Q: Which of the following best describes the concept of effective nuclear charge ($$Z_{\text{eff}}) $$and its trend across a period?

$$Z_{\text{eff}}$$ increases from left to right across a period because the number of protons increases while shielding remains relatively constant.

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 units of 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 statements best describes the difference between precision and accuracy?

Accepted Answer

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

Question 3

A student measures the mass of a sample as 0.00450 g. How many significant figures are in this measurement?

Accepted Answer

3

Question 4

Which of the following is an example of a chemical property?

Accepted Answer

Iron rusts when exposed to oxygen.

Question 5

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

Accepted Answer

Experiments showed that mass is conserved and substances can be broken down into elements, not just four basic types.

Question 6

A sample of magnesium contains $$2.41 	imes 10$$^{24}$$ atoms. How many moles of magnesium are present? (N_A = 6.022$$ 	imes $$10^{23}$$ mol$$^{-1})$$

Accepted Answer

4.00 mol

Question 7

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 8

Which of the following best describes the result of Rutherford's gold foil experiment?

Accepted Answer

Most alpha particles passed through, but some were deflected at large angles, indicating a small, dense, positively charged nucleus.

Question 9

A naturally occurring element has two isotopes: $$^{35}Cl ($$mass = 34.97 u, abundance = 75.8%) and $$^{37}Cl ($$mass = 36.97 u, abundance = 24.2%). What is the atomic weight of chlorine?

Accepted Answer

$$35.5 u$$

Question 10

Which of the following best describes the concept of effective nuclear charge ($$Z_{	ext{eff}}) $$and its trend across a period?

Accepted Answer

$$Z_{	ext{eff}}$$ increases from left to right across a period because the number of protons increases while shielding remains relatively constant.

Question 11

Which of the following ions is isoelectronic with Ne?

Accepted Answer

$$	ext{F}^-$$

Question 12

A photon has a wavelength of $$4.00 	imes 10$$^{-7}$$ m. What is its energy? (c = 2.998$$ 	imes $$10^8 m/s$$, $$h = 6.63 	imes 10$$^{-34}$$ J·s)

Accepted Answer

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

Question 13

Which of the following best describes the photoelectric effect?

Accepted Answer

Electrons are ejected from a metal surface only if the incident light has a frequency above a certain threshold, regardless of intensity.

Question 14

Which of the following statements about atomic size is correct?

Accepted Answer

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

Question 15

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

Accepted Answer

Electrons fill degenerate orbitals singly with parallel spins before pairing up.

Question 16

Which of the following is the correct electron configuration for the $$	ext{O}^{2-}$$ ion?

Accepted Answer

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

Question 17

Which of the following best describes the difference between an extensive and an intensive property?

Accepted Answer

An extensive property depends on the amount of substance, while an intensive property does not.

Question 18

Which of the following best explains why lithium and sodium have similar chemical properties?

Accepted Answer

They have the same number of valence electrons and similar electron configurations.

Question 19

A sample of carbon dioxide has a mass of 44.0 g. How many molecules of CO$$_2$$ are present? (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

Question 20

Which of the following best describes the uncertainty principle?

Accepted Answer

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

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

Guida di studio - Domande di pratica

Study guide - Flashcard