Answer to Question #136643 in General Chemistry for Audra

Question

A 1.92 g sample of a soluble salt dissolves in 22.9 mL of water in a coffee cup calorimeter. When the salt dissolves the temperature in the calorimeter decreases by 11.6 °C. What is the energy per gram (J/g) for the dissolution of the salt?

Assume the specific heat of the solution is the same as water; 4.184 J/g°C, that the density of water is 1.00 g/mL, and that the calorimeter itself does not absorb or release any heat.

Answer 1

Water

$Mass=22.9ml\newline Specific\ heat\ capacity=4.184J/g^0C\newline \Delta T=11.6°C$

Soluble salt

$Mass=1.92 g$

Heat lose of water is the same as heat lose of solution since there

is no heat exchange.

$(\Delta H)_{sol}\ or (q)= ms\Delta T$

$m= mass\ of\ solution \newline m=22.9+1.92=24.82g \newline s=4.184J/g°C\newline \Delta T=-11.6°C\ since\ it's\ a\ decrease$

Plugging in the values into the formula;

$q= 24.82*4.184*-11.6\newline q=-1204.6J$

For one mole of the salt

$-1204.6÷1= -1204.6J/g$