Question

Experiment 9- Decomposition of Baking Soda

A. mass of H2CO3 gas released, (H2CO3 decomposed into H2O + CO2)?

B. mass of NaHCO3 in unknown mixture?

C. mass of NaHCO3 in unknown mixture?

D. mass of KCL in unknown mixture?

CURCU ILI U ULICOS MOLLE (Part 2) Percent of NaHCO3 in an Unknown Mixture 1) Weigh out approximately 1 g of the unknown sample into your cruci 2) Repeat the steps of the previous procedure. ne steps of the previous procedure. This time, however, the resulting mass o expected Na2CO3 plus the unreactive component of the unknown. 3) Use the mass lost in the experiment (H20 gas +CO2 gas) to determine in your unknown sample. H30 gas +CO2 gas) to determine the mass of NaHCO3

Answer 1

Ans:

Experiment 9 - Decomposition of Baking Soda - It is givn that ---

A. Mass of unknown mixture before heating                  = 1 g

B. Mass of unknown mixture after heating                     = 0.8 g

The decomposition takes place as per below balanced reaction:

                                             ΔH

2NaHCO3 (s) → Na2CO3 (s) + H2CO3

H2CO3 → H2O (g) + CO2 (g)

Molar Masses needed for calculations:

NaHCO3              = 84 g/mole

H2CO3             = 62 g/mole

Wt. of the unknown mixture (NaHCO3 + KCl)                = 1 g

Wt. loss (Mass of H2CO3) after heating (A-B) = 1g – 0.8 g = 0.2 g

Weight of the H2CO3 gas (H2O+CO2) released             = 0.2 g

From th balanced reaction we know that th one mole of

H2CO3 (62 g) is lost by the heating of 2 moles of NaHCO3 (84 *2 = 168 g)

In practical experiment we observed the weight loss = 0.2 g

The 62 g of H2CO3 is lost by wt. of the NaHCO3 = 168 g

So, 0.2 g will be lost by heating = (168 / 62) * 0.2 = 0.542 g of NaHCO3

Hnce, the Sample taken before heating contains = 0.542 g of NaHCO3

The amount of KCl present in the mixture would be = (1 g mixture - 0.542 g of NaHCO3) = 0.458 g

Final Answers:

A. Mass of H2CO3 gas (H2O + CO2) released                 = 0.2 g

B. Mass of NaHCO3 in unknown mixture = 0.542

C. Mass of KCl in unknown mixture = 0.458 g