Q: Which of the following is a correct formula for converting between mass and moles?

$\text{moles} = \frac{\text{mass (g)}}{\text{molar mass (g/mol)}}$

Q: Which of the following is the correct conversion factor to go from molecules to moles?

$\frac{1 \text{ mole}}{6.022 \times 10^{23} \text{ molecules}}$

Question 1

Which of the following compounds would NOT be associated with the term 'formula unit'?

Accepted Answer

Br2

Question 2

Avogadro's number is defined as the number of particles in one mole of a substance. What is its value?

Accepted Answer

$6.022 	imes 10^{23}$

Question 3

How many moles of chlorine gas are there in $8.33 	imes 10^{23}$ molecules?

Accepted Answer

$1.38$ mol

Question 4

What is the mass of chlorine gas in 2.34 moles?

Accepted Answer

$165.91$ g

Question 5

How many grams of Cl$_2$ contain $9.25 	imes 10^{24}$ molecules of Cl$_2$?

Accepted Answer

$1.09 	imes 10^{3}$ g

Question 6

A sample of sodium chloride (NaCl) contains 73.1 kg. What is its number of formula units?

Accepted Answer

$7.55 	imes 10^{26}$

Question 7

Calculate the number of oxygen atoms found in 783.9 g of NaCl · 6 H$_2$O.

Accepted Answer

$1.57 	imes 10^{25}$

Question 8

If the density of water is $1.00$ g/mL at $25^{\circ}$C, calculate the number of water molecules found in $1.50 	imes 10^{3}$ \mu L of water.

Accepted Answer

$5.02 	imes 10^{22}$

Question 9

A cylindrical copper wire is used for fences around a house. The copper wire has a diameter of $0.0750$ in. How many copper atoms are found in a $5,160$ cm piece? (Density of copper is $8.96$ g/cm$^3$; $V = \pi r^2 h$)

Accepted Answer

$2.19 	imes 10^{24}$

Question 10

The density of the sun is $1.41$ g/cm$^3$ and its volume is $1.41 	imes 10^{27}$ m$^3$. How many hydrogen molecules are in the sun if we assume all the mass is hydrogen gas?

Accepted Answer

$7.44 	imes 10^{56}$

Question 11

Which of the following best describes a 'mole' in chemistry?

Accepted Answer

The mass of a substance containing the same number of units as atoms in 12.00 g of Carbon-12

Question 12

Which of the following is a correct formula for converting between mass and moles?

Accepted Answer

$	ext{moles} = \frac{	ext{mass (g)}}{	ext{molar mass (g/mol)}}$

Question 13

A molecule is defined as:

Accepted Answer

A compound with 2 or more nonmetals

Question 14

Which of the following is the correct sequence for converting from atoms to grams?

Accepted Answer

atoms $\rightarrow$ moles $\rightarrow$ grams

Question 15

If you have $3.00$ moles of H$_2$O, how many molecules of water do you have?

Accepted Answer

$1.81 	imes 10^{24}$

Question 16

Which of the following is NOT a correct statement about formula units?

Accepted Answer

Formula units are used for molecular compounds

Question 17

A sample contains $2.50$ moles of NaCl. How many formula units are present?

Accepted Answer

$1.51 	imes 10^{24}$

Question 18

Which of the following is the correct molar mass of Cl$_2$?

Accepted Answer

$70.90$ g/mol

Question 19

If a compound contains both metal and nonmetal elements, what is the general term for its smallest unit?

Accepted Answer

Formula unit

Question 20

Which of the following is the correct conversion factor to go from molecules to moles?

Accepted Answer

$\frac{1 	ext{ mole}}{6.022 	imes 10^{23} 	ext{ molecules}}$

The Mole: Conversions Between Mass, Moles, and Particles in GOB Chemistry

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