The heat of solution of one mole of Na2SO4.10H2O is -78.7 kJ, and that of dehydration, -81.6 kJ. The heat of solution (kJ) of anhydrous sodium sulphate is

Question

The heat of solution of one mole of Na2SO4.10H2O is -78.7 kJ, and that of dehydration, -81.6 kJ. The heat of solution (kJ) of anhydrous sodium sulphate is (A) +2.9 kJ (B) +160.3 kJ (C) -2.9 kJ (D) -160.3 kJ

Tardigrade Admin · Accepted Answer

<img class="img-fluid question-image" alt="Solution" src="https://cdn.tardigrade.in/q/nta/c-ctz7wyulpsiyplam.jpg" /> From Hess's law, textQ = - (- 81.6 textkJ) + (- 78.7 textkJ) = 81.6 textkJ - 78.7 textkJ = + 2.9 textkJ

Q. The heat of solution of one mole of $N a_{2} S O_{4} .10 H_{2} O$ is -78.7 kJ, and that of dehydration, -81.6 kJ. The heat of solution (kJ) of anhydrous sodium sulphate is

+2.9 kJ

+160.3 kJ

-2.9 kJ

-160.3 kJ

From Hess's law, $Q = - (- 81.6 kJ) + (- 78.7 kJ)$
$= 81.6 kJ - 78.7 kJ = + 2.9 kJ$

Q. The heat of solution of one mole of Na2​SO4​.10H2​O is -78.7 kJ, and that of dehydration, -81.6 kJ. The heat of solution (kJ) of anhydrous sodium sulphate is