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 of the following is the correct calculation using significant figures?

Accepted Answer

$$\frac{45.6\ \mathrm{g}}{16.0\ \mathrm{mL}} = 2.85\ \mathrm{g/mL}$$

Question 2

Which of the following statements about isotopes is correct?

Accepted Answer

Isotopes of an element have the same number of protons but different numbers of neutrons.

Question 3

A compound is found to contain 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen by mass. What is the empirical formula of the compound?

Accepted Answer

$$\mathrm{CH_2O}$$

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 sample as 12.30 g and the volume as 4.0 mL. How many significant figures should the calculated density have?

Accepted Answer

2

Question 6

Which of the following best describes the difference between an ion and an isotope?

Accepted Answer

An ion has a different number of electrons, while an isotope has a different number of neutrons.

Question 7

Which scientist is credited with discovering the electron and how?

Accepted Answer

J.J. Thomson, using the cathode ray tube experiment.

Question 8

A patient receives 250.0 mg of a medication. How many grams is this?

Accepted Answer

$$0.250\ \mathrm{g}$$

Question 9

Which of the following is the correct name for $$\mathrm{$$FeCl_3$$}$$?

Accepted Answer

Iron(III) chloride

Question 10

A sample contains 0.500 mol of $$\mathrm{NaCl}. $$What is the mass of the sample? ($$\mathrm{Na} = 22.99\ \mathrm{g/mol}$$, $$\mathrm{Cl} = 35.45\ \mathrm{g/mol})$$

Accepted Answer

$$29.2\ \mathrm{g}$$

Question 11

Which of the following best describes a homogeneous mixture?

Accepted Answer

A mixture with uniform composition throughout, such as salt water.

Question 12

Which of the following is the correct electron configuration for a neutral atom of sodium ($$Z=11$$)?

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^6$$\ $$3s^1$$

Question 13

A student needs to prepare 250.0 mL of a 0.100 M $$\mathrm{NaOH}$$ solution. How many grams of $$\mathrm{NaOH}$$ are required? ($$\mathrm{NaOH}$$ molar mass = $$40.00\ \mathrm{g/mol})$$

Accepted Answer

$$1.00\ \mathrm{g}$$

Question 14

Which of the following is an example of an exact number?

Accepted Answer

There are 12 eggs in a dozen.

Question 15

Which of the following elements is a halogen?

Accepted Answer

Chlorine

Question 16

A sample of glucose ($$\mathrm{C_6H_{12}O_6$}) $$contains $$3.01 	imes 10$$^{23}$$ molecules. How many moles of glucose are present?

Accepted Answer

$$0.500\ \mathrm{mol}$$

Question 17

Which of the following best describes the law of definite proportions?

Accepted Answer

A chemical compound always contains the same elements in the same proportion by mass.

Question 18

Which of the following is the correct percent composition by mass of oxygen in water ($$\mathrm{H_2O}$$)? ($$\mathrm{H} = 1.01\ \mathrm{g/mol}$$, $$\mathrm{O} = 16.00\ \mathrm{g/mol})$$

Accepted Answer

$$88.8\%$$

Question 19

Which of the following ions is isoelectronic with neon ($$\mathrm{Ne}$$)?

Accepted Answer

$$\mathrm{F^-}$$

Question 20

A 5.00 g sample of a compound contains 2.00 g of nitrogen. What is the percent by mass of nitrogen in the compound?

Accepted Answer

$$40.0\%$$

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

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