Question

BACKGROUND INFORMATION Read "4.7 Precipitation Reactions" (Page 169 - 172) in the textbook. PRE-LABORATORY QUESTIONS 1. Explain why elements Si, Al, and Fe, which are abundant in the Earth's crust, are not abundant in seawater. 2. Define precipitate and precipitation reactions. 3. Identify the following compounds as either "soluble" or "insoluble". Soluble? Soluble? Compound NaCl AgCI AgNO3 Ag2SO4 Hg2SO4 Compound CaCl2 Ca(NO3)2 CaSO: CaCO3 Pb3(PO4)2 4. Write a net ionic equation for the reaction between an aqueous solution of lead(II) nitrate Pb(NO3)2 and an aqueous solution of sodium iodide Nal.

Answer 1

Answer (1) This is because the oxidised forms of Fe , Si, Al (salts of Fe, Si and Al) are not much soluble in water.

Answer (2):- Precipitation reaction is a type of chemical reaction in which two soluble salts in their aqueous solutions reacts and one of the products formed is an insoluble solid salt. This insoluble solid salt is called "precipitate". For e.g:-

NaCl (aq) + AgNO₃ (s) $\rightarrow$ AgCl (s) + NaNO₃ (aq)

Answer (3):-

Compound	Soluble	Compound	Soluble
NaCl	soluble	CaCl2	soluble
AgCl	insoluble	Ca(NO3)2	soluble
AgNO3	soluble	CaSO4	soluble
Ag2SO4	Insoluble	CaCO3	insoluble
Hg​​​​​​​2​​​​​​​SO4	insoluble	Pb​​​​​​​3(PO4)2	insoluble

Answer (4):- Net ionic reaction between aqueous solution of lead(II) nitrate and aqueous sodium iodide:

Pb²⁺ (aq) + 2 I^- (aq) $\rightarrow$ PbI₂ (s)