Using the molar volume in calculations with chemical equations
4 marks · NormalAmmonium nitrate decomposes to form dinitrogen oxide (N2O) and water. The balanced equation is:
A practical uses 8.0 g of ammonium nitrate. (Ar: N = 14, H = 1, O = 16; molar volume at rtp = 24 dm³)
Calculate the number of moles of ammonium nitrate used.
Calculate the volume, in dm³, of dinitrogen oxide (N₂O) formed at rtp.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) 0.10 mol
(b) 2.4 dm³ dm^3
Show mark scheme and worked solution
Marking points
M1 (a) · 1 mark · Finds Mr of NH₄NO₃ (14×2 + 4×1 + 3×16 = 80)
A1 (a) · 1 mark · Correct calculation of moles (8.0/80 = 0.10 mol) (follow-through)
M2 (b) · 1 mark · Uses equation 1:1 mole ratio for N₂O
A2 (b) · 1 mark · Multiplies by proper molar volume (0.10 × 24 = 2.4 dm³, accept ecf) (follow-through)
Worked solution
a) Calculate Mr of NH₄NO₃: (2×14) + (4×1) + (3×16) = 28 + 4 + 48 = 80
b) 1 mole NH₄NO₃ produces 1 mole N₂O. So moles of N₂O = 0.10
Volume = moles × molar volume = 0.10 × 24 = 2.4 dm³