Law of Conservation of Mass Matter cannot be created or destroyed in an ordinary chemical reaction. ReactantsProducts 4Fe + 3O 2 → 2Fe 2 O 3 100g + 50g = 150g

To balance an equation take an “atom inventory” on both sides of the equation: ___K + ___H 2 O  ___KOH + ___H 2 ReactantsProducts K:1K:1 H:2H:3 O:1O:1

Next choose coefficients to balance the equation: _2_K + _2_H 2 O  _2_KOH + _1_H 2 ReactantsProducts K:12K:12 H:24H:34 O:12O:12

Practice Problems: (All practice problems are from TEA released TAKS Tests) 1. What are the coefficients that will balance this chemical equation? A 2, 1, 1 B 3, 4, 2 C 2, 2, 1 D 4, 3, 2

2. The chemical equation shows CaCO 3 being heated. Which of these statements best describes the mass of the products if 100 g of CaCO 3 is heated? A The difference in the products’ masses is equal to the mass of the CaCO 3. B The sum of the products’ masses is less than the mass of the CaCO 3. C The mass of each product is equal to the mass of the CaCO 3. D The sum of the products’ masses equals the mass of the CaCO 3. (All practice problems are from TEA released TAKS Tests)

3. Which chemical equation supports the law of conservation of mass? F 2H 2 O(l) → H 2 (g) + O 2 (g) G Zn(s) + HCl(aq) → ZnCl 2 (aq) + H 2 (g) H Al 4 C 3 (s) + H 2 O(l) → CH 4 (g) + Al(OH) 3 (s) J CH 4 (g) + 2O 2 (g) → CO 2 (g) + 2H 2 O(g) (All practice problems are from TEA released TAKS Tests)

4. When 127 g of copper reacts with 32 g of oxygen gas to form copper (II) oxide, no copper or oxygen is left over. How much copper (II) oxide is produced? F 32 g G 95 g H 127 g J 159 g (All practice problems are from TEA released TAKS Tests)

5. When the above equation is balanced, the coefficient for magnesium chloride is — A 0 B 1 C 2 D 4 (All practice problems are from TEA released TAKS Tests)

6. According to the law of conservation of mass, how much zinc was present in the zinc carbonate? A 40 g B 88 g C 104 g D 256 g (All practice problems are from TEA released TAKS Tests)

7. According to this information, what is the chemical formula for aluminum sulfate? A AlSO 4 B Al 2 (SO 4 ) 3 C Al 3 (SO 4 ) 2 D Al 6 SO 4 (All practice problems are from TEA released TAKS Tests)

8. The chemical formula for calcium chloride is — F Ca 2 Cl G CaCl H CaCl 2 J Ca 2 Cl 3 (All practice problems are from TEA released TAKS Tests)

9.In the procedure shown above, a calcium chloride solution is mixed with a sodium sulfate solution to create the products shown. Which of the following is illustrated by this activity? (A) The law of conservation of mass (B) The theory of thermal equilibrium (C) The law of conservation of momentum (D) The theory of covalent bonding

__Ca(C 2 H 3 O 2 ) 2 + __K 3 PO 4 → __Ca 3 (PO 4 ) 2 + __KC 2 H 3 O Which set of coefficients balances the equation above? (F) 3, 3, 1, 2 (G) 6, 1, 1, 3 (H) 3, 2, 1, 6 (J) 6, 2, 1, 6