EXPERIMENT Pre-Lab Questions 1. Carbon dioxide, CO, is a common gas. It is found

Question

EXPERIMENT Pre-Lab Questions 1. Carbon dioxide, CO, is a common gas. It is found in the atmosphere, and we expel it when we breathe out in respiration. Determine: (a) the empirical formula; (b) the molecular formula; (c) the percent composition of carbon; (d) the percent composition of oxygen 2. The molecular formula of para-dichlorobenzene, a compound found in some commercial mothballs, is CoHyCl. What is the simple whole number ratio of the elements? What is the empirical formula? 3. Given the following molecular formulas, write the empirical formulas. Empirical Formula Molecular Formula CHio (butane) CoHs (naphthalene) CH12Os glucose) 4. Calculate the percentage by weight of chloride ion (C) in common salt, NaCI. Show your work 57

Explanation / Answer

Ans 1 :

a) The empirical formula represent the simplest ratio of elements present in the compound.

Carbon dioxide is CO2 , here the elemental ratio is 1 : 2 . which is simplest , so the empirical formula of the compound will be CO2.

b) The molecular formula as the name suggests is CO2 . There are two atoms of oxygen , per atom of carbon in each molecule.

c) The molar mass of the gas is 44.01 g/mol

Each mole of CO2 has one mole atoms of carbon = 12.01 g/mol

So the percent composition of carbon = ( 12.01 / 44.01 ) x 100

= 27.29 %

d)

Each mole of CO2 has 1 mole of molecule of oxygen = 32.000 g/mol

So the percent compoistion of oxygen = ( 32.000 / 44.01) x 100

= 72.71 %

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