Question

4 grams of sodium hydroxide pellets were dissolved in $100{cm}^3$ of water. The temperature before adding the sodium hydroxide pellets was 25 degrees C, and after adding the pellets it was 35 degrees C. Calculate the enthalpy change in $kJ/mole$ of the reaction.

[Specific heat capacity of water $=4.2J/k/g]$

• A. $42kJ/mole$
• B. $4.2kJ/mole$
• C. $4200kJ/mole$
• D. None

Answer 1

The correct option is A $42kJ/mole$

Heat evolve $=m{C}_v\Delta t=100\times 4.2\times 10=4.2kJ$
for 0.1 mole the enthalpy change $=4.2kJ$
for 1 mole the enthalpy change $=42kJ$