Q.1. How many moles of oxygen molecules are present in 112 mL of O2 gas at NTP?
we know that,
22400 mL of O2 gas contains 1 mole of O2
112 mL of O2 gas contains 112/22400 mol of O2
= 0.005 mol of O2 gas.
Hence, 0.005 moles of oxygen molecules are present in112 g of O2 at NTP.
Q.2. How many molecules are contained in 0.35 mol of N2?
we know that,
1 mole of N2 will contain 6.002 * 10 23 molecules of N2.
0.35 mole of N2 will contain 0.35 * 6.002 * 10 23 molecules of N2 .
= 2.17 * 10 23 molecules of N2 .
Hence, there are 2.17 * 10 23 molecules of N2 are present in 0.35 mol of N2.
Q.3. How many moles of atoms are contained in 15 g of Zn?
we know that ,
mass of Zn is 65.4
now, no of moles of atoms = mass in g/ atomic mass
= 15/65.5 = 0.23 mol.
0.23 moles of atoms is contained in 15 g of Zn.