Problem: When 0.243 g of Mg metal is combined with enough HCl to make 100 mL of solution in a constant-pressure calorimeter, the following reaction occurs:Mg(s) + 2 HCl(aq) → MgCl2(aq) + H2(g)If the temperature of the solution increases from 23.0 °C to 34.1 °C as a result of this reaction, calculate ΔH in kJ/ mol of Mg. Assume that the solution has a specific heat of 4.18 J/g°C.

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When 0.243 g of Mg metal is combined with enough HCl to make 100 mL of solution in a constant-pressure calorimeter, the following reaction occurs:

Reaction:  Mg(s) + 2 HCl(aq) → MgCl2(aq) + H2(g)


heat released by the reaction = heat absorbed by the solution

ΔH = -q


assuming volume solution = mass solution

q=mcTq=(100 g)(4.18Jg°C)(34.1°C-23.0°C)q=(100 g)(4.18Jg°C)(11.1°C)

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Problem Details

When 0.243 g of Mg metal is combined with enough HCl to make 100 mL of solution in a constant-pressure calorimeter, the following reaction occurs:

Mg(s) + 2 HCl(aq) → MgCl2(aq) + H2(g)

If the temperature of the solution increases from 23.0 °C to 34.1 °C as a result of this reaction, calculate ΔH in kJ/ mol of Mg. Assume that the solution has a specific heat of 4.18 J/g°C.

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