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How to Balance a Chemical Equation

How to Balance a Chemical Equation. 8C investigate and identify the law of conservation of mass. Conservation of Mass. Both the mass and the number of atoms must be equal on both sides of a chemical equation. The Mass of the reactants = the mass of the products

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How to Balance a Chemical Equation

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  1. How to Balance a Chemical Equation 8C investigate and identify the law of conservation of mass.

  2. Conservation of Mass • Both the mass and the number of atoms must be equal on both sides of a chemical equation. • The Mass of the reactants = the mass of the products • Mater can be neither created nor destroyed in a chemical reaction. • If you start with 5 atoms of “O” → • → You must end with 5 atoms of “O” • The total mass on the left side must = the total mass on the right side of the equation.

  3. 1. The mass of a rusty bicycle is found to be slightly greater than the mass of the same bicycle before it rusted. The change in mass indicates that the rusting process — • is a physical change • involves an energy-to-matter conversion • decreases the density of the metal • involves metal bonding with other atoms [Default] [MC Any] [MC All]

  4. 2. The Law of Conservation of Mass states that in a chemical reaction the mass of the reactants must equal the mass of the products. Mg + HCl→ MgCl2 + H2 20 g 20g 35g ?

  5. 2. The Law of Conservation of Mass states that in a chemical reaction the mass of the reactants must equal the mass of the products. Mg + HCl→ MgCl2 + H220 g 20g 35g ? 20 + 20 = 40 → 40 – 35 = 5 40 = 40 Conservation of Mass

  6. 3. The Law of Conservation of Mass states that in a chemical reaction the mass of the reactants must equal the mass of the products. KClO3 KCl + O2 ? g 20g 3g

  7. 3. The Law of Conservation of Mass states that in a chemical reaction the mass of the reactants must equal the mass of the products. KClO3 KCl + O2 ? g 20g 3g23g = 20g + 3 g Conservation of Mass

  8. 4. If all the reactants in a chemical reaction are completely used, which of the following statements accurately describes the relationship between the reactants and the products? • The products must have a different physical state than the reactants. • The total mass of the reactants must equal the total mass of the products. • The reactants must contain more complex molecules than the products do. • The density of the reactants must equal the density of the products. [Default] [MC Any] [MC All]

  9. 5. Which of these would support the idea that mass is conserved in a reaction that produces a gas as a product? • Heating the reactants to ensure the reaction occurs in a gaseous state • Subtracting the mass of the gas from the mass of the solid and liquid products • Mixing the reactants and measuring their total mass • Trapping the gas and measuring its mass [Default] [MC Any] [MC All]

  10. 6. According to the law of conservation of mass, how much zinc was present in the zinc carbonate? • 40 g • 80 g • 104 g • 256 g [Default] [MC Any] [MC All]

  11. 7. The chemical equation shows CaCO3 being heated. Which of these statements best describes the mass of the products if 100 g of CaCO3 is heated? • The difference in the products’ masses is equal to the mass of the CaCO3. • The sum of the products’ masses is less than the mass of the CaCO3. • The mass of each product is equal to the mass of the CaCO3. • The sum of the products’ masses equals the mass of the CaCO3. [Default] [MC Any] [MC All]

  12. 8. 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? • 32 g • 95 g • 127 g • 159 g [Default] [MC Any] [MC All]

  13. 9. In a single-displacement reaction, the chemical change shown above occurs. Whichequation supports the law of conservation of mass? • w = y • x = z • w + x = y + z • w + x = 2(y + z) [Default] [MC Any] [MC All]

  14. 10. Copper (Cu) and sulfur (S) were heated in a covered container. After the reaction was complete, the unreacted sulfur was removed. The table below contains the results of the investigation. How much sulfur, in grams, failed to react with the copper?

  15. 10. Copper (Cu) and sulfur (S) were heated in a covered container. After the reaction was complete, the unreacted sulfur was removed. The table contains the results of the investigation. How much sulfur, in grams, failed to react with the copper? Record and bubble in your answer to the nearest hundredth on the answer document. Cu + S  CuS 3.17+ 2.93 = 6.10 6.10 - 4.78 1.32

  16. Conservation of Mass • The Law of Conservation of Mass states that in a chemical reaction the mass of the reactants must equal the mass of the products. • Notice there is more O2 in the products than in the reactants. So this does not demonstrate the law of conservation of mass. C + H2→ CH4

  17. Conservation of Mass • The Law of Conservation of Mass states that in a chemical reaction the mass of the reactants must equal the mass of the products. • Notice there now is an equal amount of H2 in the products and the reactants. So this equation now demonstrates the law of conservation of mass. C + 2H2→ CH4

  18. 11. Which diagram best demonstrates the law of conservation of mass? • [Option 1] • [Option 2] • [Option 3] • [Option 4] [Default] [MC Any] [MC All]

  19. Reactants Products Diatomic gas Needs more Hydrogen Needs more Oxygen

  20. Reactants Products

  21. Reactants Products Diatomic gas Needs more Hydrogen

  22. Reactants Products Diatomic gas

  23. Reactants Products Needs more Iron Needs more Chlorine Needs more Hydrogen Needs more Hydrogen Needs more Chlorine

  24. Reactants Products

  25. Reactants Products We need more Calcium here. We need more Hydrogen and Phosphate here We need more Chlorine here.

  26. Reactants Products

  27. Reactants Products We need more Ammonium Now we need More Chlorine here

  28. Reactants Products

  29. 12. Aluminum metal and oxygen gas combine to produce aluminum oxide (Al2O3). Which of these is the balanced equation for this reaction? • Al + O2 Al2O3 • 2Al + 2O2 2Al2O3 • 2Al + 3O2 5Al2O3 • 4Al + 3O22Al2O3 [Default] [MC Any] [MC All]

  30. 13. Which chemical equation supports the law of conservation of mass? • 2H2O(l) H2(g) + O2(g) • Zn(s) + HCl(aq)  ZnCl2(aq) + H2(g) • Al4C3(s) + H2O(l) CH4(g) + Al(OH)3(s) • CH4(g) + 2O2(g)CO2(g) + 2H2O(g) [Default] [MC Any] [MC All]

  31. 14. What is the coefficient for H2O when the above equation is balanced? • 1 • 2 • 3 • 4 [Default] [MC Any] [MC All]

  32. 15. Which set of coefficients balances the equation? • 3, 3, 1, 2 • 6, 1, 1, 3 • 3, 2, 1, 6 • 6, 2, 1, 6 [Default] [MC Any] [MC All]

  33. 16. When the above equation is balanced, the coefficient for magnesium chloride is — • 0 • 1 • 2 • 4 [Default] [MC Any] [MC All]

  34. 17. Which additional product balances this reaction? • 4OH(aq) • 4OH(aq) • H2O2(g) • 2H2O(g) [Default] [MC Any] [MC All]

  35. 18. What is the balanced coefficient ratio for the reaction shown above? • 3:3:3:2 • 2:1:2:2 • 2:3:2:2 • 1:1:1:1

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