Download Ch1 – Arithmetic of Chemistry Problem Set

Ch1 – Arithmetic of Chemistry Problem Set
1. Name then determine the molecular weights of each of the following compounds : (a) P2O3 ; (b)
BaSO4 ; (c) Mg (C2H3O2)2 ; (d) (NH4)2Cr2O7
2. Calculate the percentage by mass of oxygen in the following compounds : (a) SO3 ; (b) CH3COOH
; (c) Ca(NO3)2 ; (d) (NH4)2SO4
3. A sample of glucose C6H12O6, contains 4.0 x 102 atoms of carbon.
a. How many atoms of hydrogen does it contain?
b. How many molecules of glucose does it contain?
c. How many moles of glucose does it contain?
d. What is the mass of the sample in grams?
4. (a) What is the molar mass of copper (II) nitrate, Cu(NO3)2? (b) What is the mass, in grams of 0.120
mol Cu(NO3)2? (c) How many moles of Cu(NO3)2 are present in 3.15 g of this substance? (d) How
many N atoms are present in 1.25 mg of Cu(NO3)2?
5. Calculate the mass, in grams, of each of the following :
a. 0.00150 mol SO2
b. 2.98 x 1021 atoms of Ar
c. 1.05 x 1020 molecules of C8H10N4O2.
6. Give the empirical formula of each of the following compounds if a sample contains
a. 0.0130 mol C, 0.0390 mol H, and 0.0065 mol O
b. 11.66 g iron and 5.01 g oxygen
c. 40.0 % C, 6.7% H, and 53.3% O.
7. Determine the empirical formula and molecular formulas of each of the following substances
a. ethylene glycol : 38.7% C, 9.7% H, and 51.6% O ; MW = 62.1 amu
b. caffeine : 49.5% C, 5.15% H, 28.9% N, and 16.5% O ; MW = 195 amu.
8. The alcohol in “gasohol” burns according to the following equation :
C2H5OH (l) + 3O2 (g) Æ 2CO2 (g) + 3H2O (l)
a. How many moles of CO2 are produced when 3.00 mol of C2H5OH is burned in this way?
b. How many grams of CO2 are produced when 3.00 g of C2H5OH is burned this way?
9. Ascorbic acid (Vitamin C) contains 40.92 % C, 4.58 % H and 54.50% O by mass. What is the
empirical formula of ascorbic acid?
10. Mesitylene, a hydrocarbon that occurs in small amount in crude oil, has an empirical formula of
C3H4. The experimentally determined molecular weight of this substance is 121 amu. What is the
molecular formula of mesitylene?
11. 2H2 (g) + O2 (g) Æ 2H2O (l)
How many moles of H2O can be produced from 1.57 mol O2?
12. 2C4H10 (l) +
13O2 (g) Æ 8CO2(g) + 10H2O(l)
How much CO2 can be produced by burning 1.00 g of C4H10?
How much O2 will be consumed?
13. A solution is made by dissolving 13.5 g of glucose, C6H12O6, in 0.100 kg of water. What is the mass
percentage of solute in this solution?
14. A 2.5 g sample of groundwater was found to contain 5.4 µg of Zn2+. What is the concentration in
parts per million?
15. A solution of hydrochloric acid contains 36% HCl by mass.
a. calculate the mole fraction of HCl in the solution
b. calculate the molality of HCl in the solution
16. Given the density of a solution of 5.0 g of toluene and 225 g of benzene is 0.876 g/mL, calculate
a. the molarity of the solution
b. the mass percentage of solute
17. Calcium reacts with water to form calcium hydroxide and hydrogen gas (H2). (a) Write a balanced
equation for the reaction. (b) How many grams of calcium hydroxide are produced if 10.0 g of
hydrogen gas was evolved?
18. (a) Calculate the molarity of a solution that contains 0.0345 mol NH4Cl in 400 mL solution. (b)
How many moles of HNO3 are present in 35.0 mL of a 2.20 M solution of HNO3? (c) How many
milliliters of 1.50 M KOH solution are needed to supply 0.125 mol KOH?
19. Calculate the mass percentage of CaCl2 in a solution containing 16.5 g CaCl2 in 456 g water.
20. Calculate the mole fraction of methyl alcohol CH3OH in the following solutions
a. 8.5 g CH3OH in 224 g H2O
b. 65.2 g CH3OH in 144 g CCl4
21. Calculate the molarity of each of the following solutions
a. 10.5 g NaCl in 350.0 mL of solution
b. 40.0 mL of 1.50 M HNO3 diluted to 0.500 L
c. 40.7 g LiClO3·3H2O in 125 mL solution
22. Calculate the molality of each of the following solutions
a. 13.0 g benzene C6H6 dissolved in 25.0 moles CCl4
b. 5.85 g NaCl dissolved in 0.250 L of water