Q: A student measures the temperature of a solution to be $$79\ ^\circ\mathrm{C}$$, but the true value is $$85\ ^\circ\mathrm{C}. $$What is the percent error in this measurement?

$$\displaystyle \frac{79-85}{85} \times 100\% = -7.1\%$$

Question 1

A student measures the mass of a standard 100.00 g weight on two different balances. Balance A gives readings of 100.01, 99.99, 100.00, and 100.00 g. Balance B gives readings of 98.89, 101.09, 100.00, and 99.99 g. Which statement best describes the accuracy and precision of each balance?

Accepted Answer

Balance A is more precise and more accurate than Balance B.

Question 2

Which of the following best describes a measurement that is precise but not accurate?

Accepted Answer

Repeated measurements are close to each other but far from the true value.

Question 3

A student measures the temperature of a solution to be $$79\ ^\circ\mathrm{C}$$, but the true value is $$85\ ^\circ\mathrm{C}. $$What is the percent error in this measurement?

Accepted Answer

$$\displaystyle \frac{79-85}{85} 	imes 100\% = -7.1\%$$

Question 4

How many significant figures are in the number $$0.0101$$?

Accepted Answer

3

Question 5

Which of the following numbers has exactly four significant figures?

Accepted Answer

$$1.000 	imes 10^3$

Question 6

A rock has a mass of $$30\ \mathrm{g}$$ and a volume of $$6.7\ \mathrm{mL}. $$What is its density?

Accepted Answer

$$4.5\ \mathrm{g/mL}$$

Question 7

Which of the following best describes an isotope?

Accepted Answer

Atoms of the same element with different numbers of neutrons.

Question 8

Chlorine has two main isotopes: $$^{35}\mathrm{Cl} ($$mass $$=34.97\ \mathrm{u}$$, abundance $$=75.8\%) $$and $$^{37}\mathrm{Cl} ($$mass $$=36.97\ \mathrm{u}$$, abundance $$=24.2\%). $$What is the average atomic mass of chlorine?

Accepted Answer

$$35.47\ \mathrm{u}$$

Question 9

A neutral atom of copper-65 ($$^{65}\mathrm{Cu}) $$has how many protons, neutrons, and electrons?

Accepted Answer

29 protons, 36 neutrons, 29 electrons

Question 10

How many molecules are present in $$4$$ moles of $$\mathrm{CO}_2$$?

Accepted Answer

$$2.41 	imes 10$$^{24}$$

Question 11

What is the molar mass of $$\mathrm{H}_2\mathrm{SO}_4$$?

Accepted Answer

$$98.08\ \mathrm{g/mol}$$

Question 12

Convert $$67\ \mathrm{mL} to $$liters.

Accepted Answer

$$0.067\ \mathrm{L}$$

Question 13

Which of the following is a homogeneous mixture?

Accepted Answer

Saltwater

Question 14

Which of the following is the correct name for $$\mathrm{FeCl}_3$$?

Accepted Answer

Iron(III) chloride

Question 15

Which of the following is the correct formula for dinitrogen pentoxide?

Accepted Answer

$$\mathrm{N}_2\mathrm{O}_5$$

Question 16

A $$12\ \mathrm{kg}$$ object has a weight force of $$588\ \mathrm{N} on $$planet X. What is the gravitational acceleration on planet X?

Accepted Answer

$$49\ \mathrm{m/s}^2$$

Question 17

Which of the following ions has 10 electrons, 12 neutrons, and 12 protons?

Accepted Answer

$$\mathrm{Mg}^{2+}$$

Question 18

Which of the following best describes the difference between a compound and a mixture?

Accepted Answer

A compound has a fixed composition and can only be separated by chemical means, while a mixture has a variable composition and can be separated by physical means.

Question 19

What is the correct name for $$\mathrm{HNO}_3$$?

Accepted Answer

Nitric acid

Question 20

If you have $$3.0 	imes 10$$^{24}$$ atoms of hydrogen, how many moles of hydrogen do you have?

Accepted Answer

$$5.0$$ moles

Measurement in Chemistry: Accuracy, Precision, and Significant Figures

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