Part A A calorimeter contains 28.0 mL of water at 13.5 C . When 2.20 g of X (a s

Question

Part A A calorimeter contains 28.0 mL of water at 13.5 C . When 2.20 g of X (a substance with a molar mass of 65.0 g/mol ) is added, it dissolves via the reaction

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

and the temperature of the solution increases to 26.0 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/(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

X(s)+H2O(l) ----> X(aq)

no of moles of X = 2.2/65 = 0.034 mole

q reased = m*s*DT

mass of solution = 28*1 + 2.2 = 30.2 grams

specificheat of solution = 4.18 j/g.c

DT = (26-13.5) = 12.5 c

= 30.2*4.18*12.5 = 1577.95 joule

= 1.578 kj

so that,

0.034 moles of X = 1.578 kj

1 mole of X = 1.578/0.034 = 46.41 kj/mol

DH = 46.41 kj/mol

Related Questions

Navigate

• Browse (All)
• Browse P
• Subjects

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