Matter and Moles

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GED Science › Matter and Moles

Questions 1 - 6

How many molecules are in 3.72mol of fluorine?

$2.24\times10^{24}\ \text{molecules}$

$6.18\times10^{-24}\ \text{molecules}$

$70.68\ \text{molecules}$

$0.20\ \text{molecules}$

Explanation

Convert from moles to molecules using Avogadro's number:

$(\text{moles})\times(\frac{6.02\times10^{23}\text{molecules}}{\text{mole}})=\text{molecules}$

Use the moles given in the question to solve.

$3.72mol\times \frac{6.02\times10^{23}\ \text{molecules}}{1mol}=2.24\times10^{24}\ \text{molecules}$

How many molecules are in 3.72mol of fluorine?

$2.24\times10^{24}\ \text{molecules}$

$6.18\times10^{-24}\ \text{molecules}$

$70.68\ \text{molecules}$

$0.20\ \text{molecules}$

Explanation

Convert from moles to molecules using Avogadro's number:

$(\text{moles})\times(\frac{6.02\times10^{23}\text{molecules}}{\text{mole}})=\text{molecules}$

Use the moles given in the question to solve.

$3.72mol\times \frac{6.02\times10^{23}\ \text{molecules}}{1mol}=2.24\times10^{24}\ \text{molecules}$

Atomic mass values:

$H\rightarrow 1.0\frac{g}{mol}$

$S\rightarrow 32.1\frac{g}{mol}$

$O\rightarrow 16.0\frac{g}{mol}$

Convert the following mass to moles:

$12.05g\ H_2SO_4$

$0.12\ \text{moles}$

$1181.80\ \text{moles}$

$7.40\times 10^{24}\ \text{moles}$

$7.12\times 10^{26}\ \text{moles}$

Explanation

To convert grams to moles, use the molecular weight of the molecule. This is found by adding the mass of each atom.

$H_2SO_4\rightarrow 2(H)+1(S)+4(O)$

$2(1.0\frac{g}{mol})+(32.1\frac{g}{mol})+4(16.0\frac{g}{mol})=98.1\frac{g}{mol}$

$\frac{98.1g\ H_2SO_4}{1mol\ H_2SO_4}$

Now we can use the molecular mass to convert the given mass in the question to moles. Make sure to align the values so that the units cancel out.

$12.05g\ H_2SO_4\times \frac{1mol\ H_2SO_4}{98.1g\ H_2SO_4}=0.12mol\ H_2SO_4$

Atomic mass values:

$H\rightarrow 1.0\frac{g}{mol}$

$S\rightarrow 32.1\frac{g}{mol}$

$O\rightarrow 16.0\frac{g}{mol}$

Convert the following mass to moles:

$12.05g\ H_2SO_4$

$0.12\ \text{moles}$

$1181.80\ \text{moles}$

$7.40\times 10^{24}\ \text{moles}$

$7.12\times 10^{26}\ \text{moles}$

Explanation

To convert grams to moles, use the molecular weight of the molecule. This is found by adding the mass of each atom.

$H_2SO_4\rightarrow 2(H)+1(S)+4(O)$

$2(1.0\frac{g}{mol})+(32.1\frac{g}{mol})+4(16.0\frac{g}{mol})=98.1\frac{g}{mol}$

$\frac{98.1g\ H_2SO_4}{1mol\ H_2SO_4}$

Now we can use the molecular mass to convert the given mass in the question to moles. Make sure to align the values so that the units cancel out.

$12.05g\ H_2SO_4\times \frac{1mol\ H_2SO_4}{98.1g\ H_2SO_4}=0.12mol\ H_2SO_4$

Molecules are constantly moving. In which state of matter do molecules move the fastest?

Gases

Liquids

Solids

Molecules move at the same rate in both gases and liquids

Molecules move at the same rate in all three states of matter

Explanation

The movement of particles is important in differentiating the states of matter. Solids have the lowest molecular energy; their molecules barely vibrate and are generally trapped in lattice structures. Molecules in liquids are able to move more freely, resulting in the fluidity of the liquid state. Gas molecules have even more freedom of movement, allowing the gas to expand to fill a space.

Consider that energy (such as heat) must be added to convert a solid to a liquid or a liquid to a gas. That energy goes to make the molecules move faster and increase the temperature of the compound. Gases require the most energy (consider boiling water), and will have the fastest moving molecules.

Molecules are constantly moving. In which state of matter do molecules move the fastest?

Gases

Liquids

Solids

Molecules move at the same rate in both gases and liquids

Molecules move at the same rate in all three states of matter