Chapter 11: Chemical Reactions Describing Chemical Reactions

Learning Targets You will identify if a chemical reaction has occurred. You will write a balanced chemical equation from a chemical reaction sentence or word problem.

Signs of a Chemical Reaction Color change A solid forms (precipitate) Bubbles form (gas is being produced) Heat and/or a flame is produced, or heat is absorbed Notice with all of these, something new is being formed You will identify if a chemical reaction has occurred.

Word Equations Reactants  Products Must have correct formulas! Remember diatomic molecules (H 2, N 2, O 2, F 2, Cl 2, Br 2, I 2 ) You will write a balanced chemical equation from a chemical reaction sentence or word problem.

Word Equations Examples Write a skeleton equation for the following: 1. When solid sodium is dropped in water, hydrogen gas and aqueous sodium hydroxide are produced. 2. Sulfur burns in oxygen to form sulfur dioxide. You will write a balanced chemical equation from a chemical reaction sentence or word problem.

Word Equations Answers 1. When solid sodium is dropped in water, hydrogen gas and aqueous sodium hydroxide are produced. Na (s) + H 2 O (l)  NaOH (aq) + H 2 (g) 2. Sulfur burns in oxygen to form sulfur dioxide. S + O 2  SO 2 You will write a balanced chemical equation from a chemical reaction sentence or word problem.

Try on your own Write the chemical equation for each of the following reactions. Solid mercury (II) oxide decomposes to produce liquid mercury metal and gaseous oxygen. Solid carbon reacts with gaseous oxygen to form gaseous carbon dioxide. HgO (s)  Hg (l) + O 2 (g) C (s) + O 2 (g)  CO 2 (g) You will write a balanced chemical equation from a chemical reaction sentence or word problem.

Balancing Chemical Equations MUST balance equations to satisfy Law of Conservation of Mass –Atoms are neither created or destroyed in chemical reactions, only regrouped or rearranged. # of atoms entering a reaction must = # of atoms exiting the reaction. You will write a balanced chemical equation from a chemical reaction sentence or word problem.

Balancing Chemical Equations Balance w/coefficients Simplest whole number ratio Coefficients represent the # of moles or molecules of the substance it corresponds with. Should be in front and only in front of compounds or elements in chemical equation. You will write a balanced chemical equation from a chemical reaction sentence or word problem.

Balancing Chemical Equations An incorrect balanced chemical equation would look like the following: _ H 2 (g) + _ O 2 (g)  _ H 2 2O (l) A correct balanced chemical equation would look like the following: 2 H 2 (g) + _ O 2 (g)  2 H 2 O (l) *put blanks in front of each element, molecule or compound to help with this You will write a balanced chemical equation from a chemical reaction sentence or word problem.

Balancing Chemical Equations No one solid way to balancing chemical equations. Some may: balance by sight follow a strict order make a table but whatever the method, # of atoms going into the equation should = # of atoms going out of the equation. You will write a balanced chemical equation from a chemical reaction sentence or word problem.

Balancing Chemical Equations You will write a balanced chemical equation from a chemical reaction sentence or word problem.

Balancing Chemical Equations 1. _ NaHCO 3 (s) + _ HCl (aq)  _ NaCl (aq) + _ H 2 O (l) + _ CO 2 (g) 2. _ AgNO 3 (aq) + _ Cu (s)  _ Cu(NO 3 ) 2 (aq) + Ag (s) 3. _ Al (s) + O 2 (g)  _ Al 2 O 3 (s)

Balancing Chemical Equations Examples 1. Balance the equation: _ CO + _ Fe 2 O 3  _ Fe + _ CO 2 2. Write the balanced chemical equation for the reaction of carbon with oxygen to form carbon monoxide. You will write a balanced chemical equation from a chemical reaction sentence or word problem.

Balancing Chemical Equations Answers 1. Balance the equation: 3 CO + _ Fe 2 O 3  2 Fe + 3 CO 2 2. Write the balanced chemical equation for the reaction of carbon with oxygen to form carbon monoxide. 2 C + _ O 2  2 CO You will write a balanced chemical equation from a chemical reaction sentence or word problem.

Try on your own Identify the reactants and products and write the unbalanced equation (including symbols for states) for each of the following chemical reactions. Solid magnesium metal reacts with liquid water to form solid magnesium hydroxide and hydrogen gas. Gaseous ammonia reacts with gaseous oxygen to form gaseous nitrogen monoxide and gaseous water. Mg (s) + H 2 O (l)  Mg(OH) 2 (s) + H 2 (g) NH 3 (g) + O 2 (g)  NO (g) + H 2 O (g) You will learn the signs of and how to write balanced equations for chemical reactions.

Examples Write the balanced chemical equation for each of the following reactions. Nitrogen monoxide gas reacts with hydrogen gas to form nitrogen gas and liquid water. Lithium metal reacts with chlorine gas to form solid lithium chloride. 2 NO (g) + 2 H 2 (g)  N 2 (g) + 2 H 2 O (l) 2 Li (s) + Cl 2 (g)  2 LiCl (s) You will learn the signs of and how to write balanced equations for chemical reactions.

Balancing Chemical Equations - Try on your own Write the balanced chemical equation for each of the following reactions. Iron metal reacts with oxygen gas in the air to form solid iron (III) oxide. Solid diboron trioxide reacts with liquid water to form boric acid, B(OH) 3. 4 Fe (s) + 3 O 2 (g)  2 Fe 2 O 3 (s) _ B 2 O 3 (s) + 3 H 2 O (l)  2 B(OH) 3 (aq) You will write a balanced chemical equation from a chemical reaction sentence or word problem.

Examples Page , 12, 16, 18, 20, 28, blue letters only You will learn the signs of and how to write balanced equations for chemical reactions.