Q: A sample contains 22.5 g of $\mathrm{CO_2}$. How many molecules of $\mathrm{CO_2}$ are present? (Molar mass of $\mathrm{CO_2}$ = 44.01 g/mol, Avogadro's number = $6.022 \times 10^{23}$)

$3.08 \times 10^{23}$ molecules

Question 1

Which statement best describes the difference between an atom and an element?

Accepted Answer

An atom is the smallest identifiable unit of an element, while an element is a substance that cannot be broken down into simpler substances.

Question 2

According to Dalton's Atomic Theory, which of the following is NOT correct?

Accepted Answer

Atoms of a given element can have different masses.

Question 3

Which experiment led to the discovery of the atomic nucleus?

Accepted Answer

Rutherford's Gold Foil Experiment

Question 4

What is the charge and location of a neutron in an atom?

Accepted Answer

Neutral, located in the nucleus

Question 5

Which of the following best describes an isotope?

Accepted Answer

Atoms of the same element with different numbers of neutrons

Question 6

Which group on the periodic table contains elements that are highly unreactive?

Accepted Answer

Noble gases (Group 8A)

Question 7

A neutral atom of sodium (Na) has an atomic number of 11. How many electrons does it have?

Accepted Answer

11

Question 8

Which of the following is a property of metals?

Accepted Answer

Good conductors of heat and electricity

Question 9

What is the formula for the ionic compound formed between magnesium and oxygen?

Accepted Answer

$\mathrm{MgO}$

Question 10

Which of the following best describes a molecular compound?

Accepted Answer

A compound composed of two or more nonmetals

Question 11

What is the correct name for the compound $\mathrm{CO_2}$?

Accepted Answer

Carbon dioxide

Question 12

Which of the following is the correct formula for aluminum oxide?

Accepted Answer

$\mathrm{Al_2O_3}$

Question 13

How many atoms are in 2.00 moles of oxygen gas ($\mathrm{O_2}$)? (Avogadro's number = $6.022 	imes 10^{23}$)

Accepted Answer

$2.41 	imes 10^{24}$ atoms

Question 14

Which of the following is a polyatomic ion?

Accepted Answer

$\mathrm{NO_3^-}$

Question 15

What is the formula mass of water ($\mathrm{H_2O}$)? (H: 1.01 amu, O: 16.00 amu)

Accepted Answer

$18.02$ amu

Question 16

Which of the following best describes a cation?

Accepted Answer

A positively charged ion

Question 17

A sample contains 22.5 g of $\mathrm{CO_2}$. How many molecules of $\mathrm{CO_2}$ are present? (Molar mass of $\mathrm{CO_2}$ = 44.01 g/mol, Avogadro's number = $6.022 	imes 10^{23}$)

Accepted Answer

$3.08 	imes 10^{23}$ molecules

Question 18

Which of the following is the correct empirical formula for hydrogen peroxide ($\mathrm{H_2O_2}$)?

Accepted Answer

$\mathrm{HO}$

Question 19

Which of the following statements about the periodic table is correct?

Accepted Answer

Elements in the same group have similar chemical properties.

Question 20

What is the charge on the ion formed when chlorine gains one electron?

Accepted Answer

$-1$

Exam 2

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