Question

7. Write the empirical formula for the following compounds. (a) naphthalene, CHE (b) pyrene, Chio (c) N:02 (d) glucose, C.H1206 8. Complete and balance the following chemical equations for the complete combustion of hydrocarbons. (a) CsH(g) + O2(8) - (b) CsH10 (g) + 02 (8) - 9. Calculate the percent composition of the following compounds: (a) Na:0 (b) Na2CO3 10. Which of the following hydrocarbon contains greater percentage of carbon by mass? (a) naphthalene, CiH, and (b) anthracene, CH 10

Answer 1

@ Naphthalene CloHg Naphthalene, the simplest of the fused or com ning hydrocarbon compounds composed of ving sharing two adjacent carbon atoms, us empirical formula for Naphthalene is czotiga 6 Pyrene GOHIO ene is the condensed ning hydrocarbon of four benzene ring. This empirical for pyrene is GoHo Na Oz The empirical formula for a compound is one that expreses the smallest whole number ralio of atom present This empirical formula for N2O2 is No glucose, CH12O6 empirical formula for glucose = CH₂O. 00, @ Cz Hq + O2 CO2 + H2O hydro carbon reacts with Onygen to create carbon -dioxide , water and heat. This is called hydrocarbon combustion balanced equation for above reaction. 3 Hg + 502 - 300 + 4H₂O. 568 +400 - 40502+ 2C8H₂ + 2102 16CO₂ + 10H₂O.

Molecular weight 46+16 = 62 g/mol %. Na = weight of Na x100 I weight of Nazo DO = 46x100 62 = 0.7419 X 100 - 74:19 %. %. Oxygen = bood 100 - t. of Nanos de = 100 -74.19 = 25.81./ NaCO3 weight of Na co₂ = 46+12+48 = 106 7. Na = 46 x 100 ③ = 0.43396X100 = 43.34 %. %. C = 12 x 100 106 = 11.327 48 X100 % 0 106 = = 0.4528 x 100 45.284

© @ Naphthalene Goto Mint = 120+8 = 128 anthracene GAH 10 m.wt = 12x14410 = 178 7. C= 120x100 soc= 168 x 100 178 128 0.9375X100 93.75.4 = = = 0.9438 X 100 = 94.38% This Anthracene by mass. has greater percentage of carbon