Lecture 11.1- Balancing Equations
- 1. Describing Chemical Reactions On May 6, 1937, the huge airship Hindenburg erupted into a fireball. Within a short time, 210,000 cubic meters of hydrogen had burned and the airship was destroyed. The chemical reaction that occurred is “hydrogen combines with oxygen to produce water.”
- 2. Basic chemical equation format Reactants Products yields
- 3. Word Equations use chemical names bleach + ammonia poisonous gas
- 4. write the formulas of the reactants to the left of the yields sign (arrow) and the formulas of the products to the right. To write a chemical equation H2 + O2 H2O Reactants Product
- 5. An unbalanced(skeleton) equation does not indicate the relative amounts of the reactants and products. Here is the unbalanced equation for rusting: Fe + O2 Fe2O3 Why is it unbalanced?
- 6. Methane + Oxygen Carbon dioxide + Water CH4 + O2 CO2 + H2O
- 7. A catalyst is a substance that speeds up the reaction but is not used up in the reaction. Without Catalyst With Catalyst
- 8. Special conditions, including use of a catalyst, are written above the arrow H2O2 H2O + O2 KI
- 10. Complete chemical equations show the state of matter (in parenthesis) after each formula. NaCl (s ) H2O (l ) O2 (g )
- 11. iron + oxygen → iron(III) oxide Fe(s) + O2(g) Fe2O3(s)
- 12. Hydrogen Peroxide Water and Oxygen H2O2(aq) H2O(l) + O2(g)
- 16. Chemical equations are not complete unless they are BALANCED.
- 17. To write a balanced equation add the coefficients that will show the reaction obeying the law of conservation of mass. PRODUCTSREACTANTS
- 18. Coefficients are small whole numbers that are placed in front of the formulas in an equation in order to balance it. subscripts coefficient 2H2 + O2 2H2O NEVER change subscripts
- 20. In a balanced equation each side of the equation has the same number of atoms of each element and mass is conserved.
- 30. 1. Propane gas reacts with oxygen to produce water vapor and carbon dioxide. Choose the correct word equation for this reaction. a. propane + carbon dioxide → water + oxygen b. propane + oxygen + water → carbon dioxide c. propane + oxygen + water + carbon dioxide d. propane + oxygen → water + carbon dioxide
- 31. 2. What coefficient for H2SO4 is required to balance the following equation? Ca3(PO4)2 + ____ H2SO4 → 3CaSO4 + 2H3PO4 a. 1 b. 2 c. 3 d. 4
Editor's Notes
- #7: Three common chemical reactions are shown. a) When methane gas burns, it combines with oxygen to form carbon dioxide and water. b) Iron turns to red-brown rust (iron(III) oxide) in the presence of oxygen in the air. c) Hydrogen peroxide decomposes to water and oxygen when used as an antiseptic.
- #8: Hydrogen peroxide decomposes to form water and oxygen gas. a) Bubbles of oxygen appear slowly as decomposition proceeds. b) With the addition of the catalyst manganese(IV) oxide (MnO2), decomposition speeds up. The white “smoke” is condensed water vapor.
- #12: Three common chemical reactions are shown. a) When methane gas burns, it combines with oxygen to form carbon dioxide and water. b) Iron turns to red-brown rust (iron(III) oxide) in the presence of oxygen in the air. c) Hydrogen peroxide decomposes to water and oxygen when used as an antiseptic.
- #13: Three common chemical reactions are shown. a) When methane gas burns, it combines with oxygen to form carbon dioxide and water. b) Iron turns to red-brown rust (iron(III) oxide) in the presence of oxygen in the air. c) Hydrogen peroxide decomposes to water and oxygen when used as an antiseptic.
- #30: Conceptual Problem 11-3