CHEMISTRY Practice exam #1 answer key September 13, 2010

Transcription

1 CHEMISTRY Practice exam #1 answer key September 13, Which metric prefix means 1 x 10-9? a. kilo b. nano c. pico d. micro e. milli kilogram(s) contains this many grams. a b c. 55 d e A scientist obtains the number on a calculator. If this number actually has four (4) significant figures, how should it be written? a b c d e The density of liquid chloroform is 1.48 g/ml. What is its density in units of lb/in 3? (2.54 cm = 1 in., lb = 1 kg) a lb/in 3 b lb/in 3 c lb/in 3 d lb/in 3 e lb/in Kelvin equals a. 151 F b. 273 F c. 697 F d. 151 C e. 697 C 6. The freezing point and boiling point of water are often used to calibrate thermometers. Give those temperatures in degrees Celsius. a. 32 and 212 b. 0 and 100 c. 273 and 373 d. 100 and 273 e. 0 and As warm water sits in a cool room, you measure the temperature change ( T = T final T initial ). Which of the following is true? a. The temperature change ( T) is bigger if you are measuring in F. b. The temperature change ( T) is bigger if you are measuring in C. c. The temperature change ( T) will be the same regardless of the scale you use. d. Answer A or B is correct, depending on the difference in temperature between the water and the room. e. None of the above.

2 8. In 1984, some drums of uranium hexafluoride were lost in the English Channel, which is known for its cold water (about 15 C). The melting point of uranium hexafluoride is 148 F. In what physical state is the uranium hexafluoride in these drums? a. solid b. liquid c. gas d. a mixture of solid and liquid e. not enough information 9. The boiling of water is a a. physical change because the water merely disappears b. physical change because the gaseous water is chemically the same as the liquid c. chemical change because heat is needed for the process to occur d. chemical change because a gas (steam) is given off e. chemical and physical damage 10. Which of the following is not a physical property of water? a. Water boils at 100 o C. b. Water freezes at 32 o F. c. Water can be broken down into hydrogen gas and oxygen gas. d. Water is a liquid at room temperature. e. Water dissolves sugar. 11. Which of the following describes a chemical change? a. Ethanol boils when heated. b. Ethanol is a clear, colorless liquid. c. Ethanol mixes with water. d. Ethanol can be produced by the fermentation of grapes. e. Ethanol evaporates quickly at room temperature. 12. are substances with constant composition that can be broken down into elements by chemical processes. a. Solutions b. Mixtures c. Compounds d. Quarks e. Heterogeneous mixtures 13. In a chemical reaction, 36 g of water is broken down to yield 32 g of oxygen gas and 4 g of hydrogen gas. This is an example of: a. The Law of Conservation of Energy b. The Law of Conservation of Mass c. Dalton's Atomic Theory d. The Law of Constant Composition e. The Law of Multiple Proportions 14. Which of the following pairs of compounds can be used to illustrate the law of multiple proportions? a. NH 4 and NH 4 Cl b. ZnO 2 and ZnCl 2 c. H 2 O and HCl d. NO and NO 2 e. CH 4 and CO Consider the following two compounds: H 2 O and H 2 O 2. According to the law of multiple proportions, the ratio of hydrogen atoms per gram of oxygen in H 2 O to hydrogen atoms per gram of oxygen in H 2 O 2 is a. 1:1 d. 2:2 b. 2:1 e. 4:1 c. 1:2

3 16. How many of the following postulates of Dalton's atomic theory are still scientifically accepted? I. All atoms of the same element are identical. II. Compounds are combinations of different atoms. III. A chemical reaction changes the way atoms are grouped together. IV. Atoms are indestructible. a) 0 b) 1 c) 2 d) 3 e) Which of the following is not the symbol of an element? a. CO b. Ag c. Cu d. C e. Ni 18. Which of the following is a metal? a. Hydrogen (H, atomic number 1) b. Carbon (C, atomic number 6) c. Boron (B, atomic number 5) d. Iridium (Ir, atomic number 77) e. Radon (Rn, atomic number 86) 19. All of the following are characteristics of metals except: a. good conductors of heat b. malleable c. ductile d. often lustrous e. tend to gain electrons in chemical reactions 20. Which of the following are incorrectly paired? a. Sr, alkaline earth metal b. Ta, transition metal c. F, halogen d. As, halogen e. V, transition metal 21. Which one of the following statements about atomic structure is false? a. An atom is mostly empty space. b. Almost all of the mass of the atom is concentrated in the nucleus. c. The protons and neutrons in the nucleus are very tightly packed. d. The number of protons and neutrons is always the same in the neutral atom. e. All of the above statements (a-d) are true. 22. Which statement about electrons is false? a. All atoms have electrons as part of their structure. b. Electrons have much less mass than any atom. c. Electrons are found in the nucleus of the atom. d. Electrons are negatively charged. e. Electrons are attracted to positively charged electrodes. 23. Rutherford's gold foil experiment used alpha particles to reveal that: a. Isotopes exist b. Atoms have electrons c. Atoms have neutrons d. Atoms are radioactive e. Atoms have a nucleus

4 24. If the Thomson model of the atom had been correct, Rutherford would have observed: a. Alpha particles going through the foil with little or no deflection. b. Alpha particles greatly deflected by the metal foil. c. Alpha particles bouncing off the foil. d. Positive particles formed in the foil. e. None of the above observations is consistent with the Thomson model of the atom. 25. By knowing the number of protons a neutral atom has, you should be able to determine a. the number of neutrons in the neutral atom b. the number of electrons in the neutral atom c. the name of the atom d. two of the above e. none of the above 26. Which of the following is incorrect? a. 63 Cu has 29 protons, 29 electrons and 34 neutrons b. 55 Mn has 25 protons, 25 electrons and 30 neutrons c. 37 Cl has 20 protons, 20 electrons and 20 neutrons d. 74 Se has 34 protons, 34 electrons and 40 neutrons e. 40 Ar has 18 protons, 18 electrons and 22 neutrons 27. Which of the following atomic symbols is incorrect? a C b Cl c P d K e N 28. An element containing 32 protons, 32 electrons and 41 neutrons will have the symbol: a. 73 Ta b. 41 Ge c. 41 Nb d. 73 Nb e. 73 Ge 29. Which of the following statements about two isotopes is false? a. They will have the same atomic numbers. b. They will have the same atomic weights. c. They will have the same charge on the nucleus. d. They will have different numbers of neutrons. e. They will have essentially the same chemical reactivity. 30. Which element can be classified as a noble gas? a. O b. Na c. Kr 31. Which element can be classified as an alkaline earth metal? a. Ag b. Au c. Na 32. The chemical compound C 6 H 4 (COOH) 2 can also be represented as: a. C 7 H 6 O 2 b. C 7 H 5 O 2 c. C 7 H 5 O 4 d. Ti e. P d. Al e. Mg d. C 8 H 6 O 2 e. C 8 H 6 O 4

5 33. You are given a compound with the formula MCl 2, in which M is a metal. You are told that the metal ion has 25 electrons. What is the identity of the metal? a. Mn b. Al c. Cu d. Fe e. Co 34. Which formula-name combination is incorrect? a. SeCl 4 selenium chloride b. N 2 O 3 dinitrogen trioxide c. P 4 O 10 tetraphosphorus decaoxide d. AsF 5 arsenic pentafluoride e. SF 6 sulfur hexafluoride 35. Find the correct combination of protons and electrons below for the magnesium ion. a. 12 protons and 10 electrons d. 24 protons and 24 electrons b. 12 protons and 12 electrons e. 24 protons and 22 electrons c. 12 protons and 14 electrons 36. Which of the following is not an ionic compound? a. MgCl 2 b. H 2 S c. NaF d. AlCl 3 e. CaO 37. Give the formula for the ionic compound that forms between magnesium and nitrogen. a. MgN d. MgN 2 b. Mg 2 N e. Mg 3 N 2 c. Mg 3 N 38. Which ion is incorrectly named? a. K + potassium ion b. Cr 4+ chromium(iv) ion c. Ba 2+ barium ion d. Al 3+ aluminum(iii) ion e. Ni 2+ nickel(ii) ion 39. Which compound is incorrectly named? a. MgO magnesium(ii) oxide b. Fe 2 O 3 iron(iii) oxide c. CsCl cesium chloride d. K 2 S potassium sulfide e. Na 3 N sodium nitride 40. The formula for lithium dihydrogen phosphate is a. LiH 2 PO 4 b. Li(HPO 4 ) 2 c. LiHPO 4 d. Li 2 HPO 4 e. Li 2 H 2 PO 4