SEOCT Practice

Chemistry and Electricity

Chemistry

• Carbon atoms can link themselves together into long chains and rings to form a vast number of highly complicated molecules. Which of the following statements BEST explains why carbon atoms behave this way?

• A. They easily form ionic bonds with each other.• B. They easily form covalent bonds with each other.• C. They easily combine with atoms of oxygen.• D. They easily become highly charged ions.

• Answer - B

Chemistry

• Aluminum oxide, Al2O3, is produced by combining Al3+ and O2- particles. What type of compound has been formed?

• A. covalent• B. ionic• C. metallic• D. molecular

• Answer - B

Chemistry

• Which of the following pairs are isotopes of the same element?

• A. atom J (27 protons, 32 neutrons) and atom L (27 protons, 33 neutrons)• B. atom Q (56 protons, 81 neutrons) and atom R (57 protons, 81 neutrons)• C. atom V (8 protons, 8 neutrons) and atom W (7 protons, 8 neutrons)• D. atom S (17 protons, 18 neutrons) and atom T (18 protons, 17 neutrons)

• Answer - A

Chemistry• Use the table below to answer the following question.• Flame Color for Different Salts• Salt Flame Color• Sodium chloride yellow• Potassium chloride violet• Copper chloride blue• Calcium chloride red• Amy performed a flame test by burning a small amount of an unknown

substance in the flame of a Bunsen burner. The flame turned blue. It is MOST likely that the unknown substance contained

• A. calcium• B. potassium• C. sodium• D. copper

• Answer - D

Chemistry

• Which of the following is a chemical property of iodine?

• A. violet as a gas• B. silver-black as a solid• C. reacts with starch to give a dark blue color• D. a solid at room temperature

• Answer - C

Chemistry

• An ionic bond typically forms between certain types of elements. Which pair of elements will form an ionic compound?

• A. Na and Cu• B. K and Cl• C. Ne and O• D. Li and Mg

• Answer - B

Chemistry

• The number of protons in a neutral atom is equal to the number of

• A. electrons• B. neutrons• C. ions• D. isotopes

• Answer - A

Chemistry

• The melting of wax is a physical change, yet the burning of wax is a chemical change. What is the essential difference between the physical change and chemical change of wax in a burning candle?

• A. The burning of wax forms new compounds, while the melting of wax does not.

• B. A higher temperature is needed to burn wax than to melt wax.

• C. Melted wax can be separated into other substances, while solid wax cannot.

• D. Melted wax is a different phase of matter than solid wax.

• Answer - A

Chemistry

• Which pair of elements is MOST similar?• A. Ca and F• B. Na and Cl• C. Ne and Ar• D. Li and H

• Answer - C

Chemistry

• Which of the following contains the MOST atoms?

• A. K2MnO7

• B. Al2(SO4)3

• C. C4H4F4Cl2• D. Hg2(NO3)2

• Answer - B

Chemistry

• Look at the following equation. 2Al(s) + 3CuCl2(aq) 2AlCl3(aq) +3Cu(s)

This is an example of what type of reaction?• A. decomposition• B. double displacement• C. single displacement• D. synthesis

• Answer - C

Chemistry

• What is the name of the compound represented by the formula NO2?

• A. nitrogen dioxide

• B. dinitrogen monoxide

• C. nitrogen oxide

• D. mononitrogen dioxide

• Answer - A

Chemistry

• What is the formula of the compound containing Ca2+ and F−?

• A. CaF

• B. Ca2F

• C. CaF2

• D. CaF3

• Answer - C

Chemistry

• This table above shows the reaction of sodium chloride (NaCl) with silver nitrate (AgNO3) and the masses of the compounds involved in the reaction. How many grams of AgCl, x, are produced by the reaction?

• A. 16.98

• B. 28.67 Reaction NaCl+AgNO3 → AgCl+NaNO3

• C. 45.67• D. 62.67

• Answer - B

Mass

Before

(g)

11.69 33.98 0 0

Mass

After

(g)

0 0 X 17.00

Electricity

• A toaster is plugged into a wall outlet that has a voltage of 110 volts. If the toaster’s resistance is 10 ohms, what current runs through the toaster?

• A. 10 amperes• B. 11 amperes• C. 100 amperes• D. 1100 amperes

• Answer - B

Electricity

• A student connects three identical light bulbs in parallel to a dry cell as shown below. What happens when the student removes one of the light bulbs from its socket?

• A. All the light bulbs go out.• B. The other light bulbs remain on and will be equally

bright.• C. The other light bulbs remain on, one less bright and

the other the same brightness as before.• D. The other light bulbs remain on, one brighter and the

other less bright than before.

• Answer - B

Electricity• Bonnie sets up a thermocouple, as shown in the diagram

below. The iron and copper wires are wrapped together in two places that are at different temperatures, and a current flows in the circuit. As the temperature difference between the ends of the wires increases, the current in the circuit

• A. also increases• B. remains the same• C. decreases, but not to zero• D. totally stops flowing

• Answer - A

Electricity

• Four identical light bulbs are connected in a circuit as shown below. The current is greatest through which of the light bulbs?

• A. a• B. b• C. c• D. d

• Answer - D

Radioactivity

• Radioactive isotopes are commonly used as

• A. cooling agents• B. agricultural pesticides• C. nutritional supplements• D. tracers in biochemical reactions

• Answer - D

Radioactivity

• A radioactive substance has a half-life of 10 years. What fraction of a sample of the substance would be left after 30 years?

• A. 1/2

• B. 1/3

• C. 1/8

• D. 1/9

• Answer - C

Radioactivity

• Gold-191 is a radioactive isotope that has a half-life of 12.4 hours. If a lab starts with a 13.2-milligram sample of gold-191, how much will remain after 37.2 hours?

• A. 6.60 mg• B. 4.40 mg• C. 1.65 mg• D. 0.825 mg

• Answer - C

T (hr) Amount of Gold-191Remaining (mg)

0 13.212.4 6.6024.8 3.3037.2 1.65

Radioactivity

• Which of the following equations represents a nuclear fission reaction?

• A. • B. • C. • D.

• Answer – A The equation in choice A shows one large nucleus disintegrating into two smaller atomic nuclei, so choice A is correct. Choices B and D are incorrect because the reactions involve radioactive decay, not fusion. Choice C is incorrect because the equation represents a nuclear fusion reaction, not fission. Four smaller nuclei fuse together to produce one larger atomic nucleus.

Phase Change

• The diagram shows the motion of some aluminum atoms before and after a phase change. What phase change has occurred?

• A. condensation• B. freezing• C. vaporization• D. melting

• Answer - B

Phase Change

• Some ice crystals are released from the space shuttle into the near vacuum of space. Solar radiation causes a phase change. Which path indicated in the diagram BEST illustrates what happens to the ice crystals?

• A. AB• B. CD• C. EF• D. GH

• Answer – A (see next slide for explanation)

Phase Change

• In space, the pressure is essentially zero and constant. The path in the phase diagram must be at such a low pressure that an increase in temperature from incoming solar radiation will cause a phase change from solid to vapor. This means choice A is correct. Choice B is incorrect because the pressure is too high. This path would occur at normal atmospheric pressure. Choices C and D are incorrect. The temperature does not remain constant while the pressure changes in the near vacuum of space.

Acids and Bases

• The strip chart shows the pH of some common substances. Which substance is basic?

• A. lemon juice• B. rainwater• C. pure water• D. washing soda

• Answer - D

Acids and Bases

• Which of the following substances, when dissolved in water, will turn red litmus paper blue?

• A. KOH• B. NaCl

• C. H2O

• D. H2SO4

• Answer – A Choice A is the correct answer. Potassium hydroxide (KOH) contains the hydroxide ion (OH−). This ion will accept a proton (H+), so it is basic and will turn red litmus paper blue. Choice B is incorrect because NaCl is a neutral salt. Water is neutral as well, so choice C is incorrect. Choice D is incorrect because H2SO4 is a strong acid. It will turn blue litmus paper red.

Acids and Bases

• Borax detergent is dissolved in water. The solution turns red litmus paper blue and feels slippery to the touch. Which pH is possible for the solution?

• A. 1.5• B. 5.0• C. 7.0• D. 9.5

• Answer – D

Electricity

• A device that increases or decrease voltage in a power line is a

• A. commutator• B. generator• C. motor• D. transformer

• Answer – D

Magnetism

• The location of the strongest magnetic forces is

• A. magnetic poles• B. magnetic fields• C. electromagnets• D. magnetic domain

• Answer – A

Magnetism

• The north pole of one magnet will be attracted to

• A. another north pole• B. a south pole• C. the middle of a magnet• D. none of the above

• Answer – B

Magnetism

• The strength of a magnetic field created by a current in a wire can be increased by

• A. using shorter wire• B. decreasing the current in the wire• C. using longer wire• D. wrapping the wire into a coil

• Answer – D