Question

A system is provided with $200\text{cal}$ of heat and the work done by the system on the surrounding is $40\text{J}$. Calculate the internal energy of the system:

• A. Increases by $600\text{J}$
• B. Decreases by $800\text{J}$
• C. Increase by $800\text{J}$
• D. Increases by $160\text{J}$

Answer 1

The correct option is C Increase by $800\text{J}$

From first law of thermodynamic, $△U=q+W$
$q=200cal=200\times 4.2=840J$
$W=-40J$
$△U=q+w=840-40=800J$