Water and bonding, combustion, chemistry ocr a level

Question

1. Explain why a small proportion of molecules of water have a relative molecular mass of 20?

2. What mass of CO2 in grams, is formed by the complete combustion of 42m3, measured at RTP, of propane?

Answer 1

1. D₂O, deuterium oxide, or Heavy Water, inside a deuterium nucleus, there is one proton and one neutron therefore mass number at 2 amu; Or, H₂¹⁸O, and O at 18 amu, or HD¹⁷O and O at 17 amu..
2. RTP stands for Room TP, where T = 25C = 298.15 K and P = 1.00 atm?

if so, based on the ideal gas law, n = 1 atm * 42,000L/ [( 0.08206 atm*L/mol*K)*298.15K] = 1716.65 mol C₃H₈

combustion: C₃H₈ + 5 O₂ ---> 3 CO₂ + 4 H₂O

m (CO₂) = 1716.65 mol C₃H₈ * [ 3 mol CO₂ / 1mol C₃H₈] * [44.01 g CO₂ /1 mol CO₂ ] = 226,649.93 g

approximately 226.65 kg of CO₂