Q: Which of the following statements best describes the mole in chemistry?

A mole is a specific number, $6.022 \times 10^{23}$, that allows us to count atoms or molecules by weighing them.

Q: What is Avogadro's number and what does it represent?

$6.022 \times 10^{23}$, the number of atoms in 12 g of carbon-12

Question 1

Which of the following statements best describes the mole in chemistry?

Accepted Answer

A mole is a specific number, $6.022 	imes 10^{23}$, that allows us to count atoms or molecules by weighing them.

Question 2

If you have 0.58 g of pure carbon, how many moles of carbon do you have? (Atomic mass of C = 12.01 g/mol)

Accepted Answer

$4.8 	imes 10^{-2}$ mol

Question 3

How many atoms are in 16.2 g of aluminum? (Molar mass of Al = 26.98 g/mol, Avogadro's number $= 6.022 	imes 10^{23}$)

Accepted Answer

$3.62 	imes 10^{23}$ atoms

Question 4

What is the mass of 1.75 mol of water ($H_2O$)? (Atomic masses: H = 1.01 g/mol, O = 16.00 g/mol)

Accepted Answer

$31.5$ g

Question 5

A sample contains $4.78 	imes 10^{24}$ molecules of $NO_2$. What is its mass? (Molar mass of $NO_2 = 46.01$ g/mol)

Accepted Answer

$365$ g

Question 6

How many moles of oxygen atoms are present in 1.7 mol of $CaCO_3$?

Accepted Answer

$5.1$ mol

Question 7

Find the mass of sodium in 15 g of $NaCl$. (Molar mass of $NaCl = 58.44$ g/mol, Molar mass of Na = 22.99 g/mol)

Accepted Answer

$5.90$ g

Question 8

Which of the following is true about the relationship between atomic mass and molar mass?

Accepted Answer

The molar mass of an element in grams per mole is numerically equal to its atomic mass in amu.

Question 9

If the FDA recommends less than 2.3 g of sodium per day, how many grams of $NaCl$ can you consume and stay below this limit? (Molar mass of $NaCl = 58.44$ g/mol, Molar mass of Na = 22.99 g/mol)

Accepted Answer

$5.85$ g

Question 10

Which conversion factor would you use to convert from grams of a compound to moles of a constituent element?

Accepted Answer

Molar mass of the compound and the ratio of moles of element to moles of compound from the chemical formula.

Question 11

A chemist has $1.1 	imes 10^{22}$ silver atoms. How many moles of silver does this represent? ($1$ mol $= 6.022 	imes 10^{23}$ atoms)

Accepted Answer

$1.8 	imes 10^{-2}$ mol

Question 12

Which statement about chemical formulas is correct?

Accepted Answer

Chemical formulas indicate the relative number of each kind of element in a compound based on atoms or moles.

Question 13

What is Avogadro's number and what does it represent?

Accepted Answer

$6.022 	imes 10^{23}$, the number of atoms in 12 g of carbon-12

Question 14

Which of the following best explains why the mass of 1 mole of atoms changes for different elements?

Accepted Answer

Different elements have different atomic masses.

Question 15

How many moles of chlorine atoms are present in 1 mole of $CCl_4$?

Accepted Answer

4 moles

Question 16

A compound has an empirical formula of $CH_2O$ and a molar mass of 180 g/mol. What is its molecular formula?

Accepted Answer

$C_6H_{12}O_6$

Question 17

Which of the following is a correct conversion factor for the number of oxygen atoms in $CO_2$ molecules?

Accepted Answer

$2$ O atoms : $1$ CO$_2$ molecule

Question 18

If you have 3.5 mol of helium, how many helium atoms do you have?

Accepted Answer

$2.1 	imes 10^{24}$ atoms

Question 19

Which of the following is NOT a correct step in converting grams of a compound to grams of a constituent element?

Accepted Answer

Multiply grams of compound directly by Avogadro's number.

Chapter 6: Chemical Composition – Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards