Question

1. The mass of an empty evaporating dish and watch glass is 62.549 g. After the addition of an unknown, the mass was 63.089 g. The evaporating dish and unknown were heated strongly for 10 minutes. After cooling, the mass of the evaporating dish and sample were found to be 62.928 g. A sample of the unknown was also submitted to a flame test, and found to produce a violet flame. Is the unknown NaHCO3, Na2CO3, KHCO3, or K2CO3? Explain the reasoning used to arrive at your answer.

2.2. If 0.485 g of K2CO3 were reacted according to the following equation, what would be the expected mass of the KCl product? K2CO3(s) + HCl(aq) → 2 KCl(s) + H2O(g) + CO2(g)

Answer 1

1. ANSWER : K₂CO₃

The ion responsible for violet colour is K⁺.

Na⁺ ions give yellow colour.

And as on heating the mass of the substance decreases indicated that KHCO₃ undergoes decomposition forming potassium carbonate and liberating H₂O and CO₂.

Thus on heating the salt obtained is K₂CO₃.

The reaction is represented as

Д 2KHCO3 K2CO3 (s) + H₂O(g) + CO₂(g)

2.2

OH + H. K2CO₃ tatal Cs). caq (8) HOG+ drod oo Sinoi totot 3 fotosde o 959 ? Cabiaod editie Goitoupe BY Given Reaction : moitope bici 17o7 - QKCl + H2O + CO₂(g) (9) Cleo De CA ce po molar mass of K2CO3 = 138.2059 1 mole = 138.2059 molar mass of KCI = 34.55139 Imoles = 2*74.55 13g=149.1026. According to given balanced equation, Por 138.205g of K₂CO₃ react with Hel to form of g of Kel 20.485g of K₂CO3 could react with Hel I to form ps TO 0.485g of K₂CO3 x 149.1026 8 of Kel 138.2059 of K2CO3 Answer: 0.523ag of KCl