Question

A gas occupies a volume of 40.0 milliliters at 20 c if the volume is increased too 80.0 milliliters at constant pressure, the resulting temperature will be equal to

Answer 1

Charles law gives the relationship between temperature and volume of gases. It  states that the volume of gas is directly proportional to temperature at constant pressure. 
V / T = k 
where V - volume and T - temperature in Kelvin and k - constant 
$\frac{V1}{T1} = \frac{V2}{T2}$
where parameters for the first instance are on the left side and parameters for the second instance are on the right side of the equation 
T1 - 20 °C + 273 = 293 K
substituting these values in the equation 
$\frac{40.0 mL}{293 K} = \frac{80.0 mL}{T}$
T = 586 K
temperature in celsius = 586 K - 273 = 313 °C
new temperature is 313 °C