Chapter One

Chapter OneChemists andChemistry

QuestionWhich of the following is an example of aquantitative observation?a) Solution A is a darker red color thansolution B.b) The grass is green.c) Substance A has a greater mass thansubstance B.d) The temperature of the water is 45°C.Copyright © Houghton Mifflin Company. All rights reserved. 1 | 2

Answerd) The temperature of the water is 45°C.A quantitative observation includes ameasurement (numerical) and a unit.Copyright © Houghton Mifflin Company. All rights reserved. 1 | 3

QuestionThe glassware shown below is called a buret. The buretis filled to the zero mark (at the top) with a solution andthe solution is transferred to a beaker. What volume oftransferred solution should be reported?a) 20 mLb) 22 mLc) 22.0 mLd) 22.00 mLe) 25 mLCopyright © Houghton Mifflin Company. All rights reserved. 1 | 4

Answerc) 22.0 mLIn a measurement, we always include oneuncertain digit. The graduations on thisburet are in 1-mL units, so we canestimate the volume to the tenths place.Copyright © Houghton Mifflin Company. All rights reserved. 1 | 5

QuestionThe boiling point of a liquid was measured in the lab, with thefollowing results:TrialBoiling Point1 22.0°C ± 0.12 22.1°C ± 0.13 21.9°C ± 0.1The actual boiling point of the liquid is 28.7°C. The results of thedetermination of the boiling point area) accurate and precise.b) precise but inaccurate.c) accurate but imprecise.d) inaccurate and imprecise.Copyright © Houghton Mifflin Company. All rights reserved. 1 | 6

Answerb) precise but inaccurate.The measurements are precise becausethey are all in close agreement with oneanother. However, they are relatively farfrom the true value, so they areinaccurate.Copyright © Houghton Mifflin Company. All rights reserved. 1 | 7

Question_______ reflects the reproducibility of agiven type of measurement.a) Accuracyb) Precisionc) Certaintyd) Systematic errore) Random errorCopyright © Houghton Mifflin Company. All rights reserved. 1 | 8

Answerb) PrecisionMeasurements are precise if they arerelatively close to one another, regardlessof how close they are to the true answer.Copyright © Houghton Mifflin Company. All rights reserved. 1 | 9

Question_______ is the agreement of a particularvalue with the true value.a) Accuracyb) Precisionc) Certaintyd) Systematic errore) Random errorCopyright © Houghton Mifflin Company. All rights reserved. 1 | 10

Answera) AccuracyIf a measurement is in close agreementwith the true value, it is an accuratemeasurement.Copyright © Houghton Mifflin Company. All rights reserved. 1 | 11

QuestionAfter performing a calculation in the lab, thedisplay on your calculator reads “0.023060070”.If the number in the answer is to have fivesignificant figures, what result should you report?a) 0.0230b) 0.00231c) 0.023060d) 0.2367e) 0.02306Copyright © Houghton Mifflin Company. All rights reserved. 1 | 12

Answerc) 0.023060The leading zeros are not significant, butthe captive zero and the trailing zero aresignificant.Copyright © Houghton Mifflin Company. All rights reserved. 1 | 13

QuestionHow many significant figures are in thenumber 0.03040?a) 1b) 2c) 3d) 4e) 5Copyright © Houghton Mifflin Company. All rights reserved. 1 | 14

Answerc) 4The leading zeros are not significant, butthe captive zero and the trailing zero aresignificant.Copyright © Houghton Mifflin Company. All rights reserved. 1 | 15

QuestionThe beakers below have different precisions.You pour the water from these three beakers into onecontainer. What is the volume in this container reportedto the correct number of significant figures?a) 78.817 mLb) 78.82 mLc) 78.8 mLd) 79 mLCopyright © Houghton Mifflin Company. All rights reserved. 1 | 16

Answerd) 79 mLIn a measurement, we always include one uncertain digit.In this case, the first measurement could be 26.4 mL ±0.1 mL, the second could be 26 mL ± 1 mL, and the thirdcould be 26.42 mL ± 0.01 mL. When adding, the resulthas the same number of decimal places as the leastprecise measurement—in this case, to the ones place.So the answer is 26.4 + 26 + 26.42 = 78.82 mL, whichmust be rounded to 79 mL.Copyright © Houghton Mifflin Company. All rights reserved. 1 | 17

QuestionExpress 3140 in scientific notation.a) 3.14 × 10 3b) 3.14 × 10 -3c) 3.140 × 10 3d) 3.140 × 10 -3Copyright © Houghton Mifflin Company. All rights reserved. 1 | 18

Answera) 3.14 × 10 310 3 = 1000, and 3.14 × 1000 = 3140. We losethe zero because it is not significant (it is aplaceholder). If the zero was significant, weshould write the number as “3140.”.Copyright © Houghton Mifflin Company. All rights reserved. 1 | 19

QuestionA solution is also aa) heterogeneous mixture.b) homogeneous mixture.c) compound.d) distilled mixture.e) pure mixture.Copyright © Houghton Mifflin Company. All rights reserved. 1 | 20

Answerb) homogeneous mixture.Solutions can be liquids in liquids (such asrubbing alcohol, which consists of isopropanolin water), solids in liquids (such as sugar water),a mixture of gases (such as air), or even amixture of solids (such as brass, which consistsof a mixture of copper and zinc).Copyright © Houghton Mifflin Company. All rights reserved. 1 | 21

QuestionWhich of the following statements is false?a) Solutions are always homogeneousmixtures.b) Atoms that make up a solid are mostlyopen space.c) Elements can exist as atoms ormolecules.d) Compounds can exist as elements ormolecules.Copyright © Houghton Mifflin Company. All rights reserved. 1 | 22

Answerd) Compounds can exist as atoms ormolecules.Elements can be atoms (such as He) ormolecules (such as O 2 ), but compoundsmust exist as molecules.Copyright © Houghton Mifflin Company. All rights reserved. 1 | 23