Question

A flexible container at an initial volume of 7.14 L contains 5.51 mol of gas. More gas is then added to the container until it reaches a final volume of 17.1 L. Assuming the pressure and temperature of the gas remain constant, calculate the number of moles of gas added to the container.

Answer 1

Let's assume that x is the number of moles of added gas. Now we can make a proportion:

5.51 moles of gas occupies 7.14 L;

(5.51 + x) moles of gas occupies 17.1 L;

Now we can cross-multiply the terms of proportion to get the final equation:

5.51mol*17.1L=7.14L * (5.51 + x)mol;

To get the x value, let's divide both sides by 7.14L and subtract 5.51 from both sides:

$$\frac{5.51mol*17.1L}{7.14L} - 5.51mol=x mol;$$

x=7.68 moles;

Answer: there are 7.68 moles of gas added to the container.