Q: A sample contains 2.45 mol of copper. How many copper atoms are present in the sample?

$2.45 \times 6.022 \times 10^{23} = 1.48 \times 10^{24}$ atoms

Q: Calculate the atomic mass of copper given the following data: Cu-63 (69.17% abundance, mass = 62.9296 amu), Cu-65 (30.83% abundance, mass = 64.9278 amu).

$(0.6917 \times 62.9296) + (0.3083 \times 64.9278) = 63.55$ amu

Question 1

Which statement best explains why water has a higher boiling point than expected for its molecular mass?

Accepted Answer

Water molecules have strong hydrogen bonding due to their bent structure.

Question 2

According to Dalton's atomic theory, which statement is FALSE?

Accepted Answer

Atoms are created and destroyed during chemical reactions.

Question 3

A sample contains 2.45 mol of copper. How many copper atoms are present in the sample?

Accepted Answer

$2.45 	imes 6.022 	imes 10^{23} = 1.48 	imes 10^{24}$ atoms

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

A neutral atom of fluorine has 9 protons and 9 electrons. What is the charge and electron count of the F$^-$ ion?

Accepted Answer

Charge: $-1$, Electrons: 10

Question 6

Which of the following is a heterogeneous mixture?

Accepted Answer

Wet sand

Question 7

A sample of carbon monoxide (CO) contains 12 g of carbon and 16 g of oxygen. What is the mass ratio of oxygen to carbon in CO?

Accepted Answer

$\frac{16}{12} = 1.33:1$

Question 8

Which experiment led to the discovery of the electron?

Accepted Answer

Thomson's cathode ray experiment

Question 9

What is the atomic number and mass number of an isotope of chlorine with 17 protons and 18 neutrons?

Accepted Answer

Atomic number: 17, Mass number: 35

Question 10

Which statement about isotopes is TRUE?

Accepted Answer

Isotopes of an element have different numbers of neutrons.

Question 11

Calculate the atomic mass of copper given the following data: Cu-63 (69.17% abundance, mass = 62.9296 amu), Cu-65 (30.83% abundance, mass = 64.9278 amu).

Accepted Answer

$(0.6917 	imes 62.9296) + (0.3083 	imes 64.9278) = 63.55$ amu

Question 12

Which of the following best describes a pure substance?

Accepted Answer

A material composed of only one type of particle.

Question 13

Which property is used to classify matter as a solid, liquid, or gas?

Accepted Answer

The relative positions and interactions of the particles.

Question 14

A titanium cube contains $2.88 	imes 10^{22}$ atoms and has a density of $4.50 	ext{ g/cm}^3$. What is the first step to find the edge length of the cube?

Accepted Answer

Convert the number of atoms to moles using Avogadro's number.

Question 15

Which statement about the nucleus of an atom is CORRECT?

Accepted Answer

The nucleus contains most of the atom's mass.

Question 16

Which of the following is the correct formula for converting grams to moles?

Accepted Answer

$	ext{moles} = \frac{	ext{grams}}{	ext{molar mass}}$

Question 17

Which of the following best describes the law of multiple proportions?

Accepted Answer

When two elements form different compounds, the masses of one element that combine with a fixed mass of the other are in ratios of small whole numbers.

Question 18

Which subatomic particle has a mass of $1.673 	imes 10^{-24}$ g and no charge?

Accepted Answer

Neutron

Question 19

A sample of magnesium contains 78.99% Mg-24 (mass = 23.985 amu), 10.00% Mg-25 (mass = 24.986 amu), and 11.01% Mg-26 (mass = 25.983 amu). What is the atomic mass of magnesium?

Accepted Answer

$(0.7899 	imes 23.985) + (0.1000 	imes 24.986) + (0.1101 	imes 25.983) = 24.31$ amu

Chapter 1: Atoms

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