The combined gas law is to be used
(P_1V_1)/T_1 = (P_2V_2)/T_1P1V1T1=P2V2T1
Where P = pressure(in atm)
V = volume(in litres)
T = temperature in kelvin
convert the units to the appropriate units
T_1 = 33^oC + 273K = 306KT1=33oC+273K=306K
V_1 = 774mL = (774mL)/(1000mL) = 0.774LV1=774mL=774mL1000mL=0.774L
V_2 = 1229mL = (1229mL)/(1000mL) = 1.229LV2=1229mL=1229mL1000mL=1.229L
T_2 = 51^oC + 273K = 324KT2=51oC+273K=324K
P_2 = 1.5atmP2=1.5atm
Plug in the variables
(P_1 xx 0.774L)/(306K) = (1.5atm xx 1.229L)/(324K)P1×0.774L306K=1.5atm×1.229L324K
(P_1 xx 0.774L)/(306K) = 0.00569P1×0.774L306K=0.00569
0.00253xxP_1 = 0.005690.00253×P1=0.00569
P_1 = 0.00569/0.00253 = 2.249atmP1=0.005690.00253=2.249atm