Q: Which of the following is the correct formula for calculating the number of neutrons in an atom?

$$\text{Number of neutrons} = A - Z$$

Q: Which of the following is the value of 1 atomic mass unit (amu) in grams?

$$1.66054 \times 10$$^{-24}$$ g

Question 1

Which of the following statements best describes Dalton's atomic theory as illustrated in the study materials?

Accepted Answer

Atoms of each element are identical in mass and properties, and compounds are formed by the combination of atoms of different elements in fixed ratios.

Question 2

Which law is demonstrated when a bottle of water, a fountain, ice cubes, and the ocean all contain H$$_2O $$with the same ratio of hydrogen to oxygen atoms?

Accepted Answer

Law of Constant Composition

Question 3

A sample of coal is burned in a closed system and its mass remains unchanged before and after the reaction. Which law does this observation support?

Accepted Answer

Law of Conservation of Mass

Question 4

Which of the following best explains the Law of Multiple Proportions using the compounds CO and CO$$_2$$?

Accepted Answer

The masses of oxygen that combine with a fixed mass of carbon in CO and CO$$_2$$ are in a simple whole number ratio.

Question 5

Which subatomic particle is responsible for the atomic number of an element?

Accepted Answer

Proton

Question 6

Given the isotope $$^{137}Ba$$, how many neutrons does it contain?

Accepted Answer

$$81$$

Question 7

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 8

Calculate the average atomic mass (atomic weight) of an element with two isotopes: 90% $$^{63}X ($$mass = 62.93 amu) and 10% $$^{65}X ($$mass = 64.93 amu).

Accepted Answer

$$63.19$$ amu

Question 9

Which of the following best describes the structure of an atom according to the modern atomic model?

Accepted Answer

Protons and neutrons are found in the nucleus, and electrons occupy the surrounding space.

Question 10

If a neutral atom of gold ($$^{197}Au) $$has an atomic number of 79, how many electrons does it have?

Accepted Answer

$$79$$

Question 11

Which of the following is the correct formula for calculating the number of neutrons in an atom?

Accepted Answer

$$	ext{Number of neutrons} = A - Z$$

Question 12

Which of the following best explains why the mass of an atom is concentrated in its nucleus?

Accepted Answer

The nucleus contains protons and neutrons, which have much greater mass than electrons.

Question 13

Which of the following is the value of 1 atomic mass unit (amu) in grams?

Accepted Answer

$$1.66054 	imes 10$$^{-24}$$ g

Question 14

A neutral atom of nickel ($$^{59}Ni) $$has how many protons, neutrons, and electrons?

Accepted Answer

28 protons, 31 neutrons, 28 electrons

Question 15

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

Accepted Answer

Atoms can be converted into other elements during chemical reactions.

Atoms, Molecules, and Ions: Foundations of Atomic Theory and Structure

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