1. Welcome! Wednesday 9/26 Get out a sheet of paper for the warm up

2. Write the skeleton reaction for the following: (leave room between each question) 1. Hydrogen gas plus oxygen gas yields liquid water 2. Solid mercury II oxide yields mercury metal and oxygen gas 3. Solid iron II oxide plus hydrogen gas yields iron metal plus liquid water 4. Chlorine gas plus sodium metal yields solid sodium chloride plus heat

3. Balancing chemical equations Example: Magnesium plus oxygen yields magesium oxide 1. Write out the balanced formulas for the reactants and the products (reactants on the left of the arrow, products on the right). Include states of matter, if given. –Mg (s) + O 2 (g) MgO 2. Law of Conservation of Mass tells us what goes into a reaction must come out of the reaction: start counting atoms on each side –1 mol Mg, 2 mol O 1 mol Mg, 1 mol O

4. 3. Use coefficients to balance 2Mg + O 2 2 MgO Dont change subscripts once the formulas are written Look for polyatomics on both sides

5. Note: Coefficients are MULTIPLIED by a subscript 2 O 2 = 4 oxygen atoms

6. Heat may be a reactant or a product It is symbolized by Δ Catalysts are symbolized above the arrow

7. Balance 1. H 2 (g) + O 2 (g) H 2 O (l) 2. HgO (s) Hg (s)+ O 2 (g) 3. FeO (s) + H 2 (g) Fe (s) + H 2 O (l) 4. Cl 2 (g) + Na (s) NaCl (s) + Δ (heat)

8. 1.2 H 2 (g)+ O 2 (g) 2 H 2 O (l) 2.2 HgO (s) 2Hg (s) + O 2 (g) 3.Already balanced! 4.Cl 2 (g) + 2Na (s) 2 NaCl (s) + Δ (heat)