Practice Problems

Question: Which of the following numbers has three significant figures? A. 0.034 B. 0.0340 C. 0.030 D. 3.4 x 10-2 Answer: B - The first two digits merely locate the decimal point. The other choices have two significant figures.

Question: In treating experimental data, a student multiplies 1.627 x 0.0148 and then divides by 2.303. The answer should be reported as 10-2 x A. 1.0 B. 1.05 C. 1.046 D. 1.04557534 Answer: B - The smallest number of significant figures, three, is in 0.0148.

Question: When you add the numbers 73 and 125.6, the sum will have ____ significant figures. A. 2 B. 3 C. 4 D. 6 Answer: B - The sum, 198.6, is rounded off the nearest unit, consistent with the uncertainty implied in the number 73.

Question: A certain glucose solution has a density of 1.15 g/cm3. The volume occupied by 105 g of this solution, in cm3, is: A. 121 B. 105 C. 91.3 D. 0.0110 Answer: C - Volume = mass/density

Question: A steel screw has a mass of 14.5 g. In kilograms, the SI unit of mass, this is 1.45 x A. 10-3 B. 10-2 C. 102 D. 104 Answer: B - 14.5 g x 1 kg/103g

Question: Which of the following is equivalent to a volume of 0.100 l (dm3)? A. 0.100 cm3 B. 10.0 cm3 C. 1.00 x 102 cm3 D. 1.00 x 10-2 cm3 Answer: C - 0.100 l x 103 cm3/l

Question: The number of kilojoules that is equivalent to 435 J is A. 0.435 B. 435 C. 4350 D. something else Answer: A - 435 J x 1 kj/103J

Question: Mercury has a density of 13.6 g/cm3. Its density expressed in kg/l or kg/dm3 is: A. 1.36 x 107 B. 1.36 x 104 C. 13.6 D. 1.36 x 10-2 Answer: C - 13.6 g/cm3 x 103 cm3/l kg/103g

Question: A patient was given a 2.0 cm3 injection of a medication having a density of 1.25 g/cm3. The number of grams administered was A. 0.40 B. 0.625 C. 1.6 D. 2.5 Answer: D - Mass = density x volume. Note the cancellation of units.

Question: If radioactive dating reveals the age of a manuscript to be between 1150 and 1390 yr, its age may be represented as A. 1 x 103 yr B. 1.3 x 103 yr C. 1.27 x 103 yr D. 1.270 x 103 yr Answer: B - The implied uncertainty gives a range of 1140 to 1400, This is equivalent to the uncertainty indicated by choice B.

Question: The transition metals are located at the ____ of the Periodic Table. A. left side B. right side C. bottom right D. center Answer: D - Perhaps "left of center" would be better.

Question: The zigzag line separates the nonmetals from the metals. It also lies at the center of the A. Periodic Table B. transition series C. metalloids D. noble gases Answer: C - For example, both Ge and As are considered metalloids.

Example Problem Use the Periodic Table to fill in the two appropriate labels. Element Metal, metalloid   or nonmetal Main group or transition 11Na (sodium) _______ _______ 17Cl (chlorine) _______ _______ 26Fe (iron) _______ _______ 32Ge (germanium)   _______ _______ Answer: Na metal main group Cl nonmetal   main group Fe metal transition Ge metalloid main group

Example Problem A cubic inch of copper weighs 147 g. What is the density of the metal in kg/m3? (1 in = 2.54 cm) Answer: Density = mass/volume         = 147 g / in3 x 1 Kg / 103g x (1 in / 2.54 cm x 102cm / m)3         = 8.97 x 103 kg/m3

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