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Balancing Practice Multiple Choice Identify the choice that best completes the statement or answers the question. ____ 1. The principle underpinning the methods for balancing chemical reaction equations is: a. conservation of mass c. creation of atoms b. conservation of charge d. destruction of atoms ____ 2. What does a triangle on the right side of a chemical equation indicate a. Heat is produced c. Heat is absorbed in the reaction b. Heat is necessary to start the d. Potential energy associated with the reaction chemical bonds is increased ____ 3. An endothermic reaction feels a. Hot b. cold c. can’t tell d. rough and bumpy ____ 4. An exothermic reaction will feel a. Hot b. Cold c. can’t tell d. smooth ____ 5. What does the arrow in a chemical reaction equation mean? a. it separates reactants from c. stop products, “yields” b. “equals” d. wrong way ____ 6. What does a double sided arrow in a chemical reaction equation mean? a. The reaction is reversible c. The reaction requires a catalyst b. The reaction doesn’t happen d. The reaction is spontaneous ____ 7. A chemical formula above the arrow indicates: a. A catalyst that will speed up the c. The reaction will not procede if the reaction without being consumed chemical is present b. an element that appears out of thin d. The chemical is consumed in the air reaction ____ 8. How does a catalyst work? a. By lowering the activation energy b. By raising the activation energy c. decreasing the temperature d. absorbing excess heat ____ 9. What does a letter subscript in parenthesis after a reactant or product indicate? a. The physical state of matter c. the amount of reactant/product b. the mass or volume of the reactant/product needed/produced d. the intials of the guy who discovered the reactant/product ____ 10. Coefficients indicate the number of formula units, or moles needed for a balanced reaction. Where do they appear? a. above and left of the element c. Infront of, the same size and in line symbol with, the reactant/product symbol/formula b. below and right of the element d. infront and below the formula symbol Matching a. synthesis b. single replacement c. double replacement d. decomposition e. combustion f. neutralizatoin ____ 11. AB + CD --> AD + CB ____ 12. A + B --> C ____ 13. A --> B + C ____ 14. A + BC --> AC + B ____ 15. CxHy + O2 --> CO2 + H2O ____ 16. HxB + A(OH)y --> AB + water Short Answer 17. Name the product and balance the reaction: ___Ta + ___O2 --> ___ ________ ? Name of product________ 18. Balance and identify the type of reaction: ____2NaI --> ____2Na + ____I2? type ________ 19. Balance and identify the type of reaction. __FeS + __F2 --> __FeF2 + __S type ________ 20. Balance the reaction equation, and identify the ype of reaction. ___H2CrO4 + ___Os(OH)4 --Os(CrO4)2 + ___H2O type ________ ec__________________________ name the salt produced above Balancing Practice Answer Section MULTIPLE CHOICE 1. ANS: A Just is... PTS: 1 2. ANS: A right side is products Potential energy is stored in chemical bonds. If the reaction gives off heat (feels hot) then the energy stored in the bonds is decreasing. The product bonds store less energy than the reactant bonds. PTS: 1 3. ANS: B Endo thermic absorbs heat so it takes it from the surrounding, including the peson touching it, so it feels cold. PTS: 1 4. ANS: A Exo meas gives off heat. It will feel warmer than it was before the reaction. PTS: 1 5. ANS: A Yields or products, makes, combine to form etc PTS: 1 6. ANS: A Goes both ways PTS: 1 7. ANS: A Catalyst that will speed up the reaction without being consumed. PTS: 1 8. ANS: A PTS: 1 9. ANS: A (s)olid, (l)iquid, (g)as or (aq) aqueous (water) solution PTS: 1 10. ANS: C in front, same size PTS: 1 MATCHING 11. ANS: C PTS: 1 12. ANS: A PTS: 1 13. ANS: D PTS: 1 14. ANS: B PTS: 1 15. ANS: E PTS: 1 16. ANS: F PTS: 1 SHORT ANSWER 17. ANS: 4Ta + 5O2 --> 2Ta2O5 Tantalum oxide Tantalum; oxide ; 180.948x2 = 361.896 (6 sigfig --> 3 decimal places) 15.9994x5 = 79.997 (6 sigfig --> 4 decimal places) mass=441.8930000 sigfigs 441.893 (min of decimal places = 3) PTS: 1 18. ANS: 2NaI --> 2Na + I2 Sodium iodide Sodium; 22.98977x1 = 22.98977 (7 sigfig --> 5 decimal places) iodide ; 126.905x1 = 126.905 (6 sigfig --> 3 decimal places) mass=149.8947700 sigfigs 149.895 (min of decimal places = 3) PTS: 1 19. ANS: The products will be made by swaping the anions. Write the ions with charges swap charges for subscripts and reduce by gcf. FeF2 + Cs2S greatest common factor of the balanced coefficients is 2 FeS + F2 --> FeF2 + S Amass 87.907 12.85 grams F2 Bmass 37.996806 Cmass 93.843806 32.06 Dmass 1 mole 1 mole S 32.06 grams S 10.842253 grams 37.996806 grams F2 1 mole F2 1 mole PTS: 3 20. ANS: The products will be made by swaping the anions. Write the ions with charges swap charges for subscripts and reduce by gcf. Osmium (IV) hydroxide and Hydrogen chromate Os(CrO4)2 + H2O greatest common factor of the balanced coefficients is 1 2H2CrO4 PTS: 3 + Os(OH)4 --> Os(CrO4)2 + 4H2O