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Chemical Reactions. Standards. Conservation of Matter and Stoichiometry 3a. Students know how to describe chemical reactions by writing balanced equations. Objectives. Identifying the reactants, products and other parts of chemical equations
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Standards • Conservation of Matter and Stoichiometry 3a. Students know how to describe chemical reactions by writing balanced equations
Objectives • Identifying the reactants, products and other parts of chemical equations • Write word equations from a chemical reaction description • Write chemical equations from word equations • Identify and include solid (s), liquid (l), gas (s), and/or aqueous (aq) in chemical equations • Identify and write the seven diatomic elements
Definitions • Chemical equation: a precise detailed accounting of both the identities and amounts of reactants consumed and products formed in a reaction • Identities: all participants in reaction get named • Amounts: how much is specified in equation, (moles) • Reactants: the starting substance(s) in a chemical reaction • Product: substance(s) formed in a chemical reaction
Definitions • Word equation: description of a reaction without using chemical formulas • Reactants: what you start with • Products: what is made
Definitions • Catalyst: a substance that speeds up a reaction without being used up; enzymes good example • Aqueous: dissolved in water (aq) • Diatomic: two of the same atom naturally bound together
Product Reactants Writing a Word Equation • Hydrogen reacts with oxygen to form water • Word Equation: • hydrogen + oxygen → water • Chemical Equation: • H2 + O2 →H2O
Diatomic Elements • Diatomic: two of the same atom naturally bound together • Hydrogen and Oxygen and some others exist bound together. They are always found as a pair, so when you write them write them as H2, O2.
Write the Word & Chemical Equation… • Calcium metal reacts with chlorine gas to produce calcium chloride • Calcium + chlorine → calcium chloride • Ca + Cl2 → CaCl2
Write the Word & Chemical Equation… • When zinc metal reacts with oxygen gas, solid zinc oxide is formed. • Zinc + oxygen → zinc oxide • Zn + O2 → ZnO
Write the Word and Chemical Equation… • Carbon dioxide gas and water are produced when methane gas is burned in oxygen. • Methane + oxygen → carbon dioxide + water • CH4 + O2 → CO2 + H20
Write the Word & Chemical Equation… • When zinc metal is placed in a solution of hydrochloric acid, hydrogen gas and a zinc chloride solution are formed. • Zinc + hydrochloric acid → hydrogen gas + zinc chloride • Zn(s) + HCl (aq) → H2 (g) + ZnCl2 (aq)
Rules for balancing • Must have same # of each atom on both sides of the equation • Must use coefficients to balance, can not add subscripts
Balance the Equation • Calcium metal reacts with chlorine gas to produce calcium chloride • Calcium + chlorine → calcium chloride • Ca + Cl2 → CaCl2
Balance the Equation • When zinc metal reacts with oxygen gas, solid zinc oxide is formed. • Zinc + oxygen → zinc oxide • Zn + O2 → ZnO
Balance the Equation • Carbon dioxide gas and water are produced when methane gas is burned in oxygen. • Methane + oxygen → carbon dioxide + water • CH4 + O2 → CO2 + H20
Balance the Equation • When zinc metal is placed in a solution of hydrochloric acid, hydrogen gas and a zinc chloride solution are formed. • Zinc + hydrochloric acid → hydrogen gas + zinc chloride • Zn(s) + HCl (aq) → H2 (g) + ZnCl2 (aq)