Peroxyacylnitrate (PAN) is one of the components of smog. It is a compound of C,

Question

Peroxyacylnitrate (PAN) is one of the components of smog. It is a compound of C, H, N and 0. Determine the percent composition of oxygen and the empirical formula from the following percent composition by mass: 19.8 percent C, 2.50 percent H, 11.6 percent N. What is its molecular formula given that its molar mass is about 120 g? Tin (II) fluoride (SnF2) is often added to toothpaste as an ingredient to prevent tooth decay. What is the mass of F in grams in 24.6 g of the compound? Lactic acid, which consists of C, H, and 0, has long been thought to be responsible for muscle soreness following strenuous exercise. Determine the empirical formula of lactic acid given that combustion of a 10.0 g sample produces 14.7 g CO_2 and 6.00 g H_20.

Explanation / Answer

1) Let the formula of the compound be CxHyNzOm

Let there be 100 g of the compound

Thus, mass of C = 19.8 g

moles of C = mass/molar mass = 19.8/12 = 1.65

mass of H = 2.5 g

Thus, moles of H = mass/molar mass = 2.5/1 = 2.5

Mass of N = 11.6 g

Thus, moles of N = mass/molar mass = 11.6/14 = 0.83

Mass of O = 66.1

moles of O = mass/molar mass = 66.1/16 = 4.13

Thus, C,H,N & O are present in the molar ratio of C1.65H2.5N0.83O4.13 or, C2H3N1O5

Empirical mass of the compound = 121 g/mole

Thus, molecular formula = empirical formula

2) Molar mass of SnF2 = 156.7 g/mole

Thus, moles of SnF2 in 24.6 g of it = mass/molar mass = 24.6/156.7 = 0.157

Thus, moles of F = 2*moles of SnF2 = 0.314

Mass of F = moles*molar mass = 0.314*38 = 11.93 g

3) Moles of CO2 formed = mass/molar mass = 14.7/44 = 0.334

Thus, moles of C = moles of CO2 = 0.334

mass of C = moles*molar mass = 0.334*12 = 4.01

Moles of H2O formed = mass/molar mass = 6/18 = 0.334

moles of H = 2* moles of H2O = 0.668

mass of H = moles*molar mass = 0.668*1 = 0.668 g

Thus, mass of O = 10 - 4.01 - 0.668 = 5.322 g

moles of O = mass/molar mass = 0.333

Thus, C,H& O are present in the molar ratio of 0.334:0.668:0.334

Thus, the empirical formula is CH2O

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