Chapter 7 - Chemical Reactions and Quantities - 7.8 Limiting Reactants and Percent Yield - Questions and Problems - Page 270: 7.74

a. 15 clocks b. 4 clocks

a. Knowing that each clock requires one face and two hands: 1 clock: 1 clock face and 2 hands. 2 clocks: 2 clock faces and 4 hands. 3 clocks: 3 clock faces and 6 hands. . . . 15 clocks: 15 clock faces and 30 hands. 16 clocks: 16 clock faces and 32 hands. As we can see, in order to make 16 clocks, there will need to be 16 clock faces. But, the clock maker can make 15 clocks, because he has sufficient material (15 clock faces and 30 hands). b. Knowing that each clock requires one face and two hands, these are the numbers of faces and hands required for some numbers of watches: 1 clock: 1 clock face and 2 hands. 2 clocks: 2 clock faces and 4 hands. 3 clocks: 3 clock faces and 6 hands. 4 clocks: 4 clock faces and 8 hands. 5 clocks: 5 clock faces and 10 hands. As we can see, in order to make 5 clocks, there will need to be 10 hands, which are not available. But, the clock maker can make 4 clocks, because he has sufficient material (4 clock faces and 8 hands).