Q: How many atoms are present in 2 moles of carbon?

$$2 \times 6.022 \times 10$$^{23}$$

Question 1

Which scientific law is best demonstrated by the reaction: 100.00 grams of mercuric oxide decomposes to form 92.61 grams of mercury and 7.39 grams of oxygen?

Accepted Answer

Law of conservation of mass

Question 2

A sample of lead reacts with sulfur to form lead sulfide. If 10.00 g of lead reacts with 1.55 g of sulfur to form 11.55 g of lead sulfide, what will happen if 10.00 g of lead is reacted with 3.00 g of sulfur?

Accepted Answer

Only 1.55 g of sulfur will react, and 1.45 g of sulfur will remain unreacted.

Question 3

Which of the following statements is NOT a postulate of Dalton’s atomic theory?

Accepted Answer

Atoms are created and destroyed in chemical reactions.

Question 4

A green mineral sample is found to always contain 57.48% Cu, 5.43% C, 0.91% H, and 36.18% O by mass, regardless of its source. Which law does this observation support?

Accepted Answer

Law of definite proportions

Question 5

If 18.00 g of lead reacts with 1.55 g of sulfur, forming 11.55 g of lead sulfide and leaving 8.00 g of lead unreacted, what is the limiting reactant?

Accepted Answer

Sulfur

Question 6

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

Accepted Answer

Rutherford’s gold foil experiment

Question 7

Which type of radiation is not deflected by electric or magnetic fields and is the most penetrating?

Accepted Answer

Gamma (γ) rays

Question 8

How many atoms are present in 2 moles of carbon?

Accepted Answer

$$2 	imes 6.022 	imes 10$$^{23}$$

Question 9

What is the electron configuration for an atom of oxygen (atomic number 8)?

Accepted Answer

$$1s^2$$ $$2s^2$$ $$2p^4$$

Question 10

Which of the following best describes an isotope?

Accepted Answer

Atoms with the same number of protons but different numbers of neutrons

Question 11

According to the Bohr model, what happens when an electron in an atom absorbs a quantum of energy?

Accepted Answer

It moves to a higher energy level

Question 12

Which of the following is the correct order for filling electron subshells according to the Aufbau principle?

Accepted Answer

$$1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p$$

Question 13

A certain element has an atomic number of 11. How many protons, neutrons, and electrons are present in its most common isotope, sodium-23?

Accepted Answer

11 protons, 12 neutrons, 11 electrons

Question 14

Which of the following best explains why the periodic table is organized into groups and periods?

Accepted Answer

Groups contain elements with similar chemical properties due to similar valence electron configurations.

Question 15

If a chemical reaction starts with 6 oxygen atoms and 4 hydrogen atoms (total mass: 100), and ends with 6 oxygen atoms and 4 hydrogen atoms in new molecules, what law does this illustrate?

Accepted Answer

Law of conservation of mass

Question 16

Which of the following statements about orbitals is correct?

Accepted Answer

Each orbital can hold a maximum of 2 electrons.

Question 17

A sample of water contains 5 moles. How many molecules of water are present in the sample?

Accepted Answer

$$5 	imes 6.022 	imes 10$$^{23}$$

Question 18

Which scientist is credited with the discovery of the electron?

Accepted Answer

J.J. Thomson

Question 19

Which of the following best describes a cation?

Accepted Answer

An ion with a positive charge

Question 20

Which of the following is the correct electron configuration for sodium (Na, atomic number 11)?

Accepted Answer

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

Atoms and Atomic Structure: Fundamental Concepts for Introductory Chemistry

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