San Jacinto College - CHEM 1311

Chapter 3: Chemical Reactions and Reaction Stoichiometry

1)Convert the following measurements. Show all work, including units that cancel.

1. 1. How many mol of NO2 are in 8.5 × 10²² molecules NO2                                             
   2. How many g of HNO3 are in 0.253 mol HNO3                                                                  
   3. Calculate the number of mole that are in 23.6 g of CaCO3
   4. Calculate the number of mole in 1.4 × 10²⁴ atoms of K                                               

1. 5. How many aluminum atoms are in 16.2 g Al?                                                                  
   6. How many grams of Pb are in 2.55 × 10²³ atoms of lead                                             

1. 7. How many atoms of Na are in 0.120 mol Na                                                    
   8. How many mole of potassium are in 1.25 × 10²¹ atoms K                                          

1. 1. What is the mass of 4.87 × 10²⁴ NO2 molecules?                                                           

j)     How many formula units of NaCl are in 5.0g of NaCl                                    

k) How many O2 molecules are in 0.470 g of oxygen gas                                 

2. How many moles of NaCl result from the complete reaction of 3.4 mol of Cl2?

3. I2 is produced by the reaction of 0.4235 mol of CuCl2 according to the following equation:

What mass of I2 is produced?                                                                           

4. How many gram of O2 can be made from the decomposition of 100.0 g of PbO2?
5. What is the percent composition (percent by mass of each element in a compound) of:
   1. Lead(II) chromate, PbCrO4, is used as a paint pigment (chrome yellow). What is the percentage composition of lead(II) chromate?                                                   (64.11% ??; 16.09% ??; 19.80% ?)

1. 2. H3PO4, Phosphoric acid, is used in detergents, fertilizers, toothpastes and flavoring in carbonated beverages. Calculate the percent composition by mass to two decimal places of H, P and O in this compound.                                                                                                 (3.09% ?; 31.60% ?; 65.31% ?)

1. 3. What is the percent composition by mass of aspartame (C14H18N2O5), the artificial sweetener NutraSweet?                                                                                             (57.12% ?; 6.18%?; 9.52% ?; 27.18% ?)

6. What is the empirical formula of each of the following compounds?

1. Talc by mass composition contains 19.2% Mg, 29.6% Si, 42.2% O and 9.0% H. (Mg3Si4O10H34)

2. Saccharin has by mass composition 45.89% C, 2.75% H, 7.65% N, 26.20% O and 17.50% S(C7H5NO3S)

3. Salicylic Acid, used in aspirin, contains 60.87% C, 4.38% H, and 34.75% O by mass composition. (C7H6O3)

4. L-Dopa, a drug used for the treatment of Parkinson’s disease, is 54.82% C, 5.62% H, 7.10% N, and 32.46% O by mass composition. (C9H11NO4)

7. What are the empirical and molecular formulas of the following compounds?
   1. Ibuprofen by mass composition is 75.69% C, 8.80% H and 15.51% O and the molecular mass is approximately 206 g/mol. (C13H18O2)

1. 2. Caffeine contains by mass composition 49.5% C, 5.15% H, 28.9% N and 16.5 % O and the molecular mass is about 195 g/mol. (C8H10N4O2)

Limiting reactant, Theoretical yield, and percent yield

8. What is the limiting reactant, and theoretical yield of NaCl in a reaction that produces sodium chloride from

8.00 g of sodium and 8.00 g of diatomic chlorine?

2Na (s) + Cl2 (g) → 2NaCl (s)                                                 

9. When 0.50 g of Cr and 0.75 g of H3PO4 react according to the following chemical equation?

2Cr + 2H3PO4    → 2CrPO4              + 3 H2

Calculate the theoretical yield for hydrogen gas?                      How Many Grams of N2 (g) Can Be Made from 9.05 g of NH3 Reacting with 45.2 g of CuO? NH3 (g) + 3 CuO (s) → N2 (g) + 3 Cu(s) + 3 H2O (l)

(a) Calculate the theoretical yield for N2?                             (5.30 g N2)

(a) If 4.61 g of N2 Are Made, What Is the Percent Yield? (87.0%)

5.30 g N₂

10. Silicon nitride is a very hard, high-temperature-resistant ceramic used as a component of turbine blades in jet engines. It is prepared according to the following equation:

3Si (s) + 2N2 (g)         →      Si3N4 (s)

1. Which is the limiting reactant when 2.00 g of Si and 1.50 g of N2 react? (Si is L.R; 3.33 g Si3N4 is T.Y)

2. If the actual yield is 2.55 g Si3N4, calculate the percent yield?                      (76.6 %)

1 ??? ??3?4    ) = 3.76 ? ??₃?₄