Q: A sample contains $$2.45$$ mol of copper. How many copper atoms are present? (Avogadro’s number = $$6.022 \times 10$$^{23}$$)

$$1.47 \times 10$$^{24}$$ atoms

Question 1

Which of the following best describes the difference between a compound and a mixture?

Accepted Answer

A compound is made of two or more elements in fixed, definite proportions, while a mixture is composed of two or more substances in variable proportions.

Question 2

Which of the following statements about the law of conservation of mass is correct?

Accepted Answer

In a chemical reaction, the total mass of the substances involved does not change.

Question 3

A sample of ammonia contains 10.0 g of hydrogen. Given the nitrogen-to-hydrogen mass ratio in ammonia is 4.7:1, how many grams of nitrogen are present?

Accepted Answer

$$4.7 	imes 10 = 47 g$$

Question 4

Which experiment provided evidence for the existence of the nucleus in the atom?

Accepted Answer

Rutherford's gold foil experiment

Question 5

Which of the following is a homogeneous mixture?

Accepted Answer

Sweetened tea

Question 6

How many electrons are in an $$\mathrm{O}^{2-}$$ ion?

Accepted Answer

$$10$$

Question 7

Which statement best explains the difference between a scientific law and a scientific theory?

Accepted Answer

A law summarizes a series of related observations, while a theory gives the underlying reasons for them.

Question 8

A neutral atom of chlorine has an atomic number of 17 and a mass number of 35. How many neutrons does it have?

Accepted Answer

$$35 - 17 = 18$$ neutrons

Question 9

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

Accepted Answer

Atoms of one element can change into atoms of another element during chemical reactions.

Question 10

Which element contains 50 protons in its nucleus?

Accepted Answer

Tin

Question 11

A titanium cube contains $$2.86 	imes 10$$^{23}$$ atoms. The density of titanium is 4.50$$ \ \mathrm{$$g/cm^3$$}$$. What is the edge length of the cube in cm? (Atomic mass of Ti = 47.87 g/mol, Avogadro’s number = 6.022$$ 	imes $$10^{23})$$

Accepted Answer

$$0.400 cm$$

Question 12

Which of the following best describes an isotope?

Accepted Answer

Atoms of the same element with different numbers of neutrons

Question 13

Which of the following is the most abundant element on the surface of the Earth?

Accepted Answer

Oxygen

Question 14

A sample contains $$2.45$$ mol of copper. How many copper atoms are present? (Avogadro’s number = $$6.022 	imes 10$$^{23}$$)

Accepted Answer

$$1.47 	imes 10$$^{24}$$ atoms

Question 15

Which of the following is a correct representation of the isotope with 17 protons and 18 neutrons?

Accepted Answer

$$^{35}_{17}\mathrm{Cl}$$

Question 16

Which law states that all samples of a given compound have the same proportions of their constituent elements?

Accepted Answer

Law of definite proportions

Question 17

A neutral atom has 9 protons, 10 neutrons, and 10 electrons. What is its charge and what element is it?

Accepted Answer

It is a fluoride ion ($$\mathrm{F}^-) $$with a charge of $$-1.$$

Question 18

Which of the following best describes the result of J.J. Thomson’s cathode ray experiment?

Accepted Answer

Discovery of the electron as a negatively charged, low-mass particle present in all atoms.

Question 19

Which sample contains the most atoms: 1 g of copper, 1 g of carbon, or 1 g of uranium?

Accepted Answer

1 g of carbon

Question 20

Calculate the atomic mass of chlorine given the following data: $$75.77\%$$ chlorine-35 (mass $$34.97$$ amu) and $$24.23\%$$ chlorine-37 (mass $$36.97$$ amu).

Accepted Answer

$$35.45$$ amu

Atoms, Matter, and the Foundations of Chemistry: Chapter 1 Study Notes

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