Chemistry question!!!

1. Which rigid cylinder contains the same number of gas molecules as STP as a 2 liter rigid cylinder containing H2 at STP?

A. 1 liter of O2
B. 2 liters of CH4
C. 1.5 liters of NH3
D. 4 liters of He



2. A 245g sample of i2 contains approx the same number of molecules as:

A. 14g of N2
B. 2g of H2
C. 36g of H2O
D. 40g of Ne

Please explain to me HOW TO GET THE ANSWER and not the answer by itself

1. B. Equal volumes of gases contain the same number of molecules ujnder the same conditions. --Avogadro

2. Atomic weights: I=127, H=1, O=16, H2O=18

245gI2 x 1molI2/127gI2 = 1.93 mole I2, which is essentially 2 moles.

The answer is C., because 36g H2O is two moles.

1. 1 mole of any gas at STP occupies a volume of 22.4 liters.
moles H2 = 2 / 22.4 = 0.089 = 0.089 * 6.02 * 10^23
= 5.36 * 10^22 molecules because 6.02 * 10^23 molecules = 1 mole.
So the answer is B. 2 liters of CH4 which contains the same number of molecules.

2. moles = mass / molar mass.
molar mass I2 = 253.8 g/mol
mol I2 = 245 g / 254 g/mol =0.96 mol = 1 mol.
A = 14 / 14 = 1 mol, B = 2 / 2 = 1 mol,
C = 36 / 18 = 2 mol, D = 40 / 20 = 2 mol.
So a 245 g sample of I2 contains the same
number of molecule as 14 g N2 or 2g H2
so the answer is A & B.