Question

A gas originally at 27 °c and 1.00 atm pressure in a 2.6 l flask is cooled at constant pressure until the temperature is 11 °c. the new volume of the gas is

Answer 1

Charles law gives the relationship between volume and temperature of gas at constant pressure 
it states that at constant pressure, volume of gas is directly proportional to temperature 
V/T = k
where V - volume T - temperature and k - constant 
$\frac{V1}{T1} = \frac{V2}{T2}$
parameters for the first instance are on the left side of the equation and parameters for the second instance are on the right side of the equation
T1 - temperature in Kelvin - 27 °C + 273 = 300 K
T2 - 11 °C + 273 = 284 K
substituting the values in the equation 
2.6 L / 300 K = V / 284 K 
V = 2.46 L
New volume of the gas is 2.46 L