A calorimeter contains 22.0mL of water at 11.0?C . When 2.30g of X (a substance

Question

A calorimeter contains 22.0mL of water at 11.0?C . When 2.30g of X (a substance with a molar mass of 42.0g/mol ) is added, it dissolves via the reaction

X(s)+H2O(l)?X(aq)

and the temperature of the solution increases to 30.0?C .

Calculate the enthalpy change, ?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.

Explanation / Answer

The number of moles of the substance dissolved is 2.3/42=0.0547 mole of X

The energy produced by dissolution is

E= m*c*(tf-ti) tf and ti are final and initial temperature mass m=22g

So E = - 22*4.18*(30-11) = -1747.24 Joules (I put sign - since the system gives heat)

this for 0.0547 moles

For 1 mole -1747.24/0.0547 = -31942.2J = -31.94kJ/mole

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.