1. Challenge Stoichiometry Lesson 7

2. A 10.0 g sample of a Cu/Ag alloy reacted with concentrated HNO 3 according to the following equations. A total of 8.986 g of NO 2 was isolated. Assuming a 100 % yield of NO 2, determine the mass of Cu and Ag in the alloy. Cu (s) + 4HNO 3(aq) → Cu(NO 3 ) 2(aq) + 2NO 2(g) + 2H 2 O (l) Ω g?g 2Ag (s) + 4HNO 3(aq) → 2AgNO 3(aq) + 2NO 2(g) + 2H 2 O (l) (10 - Ω) g?g 10.0 g8.986 g

3. A 10.0 g sample of a Cu/Ag alloy reacted with concentrated HNO 3 according to the following equations. A total of 8.986 g of NO 2 was isolated. Assuming a 100 % yield of NO 2, determine the mass of Cu and Ag in the alloy. Cu (s) + 4HNO 3(aq) → Cu(NO 3 ) 2(aq) + 2NO 2(g) + 2H 2 O (l) 2Ag (s) + 4HNO 3(aq) → 2AgNO 3(aq) + 2NO 2(g) + 2H 2 O (l) = 1.4488 Ωx 46.0 g 1 mole x 2 mole NO 2 1 mole Cu x 1 mole 63.5 g Ω g Cu = 4.2632 - 0.42632 Ω 1 mole x 46.0 g 2 mole Ag x 2 mole NO 2 107.9 g x 1 mole10 – Ω g Ag 1.4488 Ω + 4.2632 - 0.42632 Ω = 8.986 1.0225 Ω =4.7228 10.0 - 4.62 = 5.4 g Ag Ω =4.62 g Cu Note the loss of a sig fig!

4. A 10.00 g sample of brass, a Cu/Zn alloy, is completely reacted with concentrated HNO 3 according to the following equations. A total of 14.2356 g of NO 2 was isolated. Assuming a 100 % yield of NO 2, determine the mass of Cu and Zn in the alloy. Cu (s) + 4HNO 3(aq) → Cu(NO 3 ) 2(aq) + 2NO 2(g) + 2H 2 O (l) Ω g?g Zn (s) + 4HNO 3(aq) → Zn(NO 3 ) 2(aq) + 2NO 2(g) + 2H 2 O (l) (10 - Ω) g?g 10.0 g14.2356 g

5. A 10.00 g sample of brass, a Cu/Zn alloy, is completely reacted with concentrated HNO 3 according to the following equations. A total of 14.2356 g of NO 2 was isolated. Assuming a 100 % yield of NO 2, determine the mass of Cu and Zn in the alloy. Cu (s) + 4HNO 3(aq) → Cu(NO 3 ) 2(aq) + 2NO 2(g) + 2H 2 O (l) Zn (s) + 4HNO 3(aq) → Zn(NO 3 ) 2(aq) + 2NO 2(g) + 2H 2 O (l) = 1.4488 Ωx 46.0 g 1 mole x 2 mole NO 2 1 mole Cu x 1 mole 63.5 g Ω g Cu = 14.0673 - 1.40673 Ω 1 mole x 46.0 g 1 mole Zn x 2 mole NO 2 65.4 g x 1 mole10 – Ω g Zn 1.4488 Ω + 14.0673 - 1.40673 Ω = 14.2356 0.04207 Ω =0.1683 10.00 – 4.00 = 6.00 g Zn Ω = 4.00 g Cu