Balancing Equations and Types of Reactions CHAPTER 9

Word Equations Iron reacts with oxygen to produce iron (III) oxide, or rust. Iron + oxygen iron (III) oxide Reactants are written to the left of the arrow, and products are written to the right. If there are more than one reactant or product, they are separated by a plus sign.

Word Equations How would I write “hydrogen peroxide reacts to form water and oxygen gas”? Hydrogen peroxide water + oxygen

Chemical Equations In a chemical equation, we use the chemical symbols of compounds and elements. Fe + O 2 Fe 2 O 3 This is an example of a skeleton equation, which shows the formulas but does not indicate the relative amounts of reactants and products.

States of Matter You can indicate the physical state of reactants and products by using (s), (l), (g), or (aq) after the chemical formula. H 2 O 2(aq) H 2 O(l) + O 2(g)

States of Matter Aqueous solution: contains one or more substances dissolved in water 1. solute: the substance getting dissolved; what you have less of 2. solvent: the substance doing the dissolving; what you have the most of

Common Symbols Catalysts are used in some reactions to speed up the rate. For example, manganese (IV) oxide, Mn. O 2, can be used as a catalyst to speed up the decomposition of water. Catalysts are written above the arrow. Table 9. 1 in your text lists common symbols used in chemical equations.

Writing Skeleton Equations Write skeleton equations for the following reactions. sulfur burns in oxygen to form sulfur dioxide heating potassium chlorate in the presence of the catalyst manganese (IV) oxide produces oxygen gas. Potassium chloride is left as a solid. KCl. O 3(s) KCl(s) + O 2(g)

Balancing Chemical Equations Word equation for bicycle + wheel + handlebar + pedal bicycle frame Which are products and which are reactants? You might write a chemical formula for the above equation like this… f + w + h + p fw 2 hp 2

Balancing Equations Is this a balanced equation? How does this relate to the Law of Conservation of Mass? In order to balance our equation, we have to put in coefficients. When no coefficient is written, it is assumed to be 1. There must be the same number of atoms of each element.

Rules for Balancing Equations 1. 2. 3. 4. 5. 6. 7. Determine the correct formulas for all the reactants and products. Write the skeleton equation Count the atoms of the elements in the reactants Count the atoms of the elements in the products Change the coefficients to make the number of atoms of each element equal on both sides of the equation (NEVER CHANGE THE SUBSCRIPT!) Write the coefficients in their lowest possible ratio Check your work

Balancing Chemical Equations https: //www. youtube. com/watch? v=y. A 3 TZJ 2 em 6 g

Practice Equations Ag. NO 3 + H 2 S Ag 2 S + HNO 3 Mn. O 2 + HCl Mn. Cl 2 + H 2 O + Cl 2 hydrogen + sulfur hydrogen sulfide iron (III) chloride + calcium hydroxide iron (III) hydroxide + calcium chloride

Classifying Reactions Synthesis, Direct Combination, Combination Reactions: two or more substances combine to form a single substance A + B AB 2 K(s) + Cl 2(g) 2 KCl(s)

Classifying Reactions Decomposition Reactions: a single compound is broken down into two or more products AB A+B Ca. CO 3(s) Ca. O(s) + CO 2(g)

Classifying Reactions Single-Replacement Reactions: atoms of one element replace the atoms of a second element in a compound A + BX AX + B Mg(s) + Zn(NO 3)2(aq) Mg(NO 3)2(aq) + Zn(s) Note: The Activity Series of Metals on p. 293 and the back of your periodic table

Classifying Reactions Double-Replacement Reactions: exchange of positive ions between two reacting compounds…often produce a precipitate, the evolution of gas, or a molecular compound AX + BY AY + BX Na 2 S(aq) + Cd(NO 3)2(aq) Cd. S(s) + 2 Na. NO 3(aq)

Classifying Reactions Combustion Reactions: an element or compound reacts with oxygen, often producing energy as heat and light A + O 2 AO 2 Complete combustion: produces carbon dioxide and water Incomplete combustion: C and CO may also be products CH 4(g) + 2 O 2(g) CO 2(g) + 2 H 2 O(g)

Types of Chemical Reactions https: //www. youtube. com/watch? v=a. MU 1 Ra. Rul. So