Find mass of 117.2 ml of N2 gas at STP.

Steps to Solve

1. Convert volume from milliliters to liters

To use the ideal gas law, first convert the volume of nitrogen gas from milliliters (mL) to liters (L).

$$ 117.2 , \text{mL} = 0.1172 , \text{L} $$

2. Use the ideal gas law to find moles

At Standard Temperature and Pressure (STP), 1 mole of gas occupies 22.4 L.

Calculate the number of moles of nitrogen gas using the formula:

$$ \text{moles} = \frac{\text{volume}}{\text{molar volume at STP}} $$

So,

$$ \text{moles of } N_2 = \frac{0.1172 , \text{L}}{22.4 , \text{L/mol}} $$

3. Calculate the mass of nitrogen gas

The molar mass of nitrogen gas (N₂) is approximately 28.02 g/mol.

Using the number of moles calculated in the previous step, find the mass:

$$ \text{mass} = \text{moles} \times \text{molar mass} $$

4. Substitute the values and calculate the mass

Substituting the calculated moles into the equation:

$$ \text{mass of } N_2 = \left( \frac{0.1172 , \text{L}}{22.4 , \text{L/mol}} \right) \times 28.02 , \text{g/mol} $$

5. Final calculation

Now perform the final computation:

$$ \text{mass of } N_2 \approx (0.00523) \times 28.02 \approx 0.146 , \text{g} $$