Worksheet # 11 - University of Florida

Worksheet # 11

1. A solution of sodium chloride is mixed with a solution of lead (II) nitrate. A

precipitate of lead (II) chloride results, leaving a solution of sodium nitrated.

Determine the class of reaction. The choices are decomposition, combination, singledisplacement, double-displacement, and combustion.

2. Solid sulfur is ignited and burns in oxygen gas with a blue flame to form sulfur

dioxide. Determine the class of reaction. The choices are decomposition,

combination, single-displacement, double-displacement, and combustion.

3. Balance the following equations and classify the reactions as decomposition,

combination, single-displacement, double-displacement, or combustion.

a. GaH3 + N(CH3)3 ? (CH3)3NGAH3

b. GeCl2 + Cl2 ? GeCl4

c. N2 (g) + CaC2 (s) ? C (s) + CaNCN

d. N2 (g) + Mg (s) ? Mg3N2

e. NH4Cl (s) ? NH3(g) + HCl (g)

f. CaO (s) + SO3 ? CaSO4 (s)

g. PCl5 (g) ? PCl3 (g) + Cl2 (g)

h. Ca3N2 (s) + H2O (l) ? Ca(OH)2 (aq) + NH3 (g)

4. When heated, nickel (II) carbonate undergoes a decomposition reaction. Write a

balanced equation to describe this reaction

5. When heated, platinum (IV) chloride undergoes a decomposition reaction. Write a

balanced equation to describe this reaction

6. Complete and balance the equation for the following decomposition reactions. All

reactions are heated.

a. Cu(OH)2 (s) ?

b. HgO (s) ?

7. Sodium metal reacts with chlorine gas in a combination reaction. Write a balanced

equation to describe this reaction.

8. Complete and balance each of the following combination reactions:

a. Li2O (s) + H2O (l) ?

b. SO2 (g) + O2 (g) ?

c. CaO (s) + H2O (l) ?

9. Zinc metal reacts with a solution of tin (II) chloride in a single- replacement reaction.

Write a balanced equation to describe this reaction.

10. Iron metal reactions with a solution of copper (II) sulfate in a single-displacement

reaction. Write a balanced equation to describe this reaction.

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11. Consider the following metals. Determine which will react with water and which will

react with a solution of hydrochloric acid. Write a balanced equation to describe any

equation that occurs.

a. Cr

b. Bi

c. K

12. Complete and balance each of the following single-displacement reactions.

a. Al (s) + CuSO4 (aq) ?

b. Cs (s) + H2O (l) ?

13. Which of the following single-replacement reactions will actually occur if the

indicated reagents are mixed?

a. Ni (s) + FeCl2 (aq) ? NiCl2 (aq) + Fe (s)

b. 2 Al (s) + 3 NiCl2 (aq) ? 2 AlCl3 (aq) + 3 Ni (s)

c. Fe (s) + CuCl2 (aq) ? FeCl2 (aq) + Cu (s)

d. 3 Sn (s) + 2 AlCl2 (aq) ? 3 SnCl2 (aq) + 2 Al

Answers to Worksheet # 11

1.

From the description we learn that the there are two reactants: sodium chloride

and lead(II) nitrate. These are both compounds. There are also two products:

lead(II) chloride and sodium nitrate. Since these are also compounds, the reaction

is double-displacement (2 compounds as reactants and 2 compounds as products).

2.

The reactants are solid sulfur and oxygen gas. These are both elements. Since

there is only one product, sulfur dioxide, which is a compound, this is a

combination reaction (2 elements or compounds as reactants and 1compound as

the product).

3.

For help classifying reactions, refer to Table 5.1 (Bauer p. 167). We can classify

two of the types on the number of products and reactants in the chemical

equation. In combination reactions, 2 substances combine to form 1 new

substance; in decomposition reactions, 1 compound forms several new

substances. Equations indicating 2 reactants and 2 products represent either

single- or double-displacement reactions. If 1 of the reactants and 1 of the

products is an element, the reaction is single-displacement.

(a) combination: GaH3 + N(CH3)3 ¡ú (CH3)3NGaH3

(b) combination: GeCl2 + Cl2 ¡ú GeCl4

(c) single-displacement: N2(g) + CaC2(s) ¡ú 2C(s) + CaNCN(s)

(d) combination: N2(g) + 3Mg(s) ¡ú Mg3N2(s)

(e) decomposition: NH4Cl(s) ¡ú NH3(g) + HCl(g)

(f) combination: CaO(s) + SO3(g) ¡ú CaSO4(s)

(g) decomposition: PCl5(g) ¡ú PCl3(g) + Cl2(g)

(h) double-displacement: Ca3N2(s) + 6H2O(l) ¡ú 3Ca(OH)2(aq) + 2NH3(g)

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4.

Carbonate-containing compounds (except Group IA (1)), when heated, produce

the metal oxide and carbon dioxide gas (Table 5.2). In this case, we know that

nickel has a 2+ charge to balance the charge of the 2? carbonate ion. The oxide

will be NiO. The balanced chemical equation is NiCO3(s) ¡ú NiO(s) + CO2(g).

5.

When chloride-containing compounds are heated they decompose, forming

chlorine gas and the elemental metal (Table 5.2). In this case, platinum(IV)

chloride, PtCl4, decomposes to produce platinum metal, Pt, and chlorine gas, Cl2.

The balanced chemical equation is PtCl4(s) ¡ú Pt(s) + 2Cl2(g). Note: Most ionic

compounds (such as PtCl4) are solids, and molecular chlorine is a gas.

6.

See Table 5.2 (Bauer p 168).

(a) Cu(OH)2(s) ¡ú CuO(s) + H2O(g)

Hydroxides decompose to the metal oxide with the loss of water (as a vapor or

gas). Even at the high temperatures needed to decompose many of these

compounds, ionic compounds remain in the solid state.

(b) 2HgO(s) ¡ú 2Hg(l) + O2(g)

Oxides of Au, Pt, and Hg decompose to the pure metal and oxygen gas.

7.

2Na(s) + Cl2(g) ¡ú 2NaCl(s)

Combination reactions result in the formation of 1 product from 2 reactants. If

the reactants are a metal and a nonmetal, we can reliably predict that the metal

will form a cation and the nonmetal will form an anion. When molecular

chlorine, Cl2, reacts with metals, the chlorides of the metals are formed. Sodium

is a Group IA (1) metal so it will form a 1+ ion. The formula for chloride ion is

Cl?. The formula for the metal chloride is NaCl (salt).

8.

Combination reactions result in the formation of 1 product from 2 reactants.

(a) Li2O(s) + H2O(l) ¡ú 2LiOH

By combining Li2O and H2O we could arrive at several different products.

Metal oxides combine with water to form hydroxides. In this case, the

hydroxide would result from the combination of lithium ions, Li+, and

hydroxide ions, OH?. The product for this reaction is LiOH.

(b) 2SO2(g) + O2(g) ¡ú 2SO3(g)

By combining the SO2 and O2 we could arrive at several different products

(either SO4 or SO3). In this case, the correct product is SO3.

(c) CaO(s) + H2O(l) ¡ú Ca(OH)2(aq)

By combining CaO and H2O we could arrive at several different products.

Metal oxides combine with water to form hydroxides. In this case, the

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hydroxide would result from the combination of calcium ions, Ca2+, and

hydroxide ions, OH?. The product for this reaction is Ca(OH)2.

9.

In a single-displacement reaction, 1 element displaces its ionic counterpart from a

compound. That is, a metal displaces the metal ion or a nonmetal displaces the

nonmetal ion. The formulas for the products are determined by the element or

ions that are produced (i.e. metal or diatomic molecules, etc.). When Zn displaces

Sn, Zn will form a 2+ ion (Figure 3.12). In this single-displacement reaction, the

formula for the anion remains unchanged. Since the formula for chloride ion is

Cl?, the product is ZnCl2. The balanced equation is:

Zn(s) + SnCl2(aq) ¡ú ZnCl2(aq) + Sn(s)

10.

11.

12

In a single-displacement reaction, 1 element displaces its ionic counterpart from a

compound. That is, a metal displaces the metal ion or a nonmetal displaces the

nonmetal ion. The formulas for the products are determined by the element or

ions that are produced (i.e. metal or diatomic molecules, etc.). When Fe displaces

Cu, Fe will form a 2+ ion. In this single-displacement reaction, the formula for

the anion remains unchanged.

Fe(s) + CuSO4(aq) ¡ú Cu(s) + FeSO4(aq)

In reactions of metals with hydrochloric acid solutions or water, one product will

always be hydrogen gas (H2). To determine whether a reaction takes place,

compare the activity of the metal (not the metal ion found in the product) with the

activity of hydrogen gas (Figure 5.21). If the metal is higher in the activity series

than hydrogen gas, a reaction will take place. Some metals are more active than

others. Those that are more active react under less extreme conditions.

(a) Cr is more active than H2. This means that it can displace hydrogen under the

right conditions. However, Cr is not active enough to displace hydrogen in

cold water. Either hydrochloric acid solution or steam is required to cause a

reaction. Chromium forms a 2+ ion in the activity series.

Cr reacts with HCl: Cr(s) + 2HCl(aq) ¡ú CrCl2(aq) + H2(g)

Cr reacts with steam: Cr(s) + 2H2O(g) ----> Cr(OH)2(s) + H2(g)

In a single-displacement reaction, 1 element displaces its ionic counterpart from a

compound. That is, a metal displaces the metal ion, or a nonmetal displaces the

nonmetal ion. To determine whether a reaction occurs, we compare the activities

of the metals involved (Figure 5.21). If the metal is more active than the metal

whose ion appears in the compound, a reaction occurs. In these cases, the formula

for the ionic product is determined by the metal ion that is produced. If you can¡¯t

predict the charge (i.e. it is not listed in Figure 3.12), assume that it has a charge

of 2+. For example if Fe displaces Cu, Fe will form a 2+ ion. In this type of

single-displacement reaction, the formula for the anion remains unchanged.

(a) Al (s) higher on the activity series than Cu so a reaction occurs. Al forms a 3+

ion, and Cu2+ is displaced as copper metal, Cu(s).

2Al(s) + 3CuSO4(aq) ¡ú Al2(SO4)3(aq) + 3Cu(s)

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(b) Cs is higher in activity than H2 so a reaction occurs. In reactions of active

metals with water, hydrogen gas is formed. Cs forms a 1+ ion, and H+ is

displaced as H2(g). When metals displace H+ from H2O (or HOH), the

product is a metal hydroxide.

2Cs(s) + 2H2O(l) ¡ú 2CsOH(aq) + H2(g)

13.

In a single displacement reaction, 1 element displaces its ionic counterpart from a

compound. That is, a metal displaces the metal ion, or a nonmetal displaces the

nonmetal ion. To determine whether a reaction occurs, we compare the activities

of the metals involved (Figure 5.21). If the metal is more active than the metal

whose ion appears in the compound, a reaction occurs.

(a) Nickel is less active than iron. No reaction occurs.

(b) Aluminum is more active than nickel. The reaction occurs.

(c) Iron is more active than copper. The reaction occurs.

(d) Tin is less active than aluminum. No reaction occurs

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