Q: How many atoms are present in $$2.35 \times 10$$^{-3}$$ moles of gold ($$\mathrm{Au}$$)? (N_A = 6.022$$ \times $$10^{23}$$ atoms/mol)

$$1.41 \times 10$$^{21}$$ atoms

Q: How many atoms are in 16.5 g of nickel (Ni)? (Molar mass of Ni = 58.69 g/mol, $$N_A = 6.022 \times 10$$^{23}$$ atoms/mol)

$$1.69 \times 10$$^{23}$$ atoms

Question 1

Which law states that in a chemical reaction, matter is neither created nor destroyed, and who is credited with its discovery?

Accepted Answer

Law of Conservation of Mass, Antoine Lavoisier

Question 2

A sample of sodium reacts with chlorine gas to form sodium chloride. If 7.7 g of Na reacts with 11.9 g of Cl$$_2 to $$produce 19.6 g of NaCl, which law does this experiment demonstrate?

Accepted Answer

Law of Conservation of Mass

Question 3

Which of the following best describes the Law of Definite Proportions?

Accepted Answer

All samples of a given compound have the same proportions of their constituent elements.

Question 4

Carbon forms two oxides: CO and CO$$_2. If 1.0 g of $$carbon combines with 1.33 g of oxygen to form CO and with 2.66 g of oxygen to form CO$$_2$$, what law is illustrated by this data?

Accepted Answer

Law of Multiple Proportions

Question 5

Which postulate of Dalton’s Atomic Theory is no longer considered true due to the discovery of isotopes?

Accepted Answer

All atoms of a given element are identical in mass and properties.

Question 6

J.J. Thomson’s cathode ray tube experiment led to the discovery of which subatomic particle, and what property did he measure?

Accepted Answer

Electron, charge-to-mass ratio

Question 7

Millikan’s oil drop experiment determined the charge of the electron. What is the value of this charge?

Accepted Answer

$$-1.602 	imes 10$$^{-19}$$ C

Question 8

Which experiment disproved the 'plum pudding' model of the atom and led to the nuclear model?

Accepted Answer

Rutherford’s gold foil experiment

Question 9

Which subatomic particle was discovered by James Chadwick, and what is its charge?

Accepted Answer

Neutron, 0

Question 10

An atom has 17 protons, 18 neutrons, and 17 electrons. What is its chemical symbol using isotopic notation?

Accepted Answer

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

Question 11

Which of the following statements about isotopes is correct?

Accepted Answer

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

Question 12

Which scientist is credited with the first arrangement of the periodic table based on atomic mass and chemical properties?

Accepted Answer

Dmitri Mendeleev

Question 13

Which group of elements is characterized by being good conductors of heat and electricity, malleable, and ductile?

Accepted Answer

Metals

Question 14

A neutral atom of sodium (Na) has 11 protons. If it loses one electron, what is the resulting ion called and what is its charge?

Accepted Answer

Sodium ion, $$\mathrm{Na}^+$$

Question 15

Calculate the atomic mass of gallium if it is 60.11% Ga-69 (68.9256 amu) and 39.89% Ga-71 (70.9247 amu).

Accepted Answer

$$69.72$$ amu

Question 16

How many atoms are present in $$2.35 	imes 10$$^{-3}$$ moles of gold ($$\mathrm{Au}$$)? (N_A = 6.022$$ 	imes $$10^{23}$$ atoms/mol)

Accepted Answer

$$1.41 	imes 10$$^{21}$$ atoms

Question 17

What is the molar mass of carbon, and how is it used in chemical calculations?

Accepted Answer

$$12.01 g/$$mol; it is used to convert between grams and moles of carbon.

Question 18

A sample contains $$6.35 	imes 10$$^{23}$$ atoms of potassium. How many moles of potassium are present?

Accepted Answer

$$1.05$$ mol

Question 19

Which of the following best describes a cation?

Accepted Answer

A positively charged ion formed by the loss of electrons, usually from a metal.

Question 20

How many atoms are in 16.5 g of nickel (Ni)? (Molar mass of Ni = 58.69 g/mol, $$N_A = 6.022 	imes 10$$^{23}$$ atoms/mol)

Accepted Answer

$$1.69 	imes 10$$^{23}$$ atoms

Atoms and Elements: Foundations of Modern Atomic Theory

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