which of the following weighs the most?
(A)10^23 molecules of H2
(B)1 mole of H2O
(C)10^22 atoms of oxygen
(D)1 mole of N2

1) 1023 molecules of H2 :
Molar mass of H = 1 g mol-1
Mass of 6.022×1023 molecules = 2 g
Mass of 1023 molecules = 26.022×1023×10230.3321 g

2) 1 mole of H2O :
Molar mass of water = 18 g mol-1
Mass of 1 mole of H2O = 18 g

3) 1022 atoms of oxygen :
Atomic mass of oxygen = 16 u
Mass of 6.022×1023 atoms = 16 g
Mass of 1022 atoms = 166.022×1023×1022  = 0.265 g   

4) 1 mole of N2
Molar of N2 =  28 g mol-1
Mass of 1 mole of N2 = 28 g

Therefore , 1 mole of N2 weighs the most.

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6.022*1023 molecules of H= molar mass of H2 = 2 g. [atomic mass of H = 1 u]
Therefore, 1023 molecules of H2 = 2/6.022 = 0.3321 g

1 mole of H2O = molar mass of H2O [atomic mass of O = 16 u]
= 1*2 + 16*1
= 2 + 16
= 18 g.

6.022*1023 atoms of O = 16 g [atomic mass of O = 16 u]
1022 atoms = 16/60.22 = 0.2656 g

1 mole of N2 = molar mass of N2
= 14*2 [atomic mass of N = 14 u]
= 28 g
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