Types of Reactions

(1) Single displacement - a reaction in which one element displaces another in a compound.

M1 + MNm --- M + M1Nm Nm1 + MNm -- Nm + MNm1 element + compound --- element + compound

The element, which displaces another in a compound, must be more active (reactive) than the one it is replacing.

In order to determine if the reaction will take place, you must consult an activity series.

There are separate lists for metals and nonmetals. Examples:

Cl2 + 2 KBr -- KCl + Br2 Ca + Mg2O -- CaO + 2 Mg Li2O + Na -- no rxn

(2) Double displacement – a reaction in which the positive and negative portions of two compounds are interchanged.

MNm + M1Nm1 --- MNm1 + M1Nm compound + compound -- compound + compound

Examples: PbCl2 + Li2SO4 --- 2 LiCl + PbSO4 ZnBr2 + 2 AgNO3 -- Zn(NO3)2 + 2 AgBr BaCl2 + KIO3 -- Ba(IO3)2 + 2 KCl

NOTE: When writing the formula for a compound the ions must have an opposite charge and the sum of the charges must equal zero. (3) Decomposition – a reaction where a substance breaks into simpler substances when energy is applied.

A -- B + C + D

compound -- elements or compounds

There are decomposition patterns that must be followed to correctly predict the products of a decomposition reaction. Decomposition Patterns

MNm -- M + Nm NH4NmO -- NH3 + HNmO NH4Nm -- NH3 + HNm * NH4NO3 -- H2O + N2O * NH4NO2 -- H2O + N2 MSO4 -- MO + SO2 + O2 MSO3 -- MO + SO2 MPO4 -- MO + P2O5 MPO3 -- MO + P2O3 MCO3 -- MO + CO2 MSiO3 -- MO + SiO2 MAsO4 -- MO + As2O5 MClO3 -- MCl + O2 MOH -- MO + H2O MNO3 -- MO + NO2 + O2 * KNO3 -- KNO2 + O2 * NaNO3 -- NaNO2 + O2

* = exception Examples:

CdCO3 -- CdO + CO2 Pb(OH)2 -- PbO + H2O

(4) Synthesis – a reaction in which two or more substance combine to form one new substance.

B + C + D -- A element or + element or -- compound compound compound

Synthesis patterns are the reverse of decomposition patterns.

Example: MO + H2O -- MOH M + Nm -- MNm

When writing a formula, do not forget that the overall charge on a compound must equal zero (be sure to consider subscripts). Examples: NH3 + HCl -- NH4Cl CaO + SiO2 -- CaSiO3 2 H2 + O2 -- 2 H2O

Substitute symbols for names, predict the products, and balance.

(1) copper (II) carbonate -- CuCO3(s) -- CuO(s) + CO2(g) (decomposition)

(2) copper (I) + sulfur -- 2 Cu(s) + S(s) -- Cu2S(s) (synthesis)

(3) silver nitrate + sulfuric acid -- 2 AgNO3(aq) + H2SO4(aq) -- Ag2SO4(s) + 2 HNO3 (double displacement) Practice the following:

(1) sulfuric acid -- (2) chromium(II) + hydrochloric acid -- (3) ammonium nitrate -- (4) sodium + oxygen -- (5) calcium hydroxide + sulfuric acid -- (6) copper(II) + silver nitrate --

Solutions to practice:

(1) sulfuric acid -- 2 H2SO4(aq) -- 2 H2O(l) + 2 SO2(g) + O2(g)

(2) chromium(II) + hydrochloric acid -- Cr(s) + 2 HCl(l) -- CrCl2(aq) + H2(g)

(3) ammonium nitrate -- NH4NO3(s) -- 2 H2O(l) + N2O(g)

(4) sodium + oxygen -- 4 Na(s) + O2(g) -- 2 Na2O(s) (5) calcium hydroxide + sulfuric acid -- Ca(OH)2(aq) + H2SO4(aq) -- CaSO4(s) + 2 H2O(l)

(6) copper(II) + silver nitrate -- Cu(s) + 2 AgNO3(aq) -- 2 Ag(s) + Cu(NO3)2(aq) Mass – Mass Relationships

Problem: How much reactant is needed to react with a specific amount of another reactant? How much product can be expected from a specific mass of reactant?

We use balanced equations to solve problems involving a chemical reaction. Calculations such as these are called mass-mass problems.

Mass-mass problems involve finding the mass of one substance from the given mass of another substance.

Example: How many grams of silver chloride can be produced from the reaction of 17.0 g of silver nitrate with excess sodium chloride?

(1) Write an equation and balance. AgNO3(aq) + NaCl(aq) --AgCl(s) + NaNO3(aq) 17.0 g (2) Find the number of moles of the given substance and the required substance.

(3) Use the balanced equation to determine the ratio of the moles or required substance to moles of a given substance.

NOTE: The coefficients in a balanced equation indicate the number of moles of reactants used and products produced in a chemical reaction.

(4) Express the moles of required substance in terms of grams. Example: How many grams of Cu2S could be produced from 9.9 g of CuCl reacting with an excess of H2S gas?

Example: How many grams of calcium hydroxide will be needed to react completely with 10 grams of phosphoric acid? Mass-Mass Problems

(1) Given the following equation:

2 KClO3 -- 2 KCl + 3 O2

How many moles of O2 can be produced by letting 12.00 moles of KClO3 react?

(2) Given the equation:

2 K + Cl2 -- 2 KCl

How many grams of KCl are produced from 2.50 g of K and excess Cl2? From 1.00 g and excess K? (3) Given the equation:

Na2O + H2O -- 2 NaOH

How many grams of NaOH are produced 2 from 1.20 x 10 grams of Na2O? How many grams of Na2O are required to produce 1.60 x 102 grams of NaOH?

(4) Given the following equation:

Cu + 2 AgNO3 -- Cu(NO3)2 + 2 Ag

How many moles of Cu are needed to react with 3.50 moles of AgNO3? If 89.5 g of Ag were produced, how many grams of Cu reacted?