CHEMICAL Equations WORD EQUATION Potassium metal Reactants are

CHEMICAL Equations

WORD EQUATION Potassium metal Reactants are on the left-hand side of the equation + oxygen gas + sign means “reacts with” Symbolic Equation potassium oxide Products are on the right-hand side of the equation Arrow means produces/yields/ makes 4 K(s) + O 2(g) 2 K 2 O(s) STATE OF MATTER - Letters indicate the state of each compound. COEFFICIENTS (aq) = aqueous/dissolved in water - Indicates how many of each molecule there is. (s) = solid -i. e. : there are 4 molecules of K ( l ) = liquid (g) = gas

Conservation of Mass - total mass of the products is always equal to the total mass of the reactant

Balancing Equations 4 K + O 2 2 K 2 O • Law of conservation of mass says you must have equal number of atoms on the reactant side as there is on the product side. • Compare reactants with products, which atoms are unbalanced? ? • Note: If there is no number as a coefficient than it is 1 • You can only change the coefficients (in front of each substance) and not subscripts behind!

TIPS for Balancing Equations • Balance chemical equations tips – Count all atoms & recount each time – Polyatomic ions (such as SO 42–) can often be balanced as a whole group – Balance the H’s 2 nd last – Balance O’s Last – Always double-check after you think you are finished!

Balancing Equations 3 Li + Al. Cl 3 Al + 3 Li. Cl 1 Lithium, 1 Aluminum 3 Chlorine 1 Lithium, 1 Aluminum 1 Chlorine Recount: 1 Lithium, 1 Aluminum 3 Chlorine 3 Lithium, 1 Aluminum 3 Chlorine Recount: 3 Lithium, 1 Aluminum 3 Chlorine

Balancing Equations CH 4(g) + 2 O 2 (g) 2 H 2 O(aq ) + CO 2(g) 1 Carbon, 4 Hydrogen, 2 Oxygen 1 Carbon, 2 Hydrogen, 3 Oxygen – do O last and H 2 nd last. Recount: 1 Carbon, 4 Hydrogen, 2 Oxygen 1 Carbon, 4 Hydrogen, 4 Oxygen Recount: 1 Carbon, 4 Hydrogen, 4 Oxygen

Balancing Equations H 2 SO 4 + 2 Na. F Na 2 SO 4 + 2 HF 2 H, 1 SO 4 1 Na, 1 F 2 Na, 1 SO 4, 1 H, 1 F 2 H, 1 SO 4 2 Na, 2 F 2 Na, 1 SO 4, 2 H, 2 F

Balance the following: 2 Fe 3 Sn(NO 2)4 2 C 2 H 6 + + + 3 Br 2 2 Fe. Br 3 4 K 3 PO 4 12 KNO 2 7 O 2 4 CO 2 + Sn 3(PO 4)4 + 6 H 2 O

Turn Word Equations into Balanced Equations Example #1: Word Equation: Solutions of lead (II) nitrate react with potassium iodide to produce solid lead (II) iodide and a solution of potassium nitrate. Skeleton Equation: Pb(NO 3)2(aq) + KI(aq) Pb. I 2(s) + KNO 3(aq) Balanced Equation: Pb(NO 3)2(aq) + 2 KI(aq) Pb. I 2(s) + 2 KNO 3(aq) Example #2: Word Equation: Copper reacts with hydrogen nitrate to produce copper (II) nitrate plus hydrogen. Skeleton Equation: Cu + H(NO 3) Balanced Equation: Cu + 2 H(NO 3) Cu(NO 3)2 + H 2