Study the flow chart in figure below and answer the questions that follow. (a) Identify salt solution W. (b) Name another reagent that can be used in Test 1 above. (c) Write the equation for the reaction in Test 3.

Katika Test 1, chumvi W inaitikia na $\text{Ba(NO}_3)_2$ kutoa white precipitate. Hii inaashiria uwepo wa ioni za sulfati ($\text{SO}_4^{2-}$), kwani $\text{BaSO}_4$ ni white precipitate isiyoyeyuka. Katika Test 2, white precipitate hii haiyeyuki katika $\text{HCl}$ (aq), ikithibitisha kuwa ni $\text{BaSO}_4$. Hivyo, chumvi W ina ioni za sulfati.

Katika Test 3, chumvi W inaitikia na excess $\text{NaOH}$ (aq) kutoa colourless solution. Hii inaashiria uwepo wa ioni za metali ambazo huunda precipitate nyeupe inayoyeyuka katika excess $\text{NaOH}$. Ioni za $\text{Al}^{3+}$ na $\text{Pb}^{2+}$ huonyesha tabia hii. Katika Test 4, chumvi W inaitikia na excess $\text{NH}_3$ (aq) kutoa white precipitate. Hii inaashiria uwepo wa ioni za $\text{Al}^{3+}$ kwani $\text{Al(OH)}_3$ ni white precipitate isiyoyeyuka katika excess $\text{NH}_3$, tofauti na $\text{Pb(OH)}_2$ ambayo ingeyeyuka kidogo.

Kutokana na matokeo ya Test 1, 2, 3, na 4, chumvi W ina ioni za $\text{Al}^{3+}$ na $\text{SO}_4^{2-}$.
Hivyo, chumvi W ni Aluminium Sulphate.