Question

An unknown compound contains only C, H, and O. Combustion of 7.30 g of this compound produced 14.6 g CO, and 5.97 g H,O. What is the empirical formula of the unknown compound? Insert subscripts as needed. empirical formula: CHO

Answer 1

As the analysis is performed in air and typically an oxidant å added to the combustion , so only c and H of the combustion can be presumed to derive Joeom the unknown. gr is given that 14.6 g of coa and 5.97 g of Ho os überated, then :- moles of carbon & mass of carbon that reaction produces nolar mass of con = 14.6 = 0.83 mot 44 & mass of carbon = (no. of redes produced & mass) of c ç 0:33 x 12 3.96 9 of C similarly, moles of hydrogen = 2 x mass of H that reaction produces Но моя , и, о 2 2 x 5.97 = 0.66 net of H 78 (A) Here a is neith plied as in the two hydrogen atom are produced)

percentage to the original Now, finally we work out the composition of C, H, O with respect sample : % C = mass of carbon x 100% mass of reactants = 3.96 X100% = 54.24 % 7:30 % н; 44 Ищ влода) х 10 °). e mass of reachant an _ x 100% - 9.09% 0.66 7.30 % 0 a 9 100 - (54.24 + 9.04) 160 - 63,28 = 36.72%

loog of this we will After all compound work out moles of this work we assume that was present, and from the empirical formula. carbon = percentage of c. Molar moss of = 54.24 : 4.52 12 Moles of hydrogen percentage of t= 9.09 = 9.04 мол тоа е и mores of oxygen = percentage of o 2 36.72 = 2.29. Molar mass ogo Now, dividing each of the mole values obtained above by the smallest no. among them (ie. 2.29). for (= 4.52 = 1.9 ~ 2 2.29 For = 9.04 = 8.9 2 4 2.29. For 0= 2.29 = 1 2.29 Tм, и gf Me who a c:: o u 2:4:) So, the empirical formula of the reactant is Choo.