Question 1

Which of the following statements best describes the difference between an element and a compound?

Accepted Answer

A compound consists of two or more elements chemically combined in a fixed ratio, while an element contains only one type of atom.

Question 2

A patient is prescribed 0.25 g of a medication. How many milligrams (mg) is this dose? (Use $$1 \ \mathrm{g} = 1000 \ \mathrm{mg})$$

Accepted Answer

$$250 \ \mathrm{mg}$$

Question 3

Which of the following best describes the trend in electronegativity across a period in the periodic table?

Accepted Answer

Electronegativity increases from left to right across a period.

Question 4

Which of the following represents a chemical change?

Accepted Answer

Rusting of iron

Question 5

How many protons, neutrons, and electrons are in the isotope $$^{37}\mathrm{Cl}$$?

Accepted Answer

Protons: 17, Neutrons: 20, Electrons: 17

Question 6

A sample of a radioisotope has a half-life of 4 hours. If you start with 80 mg, how much remains after 12 hours?

Accepted Answer

$$10 \ \mathrm{mg}$$

Question 7

Which of the following compounds contains both ionic and covalent bonds?

Accepted Answer

$$\mathrm{NH_4NO_3}$$

Question 8

What is the correct name for the compound $$\mathrm{Ca(NO_3$)_2}$$?

Accepted Answer

Calcium nitrate

Question 9

Which of the following molecules is nonpolar, based on its molecular shape and bond polarity?

Accepted Answer

$$\mathrm{CO_2$}$$

Question 10

A solution contains $$15.0 \ \mathrm{g} of $$NaCl dissolved in $$150.0 \ \mathrm{g} of $$water. What is the percent by mass of NaCl in the solution?

Accepted Answer

$$10.0\%$$

Question 11

Which of the following is the correct Lewis structure for methane ($$\mathrm{CH_4$}$$)?

Accepted Answer

A central C atom with four single bonds to four H atoms, no lone pairs on C.

Question 12

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

Accepted Answer

$$\mathrm{Na^+}$$

Question 13

A sample of metal has a mass of $$27.0 \ \mathrm{g}$$ and a volume of $$3.00 \ \mathrm{cm^3$}. $$What is its density?

Accepted Answer

$$9.00 \ \mathrm{g/cm^3$}$$

Question 14

Which of the following best describes the difference between accuracy and precision?

Accepted Answer

Accuracy is how close measurements are to the true value; precision is how close measurements are to each other.

Question 15

Which of the following is the correct formula for ammonium sulfate?

Accepted Answer

$$\mathrm{(NH_4$)_2SO_4}$$

Question 16

Which of the following is a correct balanced equation for the reaction of sodium with chlorine gas to form sodium chloride?

Accepted Answer

$$2\mathrm{Na} + \mathrm{Cl_2$} \rightarrow 2\mathrm{NaCl}$$

Question 17

Which of the following molecules has a trigonal pyramidal molecular shape according to VSEPR theory?

Accepted Answer

$$\mathrm{NH_3$}$$

Question 18

Convert $$5.00$$ miles to kilometers. (Given: $$1 \ \mathrm{mile} = 1609 \ \mathrm{meters}$$, $$1 \ \mathrm{km} = 1000 \ \mathrm{meters})$$

Accepted Answer

$$8.05 \ \mathrm{km}$$

Question 19

Which of the following is an example of an allotrope?

Accepted Answer

Ozone ($$\mathrm{O_3$}) $$and oxygen gas ($$\mathrm{O_2$})$$

Question 20

Which of the following statements about polyatomic ions is correct?

Accepted Answer

Polyatomic ions contain two or more atoms covalently bonded, carrying a net charge.

CHEM 103 Study Guide: Chapters 1–3 (Matter, Measurement, Atoms, Compounds)

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