Q: A student needs to convert 5.00 km to centimeters. What is the correct answer using dimensional analysis?

$$5.00 \times 10^5$\ \mathrm{cm}$$

Question 1

A sample of an unknown metal has a mass of 45.6 g and a volume of 16.0 mL. What is the density of the metal, and which SI unit should be used for the answer?

Accepted Answer

$$2.85\ \mathrm{g/mL}$$

Question 2

Which of the following statements about significant figures is correct?

Accepted Answer

Zeros between nonzero digits are always significant.

Question 3

A chemist needs to prepare 250.0 mL of a solution. What is this volume in liters, using the correct number of significant figures?

Accepted Answer

$$0.2500\ \mathrm{L}$$

Question 4

Which of the following is a derived SI unit?

Accepted Answer

$$\mathrm{m^3$} ($$cubic meter)

Question 5

A student measures the mass of a beaker as 125.0 g and then adds 15.25 g of salt. What is the total mass, reported with the correct number of significant figures?

Accepted Answer

$$140.3\ \mathrm{g}$$

Question 6

Which scientist is credited with discovering the electron, and what experiment led to this discovery?

Accepted Answer

J.J. Thomson; cathode ray tube experiment

Question 7

Which of the following elements is an alkaline earth metal?

Accepted Answer

Magnesium ($$\mathrm{Mg})$$

Question 8

A neutral atom of $$^{37}\mathrm{Cl}$$ contains how many protons, neutrons, and electrons?

Accepted Answer

17 protons, 20 neutrons, 17 electrons

Question 9

Which of the following compounds is named correctly?

Accepted Answer

Aluminum sulfate: $$\mathrm{Al_2$(SO_4$)_3}$$

Question 10

Calculate the average atomic mass of an element with two isotopes: 60.0% $$^{63}\mathrm{Cu} ($$mass = 62.93 u) and 40.0% $$^{65}\mathrm{Cu} ($$mass = 64.93 u).

Accepted Answer

$$63.73\ \mathrm{u}$$

Question 11

Which of the following best describes an ionic compound?

Accepted Answer

A compound composed of metal and nonmetal ions held together by electrostatic forces

Question 12

How many moles are in 25.0 g of glucose ($$\mathrm{C_6H_{12}O_6$}$$)? (Molar mass = $$180.16\ \mathrm{g/mol})$$

Accepted Answer

$$0.139\ \mathrm{mol}$$

Question 13

A compound contains 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen by mass. What is its empirical formula?

Accepted Answer

$$\mathrm{CH_2O}$$

Question 14

Which of the following is an example of a physical change?

Accepted Answer

Boiling water to produce steam

Question 15

A student needs to convert 5.00 km to centimeters. What is the correct answer using dimensional analysis?

Accepted Answer

$$5.00 	imes 10^5$\ \mathrm{cm}$$

Question 16

Which of the following best describes the difference between an exact number and a measured number?

Accepted Answer

Exact numbers have no uncertainty; measured numbers have uncertainty.

Question 17

A sample contains $$3.01 	imes 10$$^{23}$$ molecules of water. How many moles of water are present?

Accepted Answer

$$0.500\ \mathrm{mol}$$

Question 18

Which of the following is the correct name for $$\mathrm{N_2O_5}$$?

Accepted Answer

Dinitrogen pentoxide

Question 19

A patient receives an intravenous solution containing $$0.90\ \mathrm{g} of$$ $$\mathrm{NaCl}$$ per $$100.0\ \mathrm{mL} of $$solution. What is the percent by mass of $$\mathrm{NaCl} in $$the solution, assuming the density of the solution is $$1.00\ \mathrm{g/mL}$$?

Accepted Answer

$$0.90\%$$

Question 20

Which of the following best describes the classification of air?

Accepted Answer

A homogeneous mixture

CHEM 141 Exam 1 Study Guide: Matter, Atoms, and Molecules

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