AP Chemistry Predicting Products Tutorial

Answers to Double Replacement #16-30

16. A 50 milliliter sample of 0.10 M hydrochloric acid is added slowly with stirring to a 50

milliliter sample of 0.10 M sodium carbonate solution.

2H+ + Cl- + Na+ + CO32- Na+ + Cl- + H2CO3 Na+ + Cl- + CO2 + H2O

net ionic: 2H+ + CO32- CO2 + H2O

Note: H2CO3 decomposes into CO2 and water. See “Stuff I should know for the ap test but

don’t know yet”

17. Hydrogen sulfide is bubbled through a solution of silver nitrate.

H2S + 2Ag+ + NO3- Ag2S + 2H+ + NO3-

Net ionic: H2S + 2Ag+ Ag2S + 2H+

18. Excess silver acetate is added to a solution of trisodium phosphate.

3Ag+ + 3C2H3O2- + 3Na+ + PO43- 3Na+ + 3C2H3O2- + Ag3PO4

net ionic: 3Ag+ + PO43- Ag3PO4

19. Solid sodium cyanide is added to water

2NaCN + H2O 2Na+ + O2- + 2HCN

20. Manganese(II) nitrate solution is mixed with sodium hydroxide solution.

Mn2+ + NO3- + Na+ + 2OH- Na+ + NO3- + Mn(OH)2

Net ionic: Mn2+ + 2OH- Mn(OH)2

21. Equal volumes of dilute equimolar solutions of sodium carbonate and hydrochloric acid are mixed.

2Na+ + CO32- + 2H+ + 2Cl- 2Na+ + 2Cl- + H2CO3 2Na+ + 2Cl- + CO2 + H2O

Net ionic: CO32- + 2H+ CO2 + H2O

22. Solid barium peroxide is added to cold dilute sulfuric acid.

BaO2 + 2H+ + SO42- BaSO4 + H2O2

Note: the oxidation states do not change in double replacement reactionsperoxide (O22-)

must stay peroxide so the oxidation state of O doesn’t change.

23. Dilute acetic acid solution is added to solid magnesium carbonate.

2HC2H3O2 + MgCO3 Mg2+ + 2C2H3O2- + CO2 + H2O

24. Solid magnesium nitride is added to excess deuterium oxide.

Mg3N2 + 3H2O 2NH3 + 3MgO

25. Gaseous hydrofluoric acid reacts with solid silicon dioxide.

4HF + SiO2 SiF4 + 2H2O

Note: Si must have an oxidation of +4 in order for SiO2 to be neutral. Therefore, Si and F

must bond in a 1:4 ratio.

26. Equimolar amounts of trisodium phosphate and hydrogen chloride, both in solution, are mixed.

3Na+ + PO43- + 3H+ + 3Cl- H3PO4 + 3Na+ + 3Cl-

net ionic: PO43- + 3H+ H3PO4

27. A saturated solution of calcium hydroxide is added to a solution of magnesium chloride.

Ca2+ + 2OH- + Mg2+ + 2Cl- Ca2+ + 2Cl- + Mg(OH)2

Net ionic: 2OH- + Mg2+ Mg(OH)2

28. Solid silver sulfide is warmed with dilute nitric acid.

Ag2S + 2H+ + NO3- H2S + 2Ag+ + NO3-

Net ionic: Ag2S + 2H+ H2S + 2Ag+

29. Hydrogen sulfide gas is added to a solution of cadmium nitrate.

H2S + Cd2+ + 2NO3- CdS + 2H+ + 2NO3-

Net ionic: H2S + Cd2+ CdS + 2H+

30. Dilute sulfuric acid is added to a solution of lithium hydrogen carbonate.

2H+ + SO42- + 2Li+ + 2HCO3- 2Li+ + SO42- + 2CO2 + 2H2O

net ionic: H+ + HCO3- CO2 + H2O