Answer: New pressure inside the flask would be 148.8 kPa.
Explanation: The combined gas law equation is given by:

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



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

Putting the values, in above equation, we get

In order to make the dissolution of the solid compound in water to occur at a faster rate, Samuel could do the following:
1. Break down the solid into tiny particles: breaking down the solid into tiny particles increases the surface area of the solid and thus increase the quantity of the substance that comes in contact with the solvent per time, this leads to a faster dissolution of the solid.
2. Stir the liquid with iron rod: Samuel can increase the dissolution rate of the substance by stirring it continuously with iron rod.
3. Increasing the temperature:Samuel could also increase the rate of dissolution of the substance by increasing the temperature of the water.
Mass of this substance = 9.928 g
<h3>Further explanation</h3>
Molarity is a way to express the concentration of the solution
Molarity shows the number of moles of solute in every 1 liter of solute or mmol in each ml of solution

Where
M = Molarity
n = Number of moles of solute
V = Volume of solution
So to find the number of moles can be expressed as

mol of substance -Lithium nitrite - LiNO₂ :
V = 250 ml = 0.25 L
M = 0.75 M

So mass of this substance - LiNO₂ (MW=52,947 g/mol) :
