Q: Which experiment led to the determination of the charge of a single electron, and what was the fundamental charge found?

Millikan's oil drop experiment; $$-1.60 \times 10$$^{-19}$$ C

Q: A sample contains two isotopes of element X: 70% $$^{35}X ($$mass = 34.97 amu) and 30% $$^{37}X ($$mass = 36.97 amu). What is the atomic mass of element X?

$$0.70 \times 34.97 + 0.30 \times 36.97 = 35.57$$ amu

Q: How many atoms are in 0.50 mol of carbon?

$$0.50 \times 6.022 \times 10$$^{23}$$ = 3.011 \times 10$$^{23}$$ atoms

Question 1

Which experiment led to the determination of the charge of a single electron, and what was the fundamental charge found?

Accepted Answer

Millikan's oil drop experiment; $$-1.60 	imes 10$$^{-19}$$ C

Question 2

According to Dalton’s atomic theory, which statement is INCORRECT?

Accepted Answer

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

Question 3

A sample contains two isotopes of element X: 70% $$^{35}X ($$mass = 34.97 amu) and 30% $$^{37}X ($$mass = 36.97 amu). What is the atomic mass of element X?

Accepted Answer

$$0.70 	imes 34.97 + 0.30 	imes 36.97 = 35.57$$ amu

Question 4

Which law states that in a chemical reaction, matter is neither created nor destroyed?

Accepted Answer

Law of conservation of mass

Question 5

Which of the following best describes a homogeneous mixture?

Accepted Answer

A mixture with uniform composition throughout, such as sweetened tea.

Question 6

Which experiment disproved the plum-pudding model of the atom?

Accepted Answer

Rutherford’s gold foil experiment

Question 7

A neutral atom of magnesium has an atomic number of 12 and a mass number of 24. How many protons, neutrons, and electrons does it have?

Accepted Answer

12 protons, 12 neutrons, 12 electrons

Question 8

Which of the following is a compound?

Accepted Answer

Water ($$H_2O)$$

Question 9

How many atoms are in 0.50 mol of carbon?

Accepted Answer

$$0.50 	imes 6.022 	imes 10$$^{23}$$ = 3.011 	imes 10$$^{23}$$ atoms

Question 10

Which statement about the structure of the atom is correct according to the nuclear model?

Accepted Answer

Most of the atom’s mass is concentrated in a small, dense nucleus.

Question 11

A sample of copper has a mass of 12.7 g. How many moles of copper does it contain? (Molar mass of Cu = 63.55 g/mol)

Accepted Answer

$$\frac{12.7}{63.55} = 0.200$$ mol

Question 12

Which of the following is an example of a heterogeneous mixture?

Accepted Answer

Wet sand

Question 13

Which law explains why the ratio of oxygen to carbon in $$CO_2$$ and $$CO is a $$small whole number?

Accepted Answer

Law of multiple proportions

Question 14

Which subatomic particle determines the identity of an element?

Accepted Answer

Proton

Question 15

A neutral atom of chlorine has 17 protons and 18 neutrons. What is its mass number and isotope symbol?

Accepted Answer

Mass number = 35; Symbol: $$^{35}_{17}Cl$$

Question 16

Which of the following statements about isotopes is TRUE?

Accepted Answer

Isotopes of an element have the same number of protons but different numbers of neutrons.

Question 17

Which of the following best describes 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 18

How many atoms are in a 3.10 g sample of copper? (Molar mass of Cu = 63.55 g/mol, Avogadro’s number = $$6.022 	imes 10$$^{23}$$)

Accepted Answer

$$\frac{3.10}{63.55} 	imes 6.022 	imes 10$$^{23}$$ = 2.94 	imes 10$$^{22}$$ atoms

Question 19

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

Accepted Answer

Atoms are composed of protons, neutrons, and electrons.

Atoms: Structure, Theories, and Quantitative Concepts

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