Answer:
130.159
Step-by-step explanation:
P=0.987
V=66ml =66/1000=0.066 L
n/moles= ?
R=0.08206
T=86.9+273.15=360.5 K
Formula PV=RnT
n =PV/TR
n=(0.987 * 0.066)/(360.05 * 0.08206) = 0.002205
Now to obtain molar mass you divide grams by mol.
0.287/0.002205 = 130.159