Part A A calorimeter contains 29.0 mL of water at 12.5 C . When 1.70 g of X (a s

Question

Part A A calorimeter contains 29.0 mL of water at 12.5 C . When 1.70 g of X (a substance with a molar mass of 54.0 g/mol ) is added, it dissolves via the reaction X(s)+H2O(l)X(aq) and the temperature of the solution increases to 26.5 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/(gC)], 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 figures.

Explanation / Answer

Given that the density of water= 1.00 g/mL

Density = mass/ volume

Mass= density * volume

= 29.0 ml*1.00 g/ ml

= 29.0 g

Mass of solution = mass of water + mass of solute

= 29.0 g+ 1.70 g

= 30.7 g

Amount of heat = m*c* dT

= 30.7 g*4.18 J/(gC * {26.5 C -12.5 C}

= 1796.564 J

=1.78 KJ

Now calculate the enthalpy in kilojoules per mole; First we calculate eth mole of solute:

1.70 g of X /54.0 g/mol

= 0.0315 moles

the enthalpy in kilojoules per mole = 1.78 KJ /0.0315 moles

= 56.5 KJ/ mole

Related Questions

Navigate

• Browse (All)
• Browse P
• Subjects

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