A student is determining the enthalpy of solution for ammonium nitrate by addingammonium nitrate to a calorimeter and measuring the temperature change.The accepted value is ΔHsol’n = 25.7 kJ/mol.A student, not paying attention, adds 1.5g of ammonium nitrate instead of 1.0g.When they perform their calculations, they use 1.0g as the mass.Will their calculation result in an answer that is higher than the accepted value orlower? Explain. (2 marks)
Question
A student is determining the enthalpy of solution for ammonium nitrate by addingammonium nitrate to a calorimeter and measuring the temperature change.The accepted value is ΔHsol’n = 25.7 kJ/mol.A student, not paying attention, adds 1.5g of ammonium nitrate instead of 1.0g.When they perform their calculations, they use 1.0g as the mass.Will their calculation result in an answer that is higher than the accepted value orlower? Explain. (2 marks)
Solution
The student's calculation will result in an answer that is lower than the accepted value. This is because the student used more ammonium nitrate (1.5g instead of 1.0g) but calculated as if they only used 1.0g. This means they are dividing the heat change by a larger amount of substance than they actually used, which will result in a smaller enthalpy change per mole. Therefore, their calculated ΔHsol’n will be lower than the accepted value of 25.7 kJ/mol.
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