Q: What is Avogadro's number, and what does it represent?

$$6.022 \times 10$$^{23}$$, the number of atoms in one mole of a substance

Question 1

Which scientific law states that during a chemical change, matter is neither created nor destroyed?

Accepted Answer

Law of Conservation of Mass

Question 2

A sample of water is decomposed into 75.5 g of oxygen and an unknown mass of hydrogen. If the initial mass of water was 85.0 g, what is the mass of hydrogen produced?

Accepted Answer

$$9.5\ \mathrm{g}$$

Question 3

Which statement best describes the Law of Definite Proportions?

Accepted Answer

A compound always contains the same elements in the same ratio by mass, regardless of its source.

Question 4

What is Avogadro's number, and what does it represent?

Accepted Answer

$$6.022 	imes 10$$^{23}$$, the number of atoms in one mole of a substance

Question 5

Calculate the number of moles in $$150.0\ \mathrm{g} of$$ $$CO_2. ($$Molar mass of $$CO_2 is$$ $$44.0\ \mathrm{g/mol})$$

Accepted Answer

$$3.41\ \mathrm{moles}$$

Question 6

Which subatomic particle has a mass of approximately $$1\ \mathrm{u}$$ and a positive charge?

Accepted Answer

Proton

Question 7

What is the atomic number and mass number of silicon ($$Si) as $$shown in the periodic table?

Accepted Answer

Atomic number: $$14$$, Mass number: $$28.085$$

Question 8

Which of the following best describes an isotope?

Accepted Answer

Atoms of the same element with different numbers of neutrons

Question 9

Carbon-14 undergoes beta decay. What happens during this process?

Accepted Answer

A neutron turns into a proton and an electron is emitted

Question 10

Which type of radioactive emission has no charge and is the most penetrating?

Accepted Answer

Gamma ray

Question 11

If a neutral atom loses one or more electrons, what type of ion does it become?

Accepted Answer

Cation

Question 12

Which of the following is the correct nuclear symbol for an oxygen atom with 8 protons and 10 neutrons?

Accepted Answer

$$^{18}_{8}O$$

Question 13

A soil particle attracts $$Ca^{2+}$$ ions. What is the likely charge on the soil particle?

Accepted Answer

Negative

Question 14

Which of the following best explains why the atomic mass of carbon is not exactly 12?

Accepted Answer

It is a weighted average of all naturally occurring isotopes of carbon

Question 15

What is the molar mass of water ($$H_2O$$)? (Atomic masses: $$H = 1.008$$, $$O = 15.999)$$

Accepted Answer

$$18.015\ \mathrm{g/mol}$$

Question 16

Which of the following is NOT a subatomic particle found in the nucleus?

Accepted Answer

Electron

Question 17

If you have $$2.00\ \mathrm{g} of $$diamond (pure carbon), how many moles of carbon do you have? (Atomic mass of C = $$12.011\ \mathrm{g/mol})$$

Accepted Answer

$$0.166\ \mathrm{mol}$$

Question 18

Which process is responsible for the formation of hydrogen ions in ocean acidification?

Accepted Answer

Carbonic acid dissociates in water

Question 19

Which of the following is true about cation retention in soils?

Accepted Answer

Positive-negative charges attract, helping retain cations on negatively charged soil particles

Question 20

Which of the following is a real-world application of radioactive isotopes?

Accepted Answer

Carbon-14 dating to determine the age of ancient artifacts

Atomic Structure, Matter, and Fundamental Chemical Laws: Study Notes for Introductory Chemistry

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