The approximate temperature is 20 °C.
To solve this problem, we can use the Ideal Gas Law
In the formula,
We want to solve the Ideal Gas Law for
Substituting values, we get
Notice how the units cancel to give the temperature in kelvins.
Now we convert to the Celsius temperature:
290 K = (290 - 273.15)°C ≈ 20 °C
Note: I have calculated the answer to only 1 significant figure, because the number of moles and the volume had only 2 significant figures.
The calculated Kelvin temperature had only 2 significant figures. When we subtracted 273.15, we lost one of these significant figures. If you need more precision, you will have to recalculate.