# What pressure would it take to compress 200 L of helium gas initially at 1.00 atm into a 2.00 L tank at constant temperature?

${P}_{1} {V}_{1} = {P}_{2} {V}_{2}$, given constant temperature and given quantity of gas.
${P}_{2} = \frac{{P}_{1} {V}_{1}}{V} _ 2$ $=$ $\frac{200 \cdot L \times 1.00 \cdot a t m}{2.00 \cdot L}$ $=$ $\text{A lot of atmospheres}$