1. Look at the objectives from Monday and Tuesday. 2. Identify which ones you think you know well, which ones need a little work and which ones need a lot of work. 3. Share your progress with a neighbor.

Conservation of mass and balancing equations

During a chemical reaction mass can not be created or destroyed.

We balance reaction equations to show that we have the same number of each type of atom, both before and after the reaction takes place. Nothing is created, nothing is destroyed. Therefore, the mass stays constant throughout the reaction.

CO 2 One atom of carbon Two atoms of oxygen OR 1 mole of carbon 2 moles of oxygen

3 CO 2 The Coefficient (3) triples the amount of everything… 3 CO 2 = CO 2 + CO 2 + CO 2

3 CO 2 Three atoms of carbon Six atoms of oxygen Or Three moles of carbon Six moles of oxygen

CO 2 Answer: 1 C 2 O 3 CO 2 H 2 O Mg(OH) 2 2 Mg(OH) 2 3 (NH 4 ) 2 CO 3 C 6 H 12 O 6 Mg(C 2 H 3 O 2 ) 2 2 CH 3 CH 2 OH CuCl 2 ● 12 H 2 O Write down each formula and how many atoms (or moles of each element it shows. 3 C 6 O 2 H 1 O 1 Mg 2 O 2 H 2 Mg 4 O 4H 6 N 24 H 3 C 9 O 6 C 12 H 6 O 1 Mg 4 C 6 H 4 O 4 C 12 H 2 O 1 Cu 2Cl 24 H 12 O

NaCl (aq) + AgNO 3 (aq) NaNO 3 (aq) + AgCl (s) 1 Na 1 1 Cl 1 1 Ag 1 1 N 1 3 O 3 This Reaction is already balanced!

H 2 O (l) H 2 (g) + O 2(g) 2 H 2 1 O 2 This Reaction is not balanced! We must add coefficients to balance it

Fe 2 O 3 (s) + CO (g) Fe (s) + CO 2(g) 2 Fe 1 4 O 2 1C 1 This Reaction is not balanced! We must add coefficient to balance it

HCl (aq) + Zn (s)  H 2(g) + ZnCl 2(aq)

H 2 O 2(aq)  O 2(g) + H 2 O (l) MnO 2

H 2(g) + O 2(g)  H 2 O (g)