End of chapter exercises | Quantitative aspects of chemical change

Write only the word/term for each of the following descriptions:

the mass of one mole of a substance
the number of particles in one mole of a substance

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$\text{5}$ $\text{g}$ of magnesium chloride is formed as the product of a chemical reaction. Select the true statement from the answers below:

$\text{0,08}$ moles of magnesium chloride are formed in the reaction
the number of atoms of $\text{Cl}$ in the product is $\text{0,6022} \times \text{10}^{\text{23}}$
the number of atoms of $\text{Mg}$ is $\text{0,05}$
the atomic ratio of $\text{Mg}$ atoms to $\text{Cl}$ atoms in the product is $1:1$

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2 moles of oxygen gas react with hydrogen. What is the mass of oxygen in the reactants?

$\text{32}$ $\text{g}$
$\text{0,125}$ $\text{g}$
$\text{64}$ $\text{g}$
$\text{0,063}$ $\text{g}$

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In the compound potassium sulphate ($\text{K}_{2}\text{SO}_{4}$), oxygen makes up $x\%$ of the mass of the compound. $x = ?$

$\text{36,8}$
$\text{9,2}$
4
$\text{18,3}$

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The concentration of a $\text{150}$ $\text{cm$^{3}$}$ solution, containing $\text{5}$ $\text{g}$ of $\text{NaCl}$ is:

$\text{0,09}$ $\text{mol·dm$^{-3}$}$
$\text{5,7} \times \text{10}^{-\text{4}}$ $\text{mol·dm$^{-3}$}$
$\text{0,57}$ $\text{mol·dm$^{-3}$}$
$\text{0,03}$ $\text{mol·dm$^{-3}$}$

Solution not yet available

Calculate the number of moles in:

$\text{5}$ $\text{g}$ of methane ($\text{CH}_{4}$)
$\text{3,4}$ $\text{g}$ of hydrochloric acid
$\text{6,2}$ $\text{g}$ of potassium permanganate ($\text{KMnO}_{4}$)
$\text{4}$ $\text{g}$ of neon
$\text{9,6}$ $\text{kg}$ of titanium tetrachloride ($\text{TiCl}_{4}$)

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Calculate the mass of:

$\text{0,2}$ $\text{mol}$ of potassium hydroxide ($\text{KOH}$)
$\text{0,47}$ $\text{mol}$ of nitrogen dioxide
$\text{5,2}$ $\text{mol}$ of helium
$\text{0,05}$ $\text{mol}$ of copper (II) chloride ($\text{CuCl}_{2}$)
$\text{31,31} \times \text{10}^{\text{23}}$ molecules of carbon monoxide (CO)

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Calculate the percentage that each element contributes to the overall mass of:

Chloro-benzene ($\text{C}_{6}\text{H}_{5}\text{Cl}$)
Lithium hydroxide ($\text{LiOH}$)

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CFC's (chlorofluorocarbons) are one of the gases that contribute to the depletion of the ozone layer. A chemist analysed a CFC and found that it contained $\text{58,64}\%$ chlorine, $\text{31,43}\%$ fluorine and $\text{9,93}\%$ carbon. What is the empirical formula?

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$\text{14}$ $\text{g}$ of nitrogen combines with oxygen to form $\text{46}$ $\text{g}$ of a nitrogen oxide. Use this information to work out the formula of the oxide.

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Iodine can exist as one of three oxides ($\text{I}_{2}\text{O}_{4}$; $\text{I}_{2}\text{O}_{5}$; $\text{I}_{4}\text{O}_{9}$). A chemist has produced one of these oxides and wishes to know which one they have. If he started with $\text{508}$ $\text{g}$ of iodine and formed $\text{652}$ $\text{g}$ of the oxide, which oxide has he produced?

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A fluorinated hydrocarbon (a hydrocarbon is a chemical compound containing hydrogen and carbon) was analysed and found to contain $\text{8,57}\%$ $\text{H}$, $\text{51,05}\%$ $\text{C}$ and $\text{40,38}\%$ $\text{F}$.

What is its empirical formula?
What is the molecular formula if the molar mass is $\text{94,1}$ $\text{g·mol$^{-1}$}$?

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Copper sulphate crystals often include water. A chemist is trying to determine the number of moles of water in the copper sulphate crystals. She weighs out $\text{3}$ $\text{g}$ of copper sulphate and heats this. After heating, she finds that the mass is $\text{1,9}$ $\text{g}$. What is the number of moles of water in the crystals? (Copper sulphate is represented by $\text{CuSO}_{4}.\text{xH}_{2}\text{O}$).

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$\text{300}$ $\text{cm$^{3}$}$ of a $\text{0,1}$ $\text{mol·dm$^{-3}$}$ solution of sulphuric acid is added to $\text{200}$ $\text{cm$^{3}$}$ of a $\text{0,5}$ $\text{mol·dm$^{-3}$}$ solution of sodium hydroxide.

Write down a balanced equation for the reaction which takes place when these two solutions are mixed.
Calculate the number of moles of sulphuric acid which were added to the sodium hydroxide solution.
Is the number of moles of sulphuric acid enough to fully neutralise the sodium hydroxide solution? Support your answer by showing all relevant calculations.

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A learner is asked to make $\text{200}$ $\text{cm$^{3}$}$ of sodium hydroxide ($\text{NaOH}$) solution of concentration $\text{0,5}$ $\text{mol·dm$^{-3}$}$.

Determine the mass of sodium hydroxide pellets he needs to use to do this.
Using an accurate balance the learner accurately measures the correct mass of the NaOH pellets. To the pellets he now adds exactly $\text{200}$ $\text{cm$^{3}$}$ of pure water. Will his solution have the correct concentration? Explain your answer.
The learner then takes $\text{300}$ $\text{cm$^{3}$}$ of a $\text{0,1}$ $\text{mol·dm$^{-3}$}$ solution of sulphuric acid ($\text{H}_{2}\text{SO}_{4}$) and adds it to $\text{200}$ $\text{cm$^{3}$}$ of a $\text{0,5}$ $\text{mol·dm$^{-3}$}$ solution of $\text{NaOH}$ at $\text{25}$ $\text{℃}$.
Write down a balanced equation for the reaction which takes place when these two solutions are mixed.
Calculate the number of moles of $\text{H}_{2}\text{SO}_{4}$ which were added to the $\text{NaOH}$ solution.

Solution not yet available

$\text{96,2}$ $\text{g}$ sulphur reacts with an unknown quantity of zinc according to the following equation: $\text{Zn} + \text{S} \rightarrow \text{ZnS}$

What mass of zinc will you need for the reaction, if all the sulphur is to be used up?
Calculate the theoretical yield for this reaction.
It is found that $\text{275}$ $\text{g}$ of zinc sulphide was produced. Calculate the % yield.

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Calcium chloride reacts with carbonic acid to produce calcium carbonate and hydrochloric acid according to the following equation:

\[\text{CaCl}_{2} + \text{H}_{2}\text{CO}_{3} \rightarrow \text{CaCO}_{3} + \text{HCl}\]

If you want to produce $\text{10}$ $\text{g}$ of calcium carbonate through this chemical reaction, what quantity (in g) of calcium chloride will you need at the start of the reaction?

Solution not yet available