Electrolysis and photolysis are examples of which type of reaction?
- Combustion
- Acid/Base
- Synthesis
- Decomposition
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Electrolysis and photolysis are examples of which type of reaction?
\(D\)
→ Both electrolysis and photolysis involve the breakdown of compounds into simpler substances under decomposition reactions.
\(\Rightarrow D\)
Two moles of butane \(\ce{C3H8(g)}\) were reacted with 224 grams of oxygen \(\ce{O2(g)}\).
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i. \(\ce{2C3H8(g) + 7O2(g)\ \rightarrow 2C(s) + 2CO(g) + 2CO2(g) + 8H2O(l)}\)
ii. \(\ce{m(CO2) = 88.02\ \text{g}}\)
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
\(\ce{m(CO2) = n \times MM = 2 \times 44.01 = 88.02\ \text{g}}\)
Sodium and zinc are each reacted with water and steam. Predict the observations that would be made about these reactions. (4 marks)
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Sodium \((\ce{Na}) \):
→ Sodium is an alkali metal that will react vigorously with both water and steam to produce a hydroxide and hydrogen gas according to the chemical equation
\(\ce{2Na(s) + 2H2O(l) \rightarrow 2NaOH(aq) + H2(g)} \)
→ The reaction will show no colour change in the aqueous solution as \(\ce{Na(aq)}\) is colourless like water.
Zinc \((\ce{Zn})\):
→ Zinc is less reactive and will not react with water but will form an oxide with steam (due to the higher energy present) according to the equation
\(\ce{Zn(s) + H2O(steam) \rightarrow ZnO(aq) + H2(g)} \)
→ While zinc metal is a silver colour, zinc oxide is white.
Sodium \((\ce{Na}) \):
→ Sodium is an alkali metal that will react vigorously with both water and steam to produce a hydroxide and hydrogen gas according to the chemical equation
\(\ce{2Na(s) + 2H2O(l) \rightarrow 2NaOH(aq) + H2(g)} \)
→ The reaction will show no colour change in the aqueous solution as \(\ce{Na(aq)}\) is colourless like water.
Zinc \((\ce{Zn})\):
→ Zinc is less reactive and will not react with water but will form an oxide with steam (due to the higher energy present) according to the equation
\(\ce{Zn(s) + H2O(steam) \rightarrow ZnO(aq) + H2(g)} \)
→ While zinc metal is a silver colour, zinc oxide is white.
Three unknown metals are reacted with dilute \(\ce{HCl(aq)}\) and the following observations are made:
\begin{array} {|c|l|}
\hline
\rule{0pt}{2.5ex} \textit{Metal} \rule[-1ex]{0pt}{0pt} & \ \ \ \ \ \ \textit{Observations} \\
\hline
\rule{0pt}{2.5ex} \text{A} \rule[-1ex]{0pt}{0pt} & \text{No observable reaction} \\
\hline
\rule{0pt}{2.5ex} \text{B} \rule[-1ex]{0pt}{0pt} & \text{Slow bubbling} \\
\hline
\rule{0pt}{2.5ex} \text{C} \rule[-1ex]{0pt}{0pt} & \text{Fast, abrupt bubbling} \\
\hline
\end{array}
You are told that the metals in question are Magnesium, Platinum and Zinc.
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i. → The metals \(\text{A}\), \(\text{B}\) and \(\text{C}\) differ by their relative reactivity.
→ Magnesium is the most reactive as it is an alkali earth metal (Metal \(\text{C}\)).
→ Zinc and Platinum are both less reactive than magnesium. Zinc however exists higher on the reactivity series of metals than Platinum which is the least reactive of the three metals.
→ Therefore, metal \(\text{B}\) is zinc and metal \(\text{A}\) is platinum.
ii. → A single displacement reaction.
iii. Include one of the following:
\(\ce{Mg(s) + 2HCl(aq) \rightarrow MgCl2(aq) + H2(g) }\)
\(\ce{Zn(s) + 2HCl(aq) \rightarrow ZnCl2(aq) + H2(g) }\)
i. → The metals \(\text{A}\), \(\text{B}\) and \(\text{C}\) differ by their relative reactivity.
→ Magnesium is the most reactive as it is an alkali earth metal (Metal \(\text{C}\)).
→ Zinc and Platinum are both less reactive than magnesium. Zinc however exists higher on the reactivity series of metals than Platinum which is the least reactive of the three metals.
→ Therefore, metal \(\text{B}\) is zinc and metal \(\text{A}\) is platinum.
ii. → A single displacement reaction.
iii. Include one of the following:
\(\ce{Mg(s) + 2HCl(aq) \rightarrow MgCl2(aq) + H2(g) }\)
\(\ce{Zn(s) + 2HCl(aq) \rightarrow ZnCl2(aq) + H2(g) }\)