Question

a closed flask of air (0.250 L) contains 5.00 "puffs" of particles. The pressure probe on the flask reads 93 kPa. A student uses a syringe to add an additional 3.00 "puffs" of air through the stopper. Find a new pressure inside the flask.

Answer 1

Answer: New pressure inside the flask would be 148.8 kPa.

Explanation: The combined gas law equation is given by:

$PV=nRT$

As the flask is a closed flask, so the volume remains constant. Temperature is constant also.

So, the relation between pressure and number of moles becomes

$P=n\\or\\\frac{P}{n}=constant$

$\frac{P_1}{n_1}=\frac{P_2}{n_2}$

• Initial conditions:

$P_1=93kPa\\n_1=5\text{ puffs}$

• Final conditions: When additional 3 puffs of air is added

$P_2=?kPa\\n_2=8\text{ puffs}$

Putting the values, in above equation, we get

$\frac{93}{5}=\frac{P_2}{8}\\P_2=148.8kPa$