2.500 grams of metal X (molar mass = 65.39 g/mole) was reacted with 100.0 mL of

Question

2.500 grams of metal X (molar mass = 65.39 g/mole) was reacted with 100.0 mL of a 1.500 M HCL solution in a coffee cup calorimeter. The temperature went from 12.50 C to 40.50 C. Determine the reaction enthalpy per mole of metal X. The specific heat of the solution is 4.184 J/g C. Assume a solution density 1.00 g/mL and a perfect system.

and

20.12 grams of butane, C4H10 , was combustedwith oxygen in a bomb calorimeter. The temperature of 0.500kilograms of water went from 5.00 C to 25.89 C. The specific heatof the water is 4.184 J/g C. Assume a solution density of 1.00g/mL. Determine the heat (kJ) evolved per mole of butane. Assume aperfect bomb calorimeter.

Explanation / Answer

Mass of X = 2.5 g

Mass HCl = density x volume =100 ml x1 g / ml = 100g

So, total Mass of system = 100+2.5 = 102.5 g

change in temp = 40.5oC - 12.5oC = 28oC

Q = m Cp x delta T

Q = 102.5 x 4.184 x 28oC = 12008.08J

Now, no. of moles of X present = mass taken/molar mass = 2.5/65.39 = 0.038 moles

Heat of reaction per mole of X = 12008.08J/0.038 moles = 316002.1J/mole = 316 kJ/mol

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