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CHEMISTRY, M3 EQ-Bank 18

A student heats sodium metal, copper carbonate and propane gas \(\ce{(C3H8)}\) individually with a Bunsen burner. All of the substances react but only two of the substances react with the oxygen in the air.

Write a balanced chemical equation for each of the reactions that occurred.   (3 marks)

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Combustion of sodium metal:  \(\ce{2Na(s) + O2(g) -> 2NaO(s)}\)

Combustion of propane gas:  \(\ce{C3H8(g) + 5O2(g) -> 3CO2(g) + 4H2O(l)}\)

Decomposition of copper carbonate:  \(\ce{CuCO3(s) -> CuO(s) + CO2(g)}\)

Show Worked Solution

Combustion of sodium metal:  \(\ce{2Na(s) + O2(g) -> 2NaO(s)}\)

Combustion of propane gas:  \(\ce{C3H8(g) + 5O2(g) -> 3CO2(g) + 4H2O(l)}\)

Decomposition of copper carbonate:  \(\ce{CuCO3(s) -> CuO(s) + CO2(g)}\)

→ The last reaction is endothermic and so requires the heat of the Bunsen burner to proceed where as the first two require the heat of the Bunsen burner to overcome their activation energies.

CHEMISTRY, M3 EQ-Bank 5 MC

Which fuel produces the highest number of moles of carbon dioxide for every mole of oxygen consumed during complete combustion?

  1. Ethane, \(\ce{C2H6}\)
  2. Ethene, \(\ce{C2H4}\)
  3. Methane, \(\ce{CH4}\)
  4. Butane, \(\ce{C4H10}\)
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\(B\)

Show Worked Solution

Ethane: \(\ce{2C2H6 + 7O2 -> 4CO2 + 6H2O}\),   \(\ce{\frac{4}{7}CO2}\) per mole of \(\ce{O2}\)

Ethene: \(\ce{C2H4 + 3O2 -> 2CO2 + 2H2O}\),   \(\ce{\frac{2}{3}CO2}\) per mole of \(\ce{O2}\)

Methane: \(\ce{CH4 + 2O2 -> CO2 + 2H2O}\),   \(\ce{\frac{1}{2}CO2}\) per mole of \(\ce{O2}\)

Butane: \(\ce{2C4H10 + 13O2 -> 8CO2 + 10H2O}\),   \(\ce{\frac{8}{13}CO2}\) per mole of \(\ce{O2}\)

→ Ethene has the highest amount of \(\ce{CO2}\) per mole of \(\ce{O2}\) used up in the reaction.

\(\Rightarrow B\)

 

CHEMISTRY, M3 EQ-Bank 3 MC

Which of the following are the products of the complete combustion of propane, \(\ce{C3H8}\)?

  1. Carbon monoxide, soot and water
  2. Carbon dioxide, carbon monoxide, soot and water
  3. Carbon monoxide and water
  4. Carbon dioxide and water
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\(D\)

Show Worked Solution

→ A reaction which under goes complete combustion will produce carbon dioxide and water.

→ Carbon monoxide is a product of incomplete combustion which occurs when there is a lack of oxygen available.

\(\Rightarrow D\)

CHEMISTRY, M3 EQ-Bank 15

Write balanced chemical equations for each of the following reactions (states of matter are not required).

  1. The reaction between zinc and sulfuric acid.   (1 mark)

  2. The decomposition of calcium carbonate.   (1 mark)

  3. The incomplete combustion of ethane \(\ce{(C2H6)}\) with a limited amount of oxygen.   (1 mark)

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a.    \(\ce{Zn + H2SO4 -> ZnSO4 + H2}\)

b.    \(\ce{CaCO3 -> CaO + CO2}\)

c.    \(\ce{2C2H6 + 5O2 -> 4CO + 6H2O}\)

Show Worked Solution

a.    Active metal and acid

\[\ce{Zn + H2SO4 -> ZnSO4 + H2}\]

b.    Decomposition

\[\ce{CaCO3 -> CaO + CO2}\]

c.    Combustion

\[\ce{2C2H6 + 5O2 -> 4CO + 6H2O}\]

CHEMISTRY, M3 EQ-Bank 13

Write balanced chemical equations for each of the following reactions (states of matter are not required).

  1. The reaction between magnesium and hydrochloric acid.   (1 mark)

  2. The decomposition of ammonia.   (1 mark)

  3. The incomplete combustion of butane (\(\ce{C4H10}\)) with a limited amount of oxygen.   (1 mark)

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a.    \(\ce{Mg + 2HCl -> MgCl2 + H2}\)

b.    \(\ce{2NH3 -> N2 + 3H2}\)

c.    \(\ce{2C4H10 + 9O2 -> 8CO + 10H2O}\)

Show Worked Solution

a.   Reaction between active metal and acid

\(\ce{Mg + 2HCl -> MgCl2 + H2}\)

b.   Decomposition

\(\ce{2NH3 -> N2 + 3H2}\)

c.   Combustion

\(\ce{2C4H10 + 9O2 -> 8CO + 10H2O}\)

CHEMISTRY, M3 EQ-Bank 10

A chemical reaction takes place in a sealed vessel containing limewater.

As the reaction progresses the limewater turns from a clear colourless solution, to a milky white one.

Explain, using chemical equations or otherwise, how the reaction taking place could be either a decomposition or a combustion reaction.   (3 marks)

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→ Limewater turns milky in the presence of \(\ce{CO2}\).

→ The reaction in the above example could be either a decomposition or combustion reaction because both of these reactions can involve \(\ce{CO2}\) as a product.

→ Possible chemical equations include

Decomposition: \(\ce{CaCO3(s) \rightarrow CaO(s) + CO2(g)}\)

Combustion: \(\ce{CH4(aq) + 2O2(g) \rightarrow 2H2O(l) + CO2(g)}\)

Show Worked Solution

→ Limewater turns milky in the presence of \(\ce{CO2}\).

→ The reaction in the above example could be either a decomposition or combustion reaction because both of these reactions can involve \(\ce{CO2}\) as a product.

→ Possible chemical equations include

Decomposition: \(\ce{CaCO3(s) \rightarrow CaO(s) + CO2(g)}\)

Combustion: \(\ce{CH4(aq) + 2O2(g) \rightarrow 2H2O(l) + CO2(g)}\)

CHEMISTRY, M3 EQ-Bank 9

Two moles of butane \(\ce{C3H8(g)}\) were reacted with 224 grams of oxygen \(\ce{O2(g)}\).

  1. Write the balanced equation for this reaction.   (3 marks)

  2. Determine the mass, in grams, of \(\ce{CO2(g)}\) produced by this reaction.   (1 mark)

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i.    \(\ce{2C3H8(g) + 7O2(g)\ \rightarrow 2C(s) + 2CO(g) + 2CO2(g) + 8H2O(l)}\)

ii.    \(\ce{m(CO2) = 88.02\ \text{g}}\)

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i.    Complete combustion equation:

   \(\ce{C3H8(g) + 5O2(g)\ \rightarrow 3CO2(g) + 4H2O(l)} \)

→ Two moles of butane require 10 moles of oxygen to fully combust. 

→ \(\ce{n(O2) = \dfrac {m}{MM}= \dfrac {224}{32} = 7}\)

→ Oxygen is limiting reagent and butane will undergo incomplete combustion according to the following balanced equation:

   \(\ce{2C3H8(g) + 7O2(g)\ \rightarrow 2C(s) + 2CO(g) + 2CO2(g) + 8H2O(l)}\)

 

ii.    Using the equation in part (i), 2 moles of \(\ce{CO2}\) will be produced

\(\ce{m(CO2) = n \times MM = 2 \times 44.01 = 88.02\ \text{g}}\)

CHEMISTRY, M3 EQ-Bank 8

Many acid/metal reactions produce hydrogen gas. How can the presence of hydrogen gas be detected, and what type of reaction does this detection method utilise?   (2 marks)

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→ To test for the presence of hydrogen gas, collect the gas from the reaction and expose it to a naked flame. Hydrogen is highly flammable and if present, will produce a distinctive “pop” sound when it ignites.

→ This type of test is known as a combustion reaction.

Show Worked Solution

→ To test for the presence of hydrogen gas, collect the gas from the reaction and expose it to a naked flame. Hydrogen is highly flammable and if present, will produce a distinctive “pop” sound when it ignites.

→ This type of test is known as a combustion reaction.

CHEMISTRY, M3 EQ-Bank 5

Write a balanced chemical equation for the complete combustion of butane \(\ce{(C4H10)}\).   (2 marks)

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\(\ce{2C4H10(aq) + 13O2(g) \rightarrow 8CO2(g) + 10H2O(l)}\)

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→ Products of complete combustion are: \(\ce{CO2,\ H2O}\)

→ Balanced equation:

\(\ce{2C4H10(aq) + 13O2(g) \rightarrow 8CO2(g) + 10H2O(l)}\)

CHEMISTRY, M3 EQ-Bank 1

Complete the table below by outlining one physical indication of each chemical change described below.   (3 marks)

\begin{array} {|l|c|}
\hline
\rule{0pt}{2.5ex} \textit{Chemical Reaction} \rule[-1ex]{0pt}{0pt} & \ \ \ \ \ \ \ \ \ \ \ \ \ \ \textit{Physical Indication}\ \ \ \ \ \ \ \  \ \ \ \ \ \ \\
\hline
\rule{0pt}{2.5ex} \text{Precipitation} \rule[-1ex]{0pt}{0pt} &  \\
\hline
\rule{0pt}{2.5ex} \text{Combustion} \rule[-1ex]{0pt}{0pt} &  \\
\hline
\rule{0pt}{2.5ex} \text{Fermentation} \rule[-1ex]{0pt}{0pt} &  \\
\hline
\end{array}

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\begin{array} {|l|l|}
\hline
\rule{0pt}{2.5ex} \textit{Chemical Reaction} \rule[-1ex]{0pt}{0pt} & \ \ \ \ \ \ \ \ \ \ \textit{Physical Indication} \\
\hline
\rule{0pt}{2.5ex} \text{Precipitation} \rule[-1ex]{0pt}{0pt} & \text{Solid forms and falls out of solution} \\
\hline
\rule{0pt}{2.5ex} \text{Combustion} \rule[-1ex]{0pt}{0pt} & \text{Generation of heat and light} \\
\hline
\rule{0pt}{2.5ex} \text{Fermentation} \rule[-1ex]{0pt}{0pt} &  \text{Formation of gas (bubbles)} \\
\hline
\end{array}

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\begin{array} {|l|l|}
\hline
\rule{0pt}{2.5ex} \textit{Chemical Reaction} \rule[-1ex]{0pt}{0pt} & \ \ \ \ \ \ \ \ \ \ \textit{Physical Indication} \\
\hline
\rule{0pt}{2.5ex} \text{Precipitation} \rule[-1ex]{0pt}{0pt} & \text{Solid forms and falls out of solution} \\
\hline
\rule{0pt}{2.5ex} \text{Combustion} \rule[-1ex]{0pt}{0pt} & \text{Generation of heat and light} \\
\hline
\rule{0pt}{2.5ex} \text{Fermentation} \rule[-1ex]{0pt}{0pt} &  \text{Formation of gas (bubbles)} \\
\hline
\end{array}