# To expel half the mass of air from a large flask at $27^{\large\circ}C$ , it must be heated to

$(a)\;54^{\large\circ}\qquad(b)\;177^{\large\circ}\qquad(c)\;277^{\large\circ}\qquad(d)\;327^{\large\circ}$

PV = nRT
at constant P and V
$n_1T_1 = n_2T_2$
$n_1\times100 = \large\frac{n_1}{2}\times T$
T = 600K
$=327^{\large\circ}C$