Practice Hour Examination I. Use the Periodic Table in your book. Normally one will be provided. These are some sample problems.

Transcription

1 Chemistry 1111 bruary 2011 Practice Hour Examination I Use the Periodic Table in your book. Normally one will be provided. These are some sample problems. 1. What is the average mass (in grams) of one atom of lithium? a x b x10-24 c. 3 d e x Cumene is a compound composed of only C and H. It contains 89.9% C. What is its empirical formula? a. CH b. C 2 H 3 c. C 3 H 4 d. C 5 H 9 e. C 7 H How many oxygen atoms are represented in the expression: Ca(NO 3 ) 2? a. 3 b. 6 c. 10 d Sulfur trioxide, SO 3, forms when sulfur dioxide, SO 2, reacts with oxygen. The reaction is written: 2 SO 2 + O 2 2 SO 3 A 16 gram sample of SO 2 reacts form 18 grams of SO 3. What is the percent yield? a. 60% b. 75% c. 80% d. 90% e % 5. Very careful measurements made with an analytical balance determined the mass of a small crystal to be grams. How many significant figures are expressed in this quantity? a. 1 b. 2 1

2 c. 3 d. 4 e The equation below shows the chemistry when sodium borohydride is treated with sulfuric acid. (This is a method for preparing diborane, B 2 H 6.) When the equation is balanced, what is the coefficient of hydrogen? _2 NaBH 4 + H 2 SO 4 B 2 H H 2 + Na 2 SO 4 a. 1 b. 2 c. 3 d. 4 e What is the mass in grams of mole of β-fructose, C 6 H ? a g b. 180 g c g d g 8. An object that has a mass of 2 kg on Earth would have a. the same mass on the Moon b. a higher mass on the Moon c. a lower mass on the Moon d. no mass on the Moon. e. none of the above 9. Which volume contains 1 milliliter? a. 1 mm x 1 mm x 1 mm b. 1 cm x 1 cm x 1 cm c mm x 0.01 mm x 0.01 mm d. 0.1 mm x 0.1 mm x 0.1 mm e. 10 cm x 10 cm x 10 cm 10. A sample of pure strontium arsenate is 38.68% strontium by mass. What is the percent strontium by mass in a sample of pure strontium arsenate with twice the mass of the first sample? a % b % c % d. none of the above 11. There are two known isotopes of Surprisium, the element of surprise. 330 Su has a natural abundance of 75%. If the atomic mass on the periodic table is then the mass of the second isotope is 2

3 a. 325 amu b. 327 amu c. 328 amu d. 329 amu e. 331 amu 12. You are setting up a reaction between two chemicals that react according to the equation 3 A + 4 B products. If you start with 1.00 mole each of both A and B, which chemical will be in excess at the end, and by how much (assuming the reaction goes to completion)? a. A is in excess by mol b. A is in excess by mol c. B is in excess by mol d. Neither A nor B is in excess, because the reaction "goes to completion." e. B is in excess by mol. 13. How many iron atoms are present in 43.6 g of Cl 3? a x b x c x d e A sample of glucose, C 6 H 12 O 6, contains 4.0 x atoms of carbon. How many atoms of hydrogen and how many molecules of glucose does it contain? a. 8.0 x atoms of H; 8.0 x molecules of glucose b. 8.0 x atoms of H; 4.0 x molecules of glucose c. 4.0 x atoms of H; 4.0 x molecules of glucose d. 8.0 x atoms of H; 6.7 x molecules of glucose e. 8.0 x atoms of H; 2.4 x molecules of glucose 15. If the reaction of zinc with hydrochloric acid produces volume V of hydrogen gas when mass M of zinc is used, then using twice as much zinc will result in: a. a volume 2 V of hydrogen being produced b. more than V, but less than 2V of hydrogen being produced c. a volume V of hydrogen being produced d. a volume less than V of hydrogen gas being produced e. one cannot tell from this information 16. Because of the high heat and low humidity in the summer in Death Valley, California, a visitor requires about one liter of water for every two miles traveled on foot. If the density of water is approximately 1.0 g/ml at 45 C, how many kilograms of water are required for a person to walk 30 kilometers in Death Valley. (One mile is km and one liter is quart.) a. 0.9 kg b. 70 kg 3

4 c. 9.3 kg d. 7.0 x 10 2 kg 17. Which of the following is part of Dalton's atomic theory? a. atoms break down during radioactive decay b. atoms are rearranged but not changed during a chemical reaction c. atoms contain protons, neutrons, and electrons d. isotopes of the same element have different masses 18. Which of the following would be an isotope of an atom with atomic number 34 and mass number 76? An atom with: a. an atomic number of 32 and a mass number of 76 b. an atomic number of 34 and a mass number of 80 c. 42 neutrons and 80 protons d. 42 protons and 80 neutrons 19. Which of the species below has 28 protons and 26 electrons? a b c. Ni Ans 54 d. 28 Ni e Automobile antifreeze often contains a compound called ethylene glycol. Analysis of pure ethylene glycol shows that it contains only carbon, hydrogen, and oxygen. As sample of ethylene glycol is burned in oxygen and the weights of CO 2 and H 2 O resulting are as follows: weight of sample burned = 15.5 mg weight of CO 2 formed = 22.0 mg weight of H 2 O formed = 13.5 mg The empirical formula of ethylene glycol is: a. C 2 H 4 O 4 b. C 2 H 6 O 2 c. CH 3 O d. C 2 H 8 O 3 e. None of the above 4

5 21. A 5.91 gram sample of a mysterious compound contains 2.03 x atoms. What is this compound s molar mass? 2.03 x10 22 atoms/6.01 x10 23 atoms/mol =.0338 mol mass/gmw = mol gmw = 5.91/ gmw = Write formulas for the following compounds: Iron (III) cyanide Aluminum sulfate Tin (II) bromide Calcium phosphate Potassium sulfide (CN) 3 Al 2 (SO 4 ) 3 SnBr 2 Ca 3 (PO 4 ) 2 K 2 S 23. Write the systematic names for the following compounds: PbO 2 Co(NO 2 ) 2 KMnO 4 H 2 SO 4 NCl 3 lead (IV)oxide Cobalt (II)nitrite potassium permanganate sulfuric acid nitrogen trichloride 24. The density of iron is about 7.86 g/cm 3. What would be mass in kilograms of 1 cubic meter of iron? 1 m = 100 cm 1 m 3 =(100 cm) 3 = 1 x10 6 cm cm 3 /m 3 x 7.86 g/cm 3 = 7.86x10 6 g/1000g/kg = 7.86 x10 3 kg 25. Balance the following chemical reactions: a. 4 NH O 2 2 N H 2 O b. C 28 H O 2 28 CO H 2 O c. Ca 3 (PO 4 ) 2 + 8C Ca 3 P 2 + 8CO d. Al 2 O 3 + 6F 2 2AlF 3 + 3OF 2 e. 2NaNO 3 + H 2 SO 4 Na 2 SO HNO 3 5