A student is given the following mixtures: (i) What do you observe in the tube containing K2Cr2O7 solution? (ii) Identify the gas produced in the first test tube A. (iii) State on physical test for th

Here are the solutions for part (e):

e) A student is given the following mixtures:

e) (i) What do you observe in the tube containing $\text{K}_2\text{Cr}_2\text{O}_7$ solution?
When sodium sulfite ($\text{Na}_2\text{SO}_3$) reacts with hydrochloric acid ($\text{HCl}$), sulfur dioxide ($\text{SO}_2$) gas is produced. Sulfur dioxide is a reducing agent. Potassium dichromate ($\text{K}_2\text{Cr}_2\text{O}_7$) solution is an orange oxidizing agent. When $\text{SO}_2$ gas is passed through the $\text{K}_2\text{Cr}_2\text{O}_7$ solution, the dichromate ions ($\text{Cr}_2\text{O}_7^{2-}$) are reduced to green chromium(III) ions ($\text{Cr}^{3+}$).
The observation is that the orange solution turns green.

e) (ii) Identify the gas produced in the first test tube A.
The reaction between sodium sulfite ($\text{Na}_2\text{SO}_3$) and hydrochloric acid ($\text{HCl}$) produces sulfur dioxide gas.

$$\text{Na}_2\text{SO}_3(\text{s}) + 2\text{HCl}(\text{aq}) \rightarrow 2\text{NaCl}(\text{aq}) + \text{H}_2\text{O}(\text{l}) + \text{SO}_2(\text{g})$$

The gas produced is sulfur dioxide ($\boxed{\text{}SO_2\text{}}$.

e) (iii) State on physical test for the gas produced in test tube A.
Sulfur dioxide is a colorless gas with a characteristic pungent smell.
A physical test for sulfur dioxide is its pungent/choking/suffocating smell.