Question 1

Which of the following statements best describes the difference between a physical change and a chemical change?

Accepted Answer

A chemical change results in the formation of new substances, while a physical change does not alter the chemical identity.

Question 2

A sample of a gas occupies $$2.50\ \mathrm{L} at$$ $$1.00\ \mathrm{atm}$$ and $$300\ \mathrm{K}. $$What will be its volume at $$2.00\ \mathrm{atm}$$ and $$300\ \mathrm{K}$$, assuming ideal gas behavior?

Accepted Answer

$$1.25\ \mathrm{L}$$

Question 3

Which of the following best explains why water is a liquid at room temperature while methane ($$\mathrm{CH_4$}) is a $$gas, even though both are small molecules?

Accepted Answer

Water molecules have stronger hydrogen bonding than methane molecules.

Question 4

Which of the following is the correct electron configuration for a neutral atom of sodium ($$\mathrm{Na}$$, atomic number 11)?

Accepted Answer

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

Question 5

A solution is prepared by dissolving $$10.0\ \mathrm{g} of $$sodium chloride ($$\mathrm{NaCl}) in $$enough water to make $$500.0\ \mathrm{mL} of $$solution. What is the molarity of the solution? ($$\mathrm{NaCl}$$ molar mass = $$58.44\ \mathrm{g/mol})$$

Accepted Answer

$$0.342\ \mathrm{M}$$

Question 6

Which of the following best describes the role of a buffer solution in the human bloodstream?

Accepted Answer

It maintains a constant pH by neutralizing small amounts of added acid or base.

Question 7

Which of the following is the correct balanced chemical equation for the combustion of propane ($$\mathrm{C_3H_8}) in $$oxygen?

Accepted Answer

$$\mathrm{C_3H_8} + 5\ \mathrm{O_2$} \rightarrow 3\ \mathrm{CO_2$} + 4\ \mathrm{H_2O}$$

Question 8

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 9

A $$25.0\ \mathrm{mL}$$ sample of $$0.200\ \mathrm{M}$$ hydrochloric acid ($$\mathrm{HCl}) is $$titrated with $$0.100\ \mathrm{M}$$ sodium hydroxide ($$\mathrm{NaOH}). $$What volume of $$\mathrm{NaOH} is $$required to reach the equivalence point?

Accepted Answer

$$50.0\ \mathrm{mL}$$

Question 10

Which of the following best describes the trend in atomic radius as you move from left to right across a period in the periodic table?

Accepted Answer

Atomic radius decreases due to increasing nuclear charge.

Question 11

A radioactive isotope has a half-life of $$3.0\ \mathrm{hours}. If $$you start with $$80.0\ \mathrm{g}$$, how much remains after $$9.0\ \mathrm{hours}$$?

Accepted Answer

$$10.0\ \mathrm{g}$$

Question 12

Which of the following is a correct statement about acids according to the Brønsted-Lowry theory?

Accepted Answer

An acid is a substance that donates a proton ($$\mathrm{H^+}) to $$another substance.

Question 13

Which of the following best explains why ionic compounds tend to have high melting points?

Accepted Answer

Strong electrostatic forces hold the ions together in a lattice structure.

Question 14

A sample of aluminum has a mass of $$13.5\ \mathrm{g}. $$How many moles of aluminum are present? (Molar mass of Al = $$26.98\ \mathrm{g/mol})$$

Accepted Answer

$$0.500\ \mathrm{mol}$$

Question 15

Which of the following is the correct Lewis structure for carbon dioxide ($$\mathrm{CO_2$}$$)?

Accepted Answer

O=C=O, with each oxygen atom having two lone pairs

Question 16

Which of the following best describes the process of oxidation in a redox reaction?

Accepted Answer

Oxidation is the loss of electrons by a substance.

Question 17

A patient receives a $$100.0\ \mathrm{mL}$$ intravenous solution containing $$0.90\ \mathrm{g} of $$sodium chloride ($$\mathrm{NaCl}). $$What is the concentration in $$\mathrm{g/L}$$?

Accepted Answer

$$9.0\ \mathrm{g/L}$$

Question 18

Which of the following best describes the VSEPR theory prediction for the shape of methane ($$\mathrm{CH_4$}$$)?

Accepted Answer

Tetrahedral

Question 19

Which of the following is a correct statement about Avogadro’s number?

Accepted Answer

It is the number of particles in one mole, $$6.022 	imes 10$$^{23}$$.

Introductory Chemistry I: Course Structure, Topics, and Expectations

Guida di studio - Domande di pratica

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