A mixture of Na2CO3 and MgCO3 of mass 7.63 g is reacted with an excess of hydrochloric acid. The CO2 gas generated occupies a volume of 1.67 L at 1.24 atm and 26 degree C. From these data, calculate the percent composition by mass of Na2CO3 in the mixture

Respuesta :

Answer:

58.6 % by mass of Na₂CO₃

Explanation:

This is the reaction:

Na₂CO₃  +  MgCO₃ +  4HCl  →  MgCl₂  +  2NaCl  + 2CO₂  +  2H₂O

Let's find out the moles of CO₂ produced, by the Ideal Gases Law

1.24 atm . 1.67 L = n . 0.082 . 299K

(1.24 atm . 1.67 L / 0.082 . 299K) = n

0.0844 moles = n

Ratio is 2:1, so 2 moles of dioxide were produced by 1 mol of sodium carbonate. Let's make a rule of three:

2 moles of CO₂ were produced by 1 mol of Na₂CO₃

Then, 0.0844 moles of Co₂ would beeen produced by (0.0844 .1)/2  = 0.0422 moles of Na₂CO₃.

Let's convert this moles into mass (mol . molar mass)

0.0422 mol . 106 g/mol = 4.47 g

Finally we can know the mass percent of sodium carbonate in the mixture

(Mass of compound /Total mass) . 100 → (4.47 g / 7.63g) . 100 = 58.6 %

The percent composition by mass of Na₂CO₃ in the mixture is 58.6%

Firstly, write the chemical reaction involved in this:

Na₂CO₃+MgCO₃+4HCl → 2NaCl+2CO₂+2H₂O

We need to find the number of moles of CO₂.

Number of moles (n)=[tex]\frac{1.24 atm * 1.67 L}{0.082 *299K}[/tex]

n=0.0844 moles

So, 1 mol of sodium carbonate produces 2 moles of carbon dioxide.

OR

2 moles of CO₂ were produced by 1 mol of Na₂CO₃.

Then, 0.0844 moles of CO₂ will be= [tex]\frac{1}{2}[/tex]×0.0844=0.0422 moles of Na₂CO₃

In order to get the answer in mass, we need to convert moles into molar mass.

Molar mass of Na₂CO₃= 106g/mol

Molar mass for 0.0422 mol of Na₂CO₃=0.0422×106=4.47 g

In order to find the mass percentage which is given by:

Mass percentage= Mass of Compound/ Total Mass *100

=(4.47g / 7.63g)*100= 58.6%

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