Q: A sample contains 3.0 moles of oxygen gas ($$O_2). $$How many molecules of $$O_2$$ are present in the sample?

$$1.81 \times 10$$^{24}$$ molecules

Question 1

Which of the following best describes the difference between a physical and a chemical property of matter?

Accepted Answer

A physical property can be observed without changing the identity of the substance, while a chemical property describes the substance's ability to undergo chemical changes.

Question 2

Which of the following is the correct scientific notation for the number 0.00056?

Accepted Answer

$$5.6 	imes 10$$^{-5}$$

Question 3

A student measures the mass of a sample as 12.345 g. How many significant figures are in this measurement?

Accepted Answer

5

Question 4

Which of the following elements is a noble gas?

Accepted Answer

Neon

Question 5

What is the correct formula for an ionic compound formed between magnesium and chlorine?

Accepted Answer

$$\mathrm{$$MgCl_2$$}$$

Question 6

Which of the following best explains why water is a polar molecule?

Accepted Answer

Water has a bent molecular shape and the oxygen atom is more electronegative than hydrogen, creating a dipole.

Question 7

A chemical reaction is classified as a combustion reaction if it:

Accepted Answer

Produces water and carbon dioxide from a hydrocarbon and oxygen.

Question 8

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

Accepted Answer

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

Question 9

If a solution contains 0.5 moles of NaCl dissolved in 1.0 L of water, what is the molarity of the solution?

Accepted Answer

$$0.5\ \mathrm{M}$$

Question 10

Which of the following statements about acids and bases is correct according to the Brønsted-Lowry theory?

Accepted Answer

An acid is a substance that donates a proton, and a base is a substance that accepts a proton.

Question 11

Which of the following is the correct formula for calculating the pressure of a gas using the ideal gas law?

Accepted Answer

$$P = \frac{nRT}{V}$$

Question 12

A radioactive isotope undergoes alpha decay. What particle is emitted?

Accepted Answer

A helium nucleus ($$^4_2\mathrm{He})$$

Question 13

Which of the following best describes the role of buffers in maintaining the pH of a solution?

Accepted Answer

Buffers prevent drastic changes in pH by neutralizing added acids or bases.

Question 14

Which of the following is a correct statement about the periodic trends in atomic radius?

Accepted Answer

Atomic radius increases down a group and decreases across a period from left to right.

Question 15

A sample contains 3.0 moles of oxygen gas ($$O_2). $$How many molecules of $$O_2$$ are present in the sample?

Accepted Answer

$$1.81 	imes 10$$^{24}$$ molecules

Question 16

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

Accepted Answer

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

Question 17

Which of the following best describes the intermolecular forces present in liquid water?

Accepted Answer

Hydrogen bonding and dipole-dipole interactions

Question 18

A solution is prepared by dissolving 10.0 g of NaOH in enough water to make 500 mL of solution. What is the molarity of the solution? ($$\mathrm{NaOH}$$ molar mass = 40.0 g/mol)

Accepted Answer

$$0.50\ \mathrm{M}$$

Question 19

Which of the following statements is true about the concept of partial pressure in a mixture of gases?

Accepted Answer

The partial pressure of a gas is the pressure it would exert if it occupied the entire volume alone at the same temperature.

Introductory Chemistry I (CHEM-1405) Syllabus & Study Guide

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