Workshop CHE 166
Problem Set #2
1. What did Rutherford's alpha particle scattering experiment established?
2. How many protons (p+), neutrons (n0), and electrons (e-) are present in an atom of the isotope sulfur-31?
3. How many protons, neutrons, and electrons are present in an atom of the element bromine with the isotopic symbol
.
4. On the average, an atom of uranium (U) is approximately how many times heavier than an atom of potassium?
5. Boron obtained from borax deposits in Death Valley consists of two isotopes. They are boron-10 and boron-11 with atomic masses of 10.013 amu and 11.009 amu, respectively. The atomic mass of boron is 10.81 amu. [See periodic table.] Which isotope of boron is more abundant, boron-10 or boron-11?
6. Rigel is the bluish star at Orion's left knee. What if an expedition to Rigel-3 (a fictional planet) brought back a sample of magnesium for mass analysis. What is the atomic mass of magnesium from Rigel-3, if it has two isotopes with the following masses and abundances:
Magnesium- 24: 23.985 amu; 18.05%
Magnesium- 26: 25.982 amu; 81.95%
7. What is the (average) mass in grams of one atom of iron?
8. What is the (average) mass of one copper atom?
9. What is the (average) mass of 7.80 x 1018 carbon atoms?
10. Determine the number of moles of aluminum in 96.7 g of Al.
11. If phosphorus is monatomic, calculate the number of moles in 12.0 g of phosphorus.
12. One nanogram doesn't seem like a very large number. How many atoms are there in 1.00 ng of magnesium?
13. 0.274 moles of a substance weighs 62.5 g. What is the molar mass of the substance in units of g/mol?
14. What is the molar mass of acetaminophen, C8H9NO2?
15. The molar mass of aspirin is 180.2 g/mol. How many molecules of aspirin are present in one 500-milligram tablet?
16. What is the mass of 0.0250 mol P2O5?
17. How many moles are there in 77.3 g of NH3?
18. How many moles is 1.0 x 1019 HCl molecules?
19. Calculate the mass of 3.00 moles of CF2Cl2?
20. How many atoms are in 5.54 g F2?
21. How many sodium atoms are in 6.0 g of Na3N?
22. How many sulfur atoms are present in 25.6 g of Al2(S2O3)3?
23. How many grams of magnesium are in 75.0 g of Mg(NO3)2?
24. How many moles of Cl atoms are in 65.2 g CHCl3?
25. How many carbon atoms are in 10 lbs of sugar, C12H22O11?
26. How many grams of sulfur are contained in 6.0 g of Fe2(SO4)3?
27. What is the percent sodium by mass in the compound NaHCO3?
28. Calculate the percentage of gallium by mass in gallium oxide, Ga2O3.
29. Determine the percentage of each element in potassium carbonate, K2CO3.
30. Determine the percentage of each element in ethanol, C2H6O.
31. What is the percent oxygen in an oxygenated gasoline that contains 8.5% by mass of the additive MTBE as its only source of oxygen? Given the formula of MTBE is C5H12O.
32. 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?
33. A 5.325 g sample of methyl benzoate, a compound used in the manufacture of perfumes, is found to contain 3.758 g of carbon, 0.316 g of hydrogen, and 1.251 g of oxygen. What is the empirical formula of this substance?
34. Cyclopropane, a substance used with oxygen as a general anesthetic, contains only two elements, carbon and hydrogen. When 1.00 g of this substance is completely combusted, 3.14 g of CO2 and 1.29 g of H2O are produced. What is the empirical formula of cyclopropane? If its molar mass is 39.1 g/mol, what is the molecular formula of cyclopropane?
35.
(a) Nicotine is a compound found in tobacco leaves. Elemental analysis of nicotine gives the following data: C, 74.00%, H, 8.65%, and N, 17.35%. What is the empirical formula of nicotine?
(b) The molar mass of nicotine is 162 g/mol. What is the molecular formula of nicotine?
36. Give the empirical foumula of each of the following compounds if a sample contains
a) 0.0230 mol C and 0.0615 mol H
b) 5.28 g Sn and 3.37g F
c) 87.5% N and 12.5% H by mass
d) 10.4% C, 27.8% S and 61.7% Cl by mass
e) 21.7g C, 9.6g O and 68.7g F
f) 2.91g Na, 0.127 mol S and the rest oxygen, O
37. Which of the following compounds are likely to be ionic? Which are likely to be molecular? AlCl3, LiF, BaCl2, B2H6, KF, C3H8, KCN, Zn(NO3)2.38. For the ionic compounds found in Question #33, show the ions that make up the compound.