consider the reaction

C12H22O11(s) + 12O2(g)--->12CO2(g)+11H2O(l)

in which 10.0 g of sucrose, C12H22O11, was burned in a bomb calorimeter with a heat capacity of 7.50 kJ/ Celcious. The temperature increase inside the calorimeter was found to be 22.0 Celcius. Calculate the change in internal energy, Delta E, for this reaction per mole of sucrose.

Express the change in internal energy in kilojoules per mole to three significant figures

Explanation / Answer

A)Energy released by adding X = (1g/cc)(33.0cc)(4.18J/(g*C))(26.5-13) = 1862.19J

Moles of X added = 2.50/82.0

Delta H = -1862.19 J *82.0/2.50 = -61.1kJ/mol

B)Moles of sucrose used up = 10.0/342.3

Rise in temperature = 22.0 Celsius

Heat absorbed by calorimeter = 22.0*7.5 kJ =165kJ

Delta E = -165kJ*82/2.5mol-1 = 5.412MJ/mol

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