Chapter 9 Chemical Reactions Chemical reaction process by

Chapter 9 Chemical Reactions

Chemical reaction process by which the atoms of one or more substances are rearranged to form different substances same as chemical change

Chemical reaction starting substances are reactants substances formed or produced during reaction are products

Evidence of a chemical reaction (change) 1. temperature change 2. color change 3. production of a gas 4. (odor/bubbles) 4. formation of a solid (precipitate)

Chemical equation A statement using chemical formulas to describe the identities and relative amounts of the reactants and products involved in the chemical reaction.

Silver metal reacts with hydrogen sulfide gas in the air to form solid silver sulfide and hydrogen gas.

Some pure elements exist as diatomic molecules. H 2, N 2, O 2, F 2, Cl 2, Br 2, I 2

-gens hydrogen oxygen nitrogen halogens (group 17)

Write formulas / symbols for the following: magnesium nitrogen carbon dioxide fluorine sodium chloride sulfur

Law of Conservation of Mass is neither created nor destroyed during a chemical reaction – it is conserved. Total mass of reactants always equals total mass of products.

Therefore, chemical equations must be balanced; same number of atoms of each element on each side of arrow.

To balance a chemical equation: 1. Count number of atoms of each element on each side of arrow.

2. Add coefficients in front of formulas. Must be lowest whole number ratio.

Iron metal reacts with oxygen gas to form iron(III) oxide (rust. )

Classifying chemical reactions useful for understanding chemical reactions and for predicting products five general types of reactions

Synthesis reactions two or more substances react to form a single product A + B AB Key: one product

Synthesis reaction Zinc metal reacts with solid iodine to form solid zinc iodide.

Decomposition reactions a single compound breaks down into two or more simpler substances (elements or compounds) AB A + B Key: one reactant

Decomposition reactions often must add energy (heat/electricity) to make reaction occur

Decomposition reaction When heated, solid potassium chlorate reacts to form solid potassium chloride and oxygen gas.

Single-replacement reactions one element replaces another element in a compound A + BX AX + B

Single-replacement reactions more active element replaces less active element

When balancing replacement reactions: keep polyatomic ions intact and write water as HOH (hydrogen and a hydroxide. )

Single-replacement reaction Copper metal reacts with aqueous silver nitrate to produce silver metal and aqueous copper(II) nitrate. copper replaces silver

Single-replacement reaction Sodium metal reacts with water to form sodium hydroxide and hydrogen gas.

Double-replacement reactions Exchange of ions between aqueous solutions of two compounds. AX + BY AY + BX

Double-replacement reactions Aqueous solutions of lead(II) nitrate and potassium iodide react to form aqueous potassium nitrate and a precipitate of lead(II) iodide.

Combustion reactions substance reacts rapidly with oxygen gas and releases energy in form of heat and light may also be synthesis reaction

Iron metal reacts with oxygen gas to form iron(III) oxide (rust. )

Iron metal burns in oxygen gas to form iron(III) oxide.

Combustion reactions If reactant contains carbon, then products of a combustion reaction are always carbon dioxide gas and water vapor.

Sucrose (C 12 H 22 O 11) burns in oxygen. Products are carbon dioxide gas and water vapor.

Single-replacement reactions more active element replaces less active element

A more active metal will replace a less active metal. Will the following singlereplacement reaction occur? Fe(s) + Cu(NO 3)2(aq) Yes, iron is more active than copper.

Fe(s) + Cu(NO 3)2(aq) Cu(s) + Fe(NO 3)2(aq)

A more active nonmetal will replace a less active nonmetal. Will the following singlereplacement reaction occur? Cl 2(g) + Na. Br(aq) Yes, chlorine is more active than bromine.