The molar masses of each element are:
Ba =137.3 g/mol
N = 14 g/mol
O = 16 g/mol
Calculating the total mass by multiplying with number of moles:
Ba = 137.3 g/mol * 1 mol = 137.3 g
N = 14 g/mol * 2 mol = 28 g
O = 16 g/mol * 6 mol = 96 g
Total 261.3g
Ba: 137.3/261.3 = 52.55%
N: 96/261.3 = 36.73%
O: 24/261.3 = 10.72%
Answer:
52.55% Ba, 10.72% N, 36.73% O