Q: A sample contains 0.250 mol of water molecules. How many molecules are present in the sample? (Avogadro's number $$N_A = 6.022 \times 10$$^{23}$$ mol$$^{-1}$$)

$$1.51 \times 10$$^{23}$$ molecules

Question 1

A sample of gold has a mass of 19.3 g and occupies a volume of 1.00 cm$$^3. $$What is the density of gold in kg/m$$^3$$? (1 cm$$^3$$ = $$1 	imes 10$$^{-6}$$ m^3$)

Accepted Answer

$$1.93 	imes 10^4$ kg/m^3$

Question 2

Which of the following best describes the difference between precision and accuracy in a set of measurements?

Accepted Answer

Precision refers to how close measurements are to each other, while accuracy refers to how close measurements are to the true value.

Question 3

A student records the mass of a sample as 0.02030 g. How many significant figures does this measurement have?

Accepted Answer

5

Question 4

Which of the following is an example of an intensive property?

Accepted Answer

Density

Question 5

Which of the following best explains why the Aristotle model of matter (earth, air, fire, water) was replaced?

Accepted Answer

It could not explain the conservation of mass observed in chemical reactions.

Question 6

A neutral atom of $$^{35}_{17}Cl $$has:

Accepted Answer

17 protons, 18 neutrons, 17 electrons

Question 7

Which experiment led to the conclusion that atoms are mostly empty space with a small, dense nucleus?

Accepted Answer

Rutherford's gold foil experiment

Question 8

A sample contains 0.250 mol of water molecules. How many molecules are present in the sample? (Avogadro's number $$N_A = 6.022 	imes 10$$^{23}$$ mol$$^{-1}$$)

Accepted Answer

$$1.51 	imes 10$$^{23}$$ molecules

Question 9

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 10

The atomic weight of chlorine is approximately 35.5. If the two main isotopes are $$^{35}Cl (75.8$$%) and $$^{37}Cl (24.2$$%), what is the best explanation for the atomic weight?

Accepted Answer

It is a weighted average of the masses of $$^{35}Cl $$and $$^{37}Cl $$based on their natural abundances.

Question 11

Which of the following best describes the photoelectric effect?

Accepted Answer

Electrons are ejected from a metal surface when light of sufficient frequency shines on it.

Question 12

What is the energy of a photon with a wavelength of 400 nm? (Planck's constant $$h = 6.63 	imes 10$$^{-34}$$ J·s, speed of light c = 2.998$$ 	imes $$10^8 m/s)$$

Accepted Answer

$$4.97 	imes 10$$^{-19}$$ J

Question 13

Which of the following sets of quantum numbers is NOT allowed for an electron in an atom?

Accepted Answer

$$n=2,\ l=2,\ m_l=0,\ m_s=+\frac{1}{2}$$

Question 14

How many d orbitals are present in the $$n=3$$ shell?

Accepted Answer

5

Question 15

Which of the following best describes Hund's rule as applied to orbital box diagrams?

Accepted Answer

Electrons fill degenerate orbitals singly before pairing up.

Question 16

Which element is most likely to form a $$2+$$ cation based on its position in the periodic table?

Accepted Answer

Magnesium (Mg)

Question 17

Which of the following statements about effective nuclear charge ($$Z_{	ext{eff}}) is $$correct?

Accepted Answer

$$Z_{	ext{eff}}$$ increases from left to right across a period.

Question 18

Which of the following ions is largest in size?

Accepted Answer

O$$^{2-}$$

Question 19

Which of the following best describes the uncertainty principle?

Accepted Answer

It is impossible to simultaneously know both the exact position and momentum of an electron.

Question 20

A sample of CO$$_2$$ has a mass of 44.0 g. How many molecules of CO$$_2$$ are present in the sample? (Molar mass of CO$$_2 = 44.0 g/$$mol, $$N_A = 6.022 	imes 10$$^{23}$$ mol$$^{-1}$$)

Accepted Answer

$$6.022 	imes 10$$^{23}$$ molecules

General Chemistry Study Guide: Chapters E, 1, 2, and 3

Guida di studio - Domande di pratica

Study guide - Flashcard