(D) The subtraction of from 4.8 giving the correct number of significant

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1 HCCS CHEM 1405 PRACTICE EXAM I: 5 th & 6 th & 7 th editions of Corwin s Introductory Chemistry: Concepts and Critical Thinking. Multiple Choices: Choose the best (one) answer. Show in bold. Questions break-down: Please see information in the Hints. 1. Which of the following values are correct concerning the maximum and minimum values of the measurement, ± 0.05 ml? (A) and (B) and (C) 15.1 and 15.0 (D) 15.6 and 15.0 (E) None of the above Hint: For 7 th ed., see Prerequisite Science Skill (PPS) p.p For both 5 th and 6 th ed., see Section Which of the following statement is wrong concerning the significant digits (Or say, significant figures)? (A) There are five significant digits in (B) There are three significant digits in (C) There are four significant digits in x (D) There are three significant digits in (E) There are four significant digits in Hint: For 7 th ed., see Prerequisite Science Skill (PPS) p. 15 and p.p For both 5 th and 6 th ed., see Section 2.2 & section 2.7 for significant figures in scientific notation. 3. Which of the following statement is correct concerning the significant figures? (A) The sum of and written in scientific notation and giving the correct number of significant digits is x (B) The subtraction of from 4.8 giving the correct number of significant digits is 0.8. (C) The sum of and giving the correct number of significant digits is (D) The subtraction of from 4.8 giving the correct number of significant digits is (E) None of the above. Hint: For 7 th ed., see Prerequisite Science Skill (PPS) p.p For both 5 th ed. and 6 th ed., see Section 2.4 for addition and subtraction and section 2.5 for multiplication and division. You need to memorize all the rules concerning the significant figures and the rules related to addition or subtraction and multiplication or division. Many 1

2 students do not know the differences between addition/subtraction and multiplication/division. See two examples below: Remember that the answers obtained from calculators are always WRONG when considering the significant figures. Ex = from calculator, which must be corrected with the least decimal points of the components, and thus it is , and thus it must be written in scientific notation and giving the correct number of significant figures as x Which of the following expression is not equivalent to x 10 4? (A) x 10 0 (B) x 10 1 (C) x 10 2 (D) x 10 3 (E) x 10 3 Hint: For 7 th ed., see Prerequisite Science Skill (PPS) p.p For both 5 th ed. and 6 th ed., see Section 2.6 for exponential numbers and section 2.7 for scientific notation. 5. Which of the following statement is true? (A) The result of multiplying x 10 2 and x 10 4 written in scientific notation and giving the correct number of significant figures is x (B) The result of multiplying 25.2 x 10 2 and x 10 4 written in scientific notation and giving the correct number of significant figures is x (C) The result of multiplying 25.2 x 10 2 and x 10 4 written in scientific notation and giving the correct number of significant figures is 2.94 x (D) The result of multiplying x 10 2 and x 10 4 written in scientific notation and giving the correct number of significant figures is x (E) The result of multiplying x 10 2 and x 10 4 written in scientific notation and giving the correct number of significant figures is 29.4 x Hint: For 7 th ed., see Prerequisite Science Skill (PPS) p.p For both 5 th ed. and 6 th ed., see: Section 2.5. When counting number of significant figures or significant digits, we always count from left to right. In a scientific notation, we only count the numbers before the multiplication sign (x). Choice (A): (25.20 x 10 2 ) x (1.167 x 10 4 ) = x 10 5 from calculator, which is usually wrong, when consider the significant digits. In multiplication, the number of significant digits is the same as the component which has the least significant digits. Since there are 4 significant figures in and so are for and thus the answer of the calculation result should have 4 significant figures. So the answer for (A) is x The reason that Choice (A) is wrong is due to the rounding error. This is because the result of multiplication 2

3 must match the least significant digits of the components. Do not confuse with the addition/subtraction rule. In addition or subtraction, the result must have the same decimal digits with the component which has the least decimal digits. After determining the decimal digits, then count the significant digits. Scientific notation can only have one digit in front of a decimal point. When the decimal point moves to the left side, the exponent becomes more positive, when it moves to the right, the exponent becomes more negative. Choice (B): The result or answer should contain 3 significant digits only. This is because 25.2 contain 3 significant digits and contains 4 significant digits. This is why Choice (C) is correct. 6. A solution contains 255 ml of ethanol and 375 ml of water. What is the percent of water in the solution? (A) 3.75 % (B) % (C) 2.55 % (D) 59.52% (E) None of the above. Hint: For 7 th ed., see Section 2.8, p ; For both 5 th ed. and 6 th ed., see Section Which of the following does not belong to the basic units in the metric system? (A) Meter (B) Kilogram (C) Pound (D) Centigrade (E) All of the above Hint: For 7 th edition, see Section 2.4; For both 5 th ed. and 6 th ed. see Section Which of the following conversion is correct? (A) 1 cm = 1 inch (B) 1 pound = kg = 454 g (C) 1 km = 100 m (D) 1 mg = 100 ug (E) 1 c.c. = 1 m 3 Hint: For 7 th edition, see Sections 2.2 to 2.4; p.p ; See both 5 th ed. and 6 th ed. Sections 3.2, 3.3, and Which of the following is wrong? (A) 1 L = 1000 ml (B) 1 ml = 1 c.c. = 1 cm 3 (C) 1 gal = L 3

4 (D) 1 mi = 1.61 km (E) None of the above is wrong. Hint: For 7 th edition, see Sections 2.2 to 2.4; p.p ; For both 5 th ed. and 6 th ed., see Sections 3.3, 3.4 and 3.5. For (C), 1 gal x (4 qt/1 gal) x (946 ml/1 qt) x (1 L/1000mL) = L For (D), 1 mi x ( 5280 ft/1 mi) x (12 in/1 ft) x (2.54 cm/1 in) x (1m /100 cm) x (1 km/1000 m) = 1.61 km. The ones shown above in choices are direct conversion information. 10. The initial water level in a 10-mL graduated cylinder reads 5.0 ml. After a marble is dropped into the cylinder, the water level reads 7.5 ml. What is the volume of the marble? (A) 5.0 ml (B) 7.5 ml (C) 2.5 ml (D) 12.5 ml (E) 15.0 ml Hint: For 7 th ed., see Section 2.7 p.p ; For both 5 th ed. and 6 th ed., see Section Which of the following will sink when dropped into water (d = 1.00 g/ml)? (A) bamboo ( d = 0.40 g/ml) (B) paraffin wax (d = 0.90 g/cm 3 ) (C) limestone (d = 2.8 g/cm 3 ) (D) helium gas ( d = g/ml) (E) ammonia (d = g/ml) Hint: For 7 th ed., see Section 2.8 or figure 2.5; For both 5 th ed. and 6 th ed., see Section 3.7 (or Fig. 3.5). 12. What is the volume for a substance with density of 2.5 g/cm 3 and mass of 0.5 kg? (A) 0.2 cm 3 (B) 2.0 cm 3 (C) 20.0 cm 3 (D) cm 3 (E) 5.0 cm 3 Hint: For 7 th ed., see Section 2.8; For both 5 th ed. and 6 th ed. see Section 3.7. Memorize the formula: density (g/cm 3 ) = mass (g) / volume (cm 3 ). Note: 1 kg = 1000 g. 13. Which of the following is equivalent to 230 o C? (A) 503 K, 446 o F (B) + 43 K, 300 o F (C) - 43 K, 230 o F (D) 300 K, o F 4

5 (E) 20 K, o F Hint: For 7 th ed., see Section 2.7; For both 5 th ed. and 6 th ed., see Section 3.8. Similar to example exercise 3.16 in 6 th edition. Memorize the formula: K = o C and then see which choice is closer to the answer calculated. o F = 1.8 x o C Note that there is no direct conversion between the K and o F. So in this question, you must convert K to o C first and then convert o C to o F. 14. How much energy is removed when a 350 g can of soda is placed in a refrigerator and cooled from 30 o C to 15 o C. Assume the specific heat of soda is identical with that of water, J/g- o C. (A) kj (B) kj (C) kj (D) 44 kj (E) 365 kj Hint: For 7 th ed., see Section 2.10; For both 5 th ed. and 6 th ed., see Section 3.9. Similar to example exercise 3.19 in 6 th edition. Memorize the formula: energy (q) = specific heat (s) x mass (g) x temperature change. Note that temperature change = final temperature initial temperature; also 1 kj = 1000 J and 1 calorie = 1 c = J. So q = x 350 x (15-30) = J = kj. Here - means that energy is removed. If it s +, it means that energy is absorbed. 15. Which of the following statement is concerning sublimation? (A) The phenomenon describes a solid melts into a liquid. (B) The phenomenon describes a liquid vaporizes into a vapor. (C) The phenomenon describes a direct change from a solid into a vapor. (D) The phenomenon describes a direct change from a gas to a solid. (E) None of the above. Hint: For 7 th ed., see p. 65; For both 5 th ed. and 6 th ed., see Section 4.1.; p. 61: 6 th ed.) 16. Which of the following material is a homogeneous mixture? (A) Alloy (B) Baking soda (C) Sodium atom (D) Table salt (E) Hydrogen gas Hint: For 7 th ed., see Section 3.2, p ; For both 5 th ed. and 6 th ed., see Section 4.2. When presented by chemical formulas mixture (like sugar water as H 2 O + C 6 H 12 O 6 ) usually contains at least one plus sign and the pure substance does not (like baking soda as Na 2 CO 3 ). 17. Which of the following chemical symbols is correctly matched? (A) Tin, Ti 5

6 (B) Sodium, So (C) Mercury, Hg (D) Potassium, P (E) Lead, Le Hint: For 7 th ed., see Section 3.3; For both 5 th ed. and 6 th ed., see Section 4.3. Check with periodic table and memorize them. 18. Which of the following statements is true? (A) Au, nonmetal (B) Hg, the only liquid metal (C) Al, nonmetal (D) Br, the only solid nonmetal (E) H, metal Hint: For 7 th ed., see Section 3.4, p. 74; for both 5 th ed. and 6 th ed., see Section 4.4. Check with periodic table. 19. Which of the following statements is true? (A) Most of the metals are located at the far right side of the periodic table. (B) Most of the nonmetals are located at the far left side of the periodic table. (C) B, Si, Ge, As, Sb, Te, Po and At are semimetals or say metalloids. (D) H, Li, Na, K, Rb, Cs and Fr are alkali metals. (E) He, Ne, Ar, Kr, Xe and Rn are halogens. Hint: For 7 th ed., see Section 3.4; for both 5 th ed. and 6 th ed. see Section 4.4. Check with periodic table. This is the definition. 20. Which of the following is/are physical properties? (A) Density and color (B) Conductivity & melting (i.e. freezing) point (C) Condensation & vaporization (D) Odor & magnetism (E) All of the above. Hint: For 7 th ed., see section 3.6; for both 5 th ed. and 6 th ed. Section 4.6. Definition: Physical properties include appearance, melting point, boiling point, sublimation (note: that is change from solid phase directly to vapor phase without going through the liquid phase), density, solubility in water (note: not reaction with water), changing color by mixing different paints (note: not changing color through a chemical reaction like acid-base reaction, oxidizationreduction reaction, or through the sunlight which contains UV lights). Physical changes are done through using the physical properties and they are the ones you can get them back by changing the temperature or pressure. The procedure used by adapting physical properties is called the physical process which does ont change the composition of the substance. Chemical properties are the ones you cannot get them back because the compositions are changed. Burning, rusting, baking, fermentation, fruit ripen, 6

7 milk turns sour (to lactic acid), wine turn sour (to vinegar), metabolism, zinc metal reacts with vinegar to produce hydrogen gas, sidewalk chalk reacts with vinegar to produce carbon dioxide gas, etc. are all chemical reactions. 21. Which of the following is a physical change? (A) Paper burns in the air. (B) Wine turns sour into vinegar. (C) Glucose ferments into ethyl alcohol. (D) Aluminum foil dissolves in hydrochloric acid (E) Dry ice vaporizes into a gas. Hint: For 7 th ed., see section 3.7; for both 5 th ed. and 6 th ed., see Section 4.7. Which of the following is a chemical change? (A) The fading of a carpet upon repeated exposure to sunlight. (B) The evaporation of fingernail-polish remover (acetone) from the skin. (C) The shiny appearance of silver. (D) The ability of dry ice to vaporize without melting. (E) The low mass (for a given volume) of aluminum relative to other metals. Hint: For 7 th ed., see Section 3.7; for both 5 th ed. and 6 th ed., see Section 4.7. Chemical change is the change that you can not get it back to original as the composition of the substance is altered. Or say, chemical change is a process using chemical property. 22. Which of the following statements is wrong? (A) The chemical formula for sulfuric acid is H 2 SO 4 indicating two hydrogen atoms, 1 sulfuric atom, and 4 oxygen atoms. (B) There are total 10 atoms in a molecule of glycerin, C 2 H 4 (OH) 2. (C) The chemical formula for nitroglycerin is C 3 H 5 O 3 (NO 2 ) 3 indicating there are 3 carbon atoms, 5 hydrogen atoms, 3 oxygen atoms, and 3 NO 2 units. (D) There are 2 carbon atoms, 4 hydrogen atoms, and 1 oxygen atom in the chemical formula of glycerin, C 2 H 4 (OH) 2. Hint: For 7 th ed., see section 4.1: Chemistry Connection p. 101; For See both 5 th ed. and 6 th ed. Section 4.5. The difference between answers (C) and (D) are that answer (C) expressed 3 NO 2 units and thus there are 3 oxygen atoms; while answer (D) does not say anything about OH units, and thus we have to include all H atoms together. Thus, there are 6 hydrogen and 2 oxygen atoms. 23. If g of zinc metal reacts with g of yellow powered sulfur, what is the mass of the zinc sulfide produced? (Law of Conservation of Mass) (A) g (B) g (C) g (D) All of the above. 7

8 (E) None of the above. Hint: For 7 th ed., see Section 3.8; for both 5 th ed. and 6 th ed., see Section Which of the following statements is correct? (A) When a steel cylinder containing air is heated from 25 o C to 50 o C. The kinetic energy of the gas is increasing. (B) When a steel cylinder containing air is heated from 25 o C to 50 o C. The kinetic energy of the gas is decreasing. (C) When a steel cylinder containing air is heated from 25 o C to 50 o C. The motion of the air molecules is decreasing. (D) When a steel cylinder containing air is heated from 25 o C to 50 o C. The motion of the air molecules is not changed. (E) When a steel cylinder containing air is heated from 25 o C to 50 o C. The mass of the air molecules is decreasing. Hint: For 7 th ed., see section 3.10; for both 5 th ed. and 6 th ed., see Section: Which of the following statements is wrong? (A) When uranium vaporizes water into steam, the nuclear energy is converted to heat energy. (B) When steam drives a turbine, the heat energy is converted to mechanical energy. (C) When a turbine spins and drives an electrical generator, the mechanical energy is converted to electrical energy. (D) Solar calculator converts light energy into electrical energy. (E) Lead-acid battery converts light energy into electrical energy. Hint: for 7 th ed., see section 3.10; for both 5 th ed. and 6 th ed., see Section