chem 9/28/2015 11:55 PM 12.5/20 PrintCalculatorPerodic Table stion 2 of 20 Incor

Question

chem 9/28/2015 11:55 PM 12.5/20 PrintCalculatorPerodic Table stion 2 of 20 Incorrect apling learçing A compound is 54.53% C, 9.15% H, and 36.32% O by mass. What is its empirical for Insert subscripts as needed. The molecular mass of the compound is 132 amu. What is the molecular formula? CHO Insert subscripts as needed. There is a hint available! View the hint by clicking on the bottom divider bar. Click on the divider bar again to hide the hint Close Previous Give Up & View Solution D Check Hint careers partne

Explanation / Answer

Q.1: consider 100 g of the organic compound.

Mass of C in 100 g of compound = 54.53 g

Moles of C in 100 g of compound = 54.53 g / 12 gmol-1  = 4.54 mol C

Mass of H in 100 g of compound = 9.15 g

Moles of H in 100 g of compound = 9.15 g / 1.007 gmol-1  = 9.08 mol H

Mass of O in 100 g of compound = 36.32 g

Moles of O in 100 g of compound = 36.32 g / 16 gmol-1  = 2.27 mol O

mole ratio of C, H and O is

4.54 mol C : 9.08 mol H : 2.27 mol O

Dividing the above mole ratio by smallest number 2.27 we get

(4.54 / 2.27)mol C : (9.08/2.27) mol H : (2.27 / 2.27) mol O

= 2 mol C : 4 mol H : 1 mol O

Hence the empirical formulae of the compound is C2H4O (answer)

Empirical formulae mass of the compound = 2x12 + 1x4 + 16

Given the molecular mass of the compound is 132 u

n-factor for the compound, n = 132 u / 44 u = 3

Hence molecular formulae of the compound = 3 x (C2H4O) = C6 H12 O3   (answer)

Q.2: The balanced chemical reaction is

2 NaN3(s) --- > 3 N2(g) + 2 Na(s)

Reactant : Number of Na atoms = 2x1 = 2

Number of N atoms = 2x3 = 6

Product: Number of Na atoms = 2x1 = 2

Number of N atoms = 3x2 = 6

Q.3: The given unbalanced chemical reaction is

Li3N + H2O ----> LiOH + NH3

Li = 3 , N = 1 Li = 1, N = 1

H = 2 , O =1 H = 4 , O = 1

There are 3 Li on reactant side and only 1 on product side. Hence we need to multiply LiOH by 3.

Now if we multiply H2O on reactant side by 3, H and O will be balanced.

Hence the balanced chemical reaction is

Li3N + 3 H2O ----> 3 LiOH + NH3 (answer)

Q.4: The given balanced chemical reaction is

2 HCl + Ca(OH)2 ----> CaCl2 + 2 H2O

2 mol 1 mol 1 mol 2 mol

Mass of HCl = 31.4 g

molecular mass of HCl = 36.5 gmol-1

Hence moles of HCl = mass / molecular mass = 31.4 g / 36.5 gmol-1 = 0.860 mol HCl

Moles of CaCl2 formed = 0.860 mol HCl x (1 mol CaCl2 / 2 mol HCl) = 0.430 mol CaCl2

Hence moles of CaCl2 formed is 0.430 mol (answer)

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