Q: How do you calculate the average atomic mass of an element with two isotopes, A and B, with masses $$m_A$$ and $$m_B$$ and abundances $$a_A$$ and $$a_B$$?

$$\text{Average atomic mass} = m_A \times a_A + m_B \times a_B$$

Question 1

Which statement best describes the Law of Conservation of Mass as it applies to a chemical reaction in a closed system?

Accepted Answer

Atoms are rearranged, but the total mass remains constant because atoms are not created or destroyed.

Question 2

According to Dalton's Atomic Theory, which of the following statements is FALSE?

Accepted Answer

Atoms of the same element can have different numbers of protons.

Question 3

A sample contains two elements, X and Y, that can combine to form two different compounds. In one compound, 10 g of X combines with 20 g of Y. In the other, 10 g of X combines with 40 g of Y. Which law does this illustrate?

Accepted Answer

Law of Multiple Proportions

Question 4

Which of the following correctly matches the subatomic particle with its charge and typical location in the atom?

Accepted Answer

Electron, negative, outside the nucleus

Question 5

An isotope of bromine is represented as $$\mathrm{^{80}_{35}Br}. $$What does the number 80 represent?

Accepted Answer

The sum of protons and neutrons in the nucleus

Question 6

How do you calculate the average atomic mass of an element with two isotopes, A and B, with masses $$m_A$$ and $$m_B$$ and abundances $$a_A$$ and $$a_B$$?

Accepted Answer

$$	ext{Average atomic mass} = m_A 	imes a_A + m_B 	imes a_B$$

Question 7

Which of the following best describes a metalloid?

Accepted Answer

An element with properties of both metals and nonmetals

Question 8

Which of the following elements exists naturally as a diatomic molecule?

Accepted Answer

Chlorine

Question 9

What is the empirical formula for a compound with a molecular formula of $$C_6H_{12}O_6$?

Accepted Answer

$$CH_2O$$

Question 10

Which of the following best describes a polyatomic ion?

Accepted Answer

A group of two or more atoms bonded together that have a net electric charge

Question 11

Predict the ionic charge of an oxygen atom based on its position in the periodic table.

Accepted Answer

$$-2$$

Question 12

Which of the following is the correct chemical formula for calcium bicarbonate?

Accepted Answer

$$\mathrm{Ca($$HCO_3$$)_2}$$

Question 13

What is the name of the molecular compound $$N_2O_3$$?

Accepted Answer

Dinitrogen trioxide

Question 14

Which of the following best describes the difference between a molecular and an empirical formula?

Accepted Answer

A molecular formula shows the exact number of atoms, while an empirical formula shows the simplest whole number ratio.

Question 15

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

Accepted Answer

Elements are arranged by increasing atomic number.

Question 16

Which of the following is a property of metals as seen on the periodic table?

Accepted Answer

They are located to the left of the staircase and tend to lose electrons.

Question 17

What is the correct name for $$H_2SO_4$$ when named as an acid?

Accepted Answer

Sulfuric acid

Question 18

Which of the following best describes a molecular compound?

Accepted Answer

Two or more nonmetals form together through covalent bonds (sharing electrons)

Question 19

Which of the following is the correct formula for sodium hydroxide?

Accepted Answer

$$\mathrm{NaOH}$$

Question 20

If a neutral atom of lithium loses one electron, what is the resulting ion and its charge?

Accepted Answer

$$\mathrm{Li^+}$$, with a charge of $$+1$$

Fundamental Concepts in General Chemistry: Atomic Theory, Periodic Table, and Chemical Formulas

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