Question

Part A (14 marks) - Rate of reaction Students completed an experiment to determine the effect of concentration on the rate of reaction. In the experiment they added hydrochloric acid to a solutions of sodium thiosulphate with varying concentration at \( 298 \mathrm{~K} \), resulting in the formation of colloidal sulphur which precipitates and causes the reaction to become cloudy. \[ \mathrm{Na}_{2} \mathrm{~S}_{2} \mathrm{O}_{3}(\mathrm{aq})+\mathrm{HCl}(\mathrm{aq}) \rightarrow 2 \mathrm{NaCl}(\mathrm{aq})+\mathrm{S}(\mathrm{s})+\mathrm{SO}_{2}(\mathrm{~g})+\mathrm{H}_{2} \mathrm{O}(\mathrm{I}) \] Students recorded time required for a black cross placed under the reaction beaker to become invisible due to the build up of colloidal sulphur (blackout time). Results \begin{tabular}{|l|l|l|l|} \hline Run & \begin{tabular}{l} {\( \left[\mathrm{S}_{2} \mathrm{O}_{3}{ }^{2-}\right] \) in reaction } \\ mixture (M) \end{tabular} & Blackout time (s) & 1 blackout time \( \left(\mathrm{s}^{-1}\right) \) \\ \hline 1 & 0.22 & 19.8 & \( 0.05 \mathrm{~s}^{-1} \) \\ \hline 2 & 0.19 & 21.3 & \( 0.05 \mathrm{~s}^{-1} \) \\ \hline 3 & 0.17 & 24.1 & \( 0.04 \mathrm{~s}^{-1} \) \\ \hline 4 & 0.14 & 29.9 & \( 0.03 \mathrm{~s}^{-1} \) \\ \hline 5 & 0.12 & 37.5 & \( 0.03 \mathrm{~s}^{-1} \) \\ \hline 6 & 0.09 & 48.7 & \( 0.02 \mathrm{~s}^{-1} \) \\ \hline \end{tabular} Question 1. (1 mark) Complete the table by calculating the rate of reaction (1/blackout time). Question 2. (3 marks) Identify the following variables in this experiment. Independent variable The concentrations of sodinus triosndehase Dependent variable The qusount of blackont time. Control variable The amoment of hydrochloric asid adoled

          Part A (14 marks) - Rate of reaction
Students completed an experiment to determine the effect of concentration on the rate of reaction. In the experiment they added hydrochloric acid to a solutions of sodium thiosulphate with varying concentration at \( 298 \mathrm{~K} \), resulting in the formation of colloidal sulphur which precipitates and causes the reaction to become cloudy.
\[
\mathrm{Na}_{2} \mathrm{~S}_{2} \mathrm{O}_{3}(\mathrm{aq})+\mathrm{HCl}(\mathrm{aq}) \rightarrow 2 \mathrm{NaCl}(\mathrm{aq})+\mathrm{S}(\mathrm{s})+\mathrm{SO}_{2}(\mathrm{~g})+\mathrm{H}_{2} \mathrm{O}(\mathrm{I})
\]

Students recorded time required for a black cross placed under the reaction beaker to become invisible due to the build up of colloidal sulphur (blackout time).

Results
\begin{tabular}{|l|l|l|l|}
\hline Run & \begin{tabular}{l}
{\( \left[\mathrm{S}_{2} \mathrm{O}_{3}{ }^{2-}\right] \) in reaction } \\
mixture (M)
\end{tabular} & Blackout time (s) & 1 blackout time \( \left(\mathrm{s}^{-1}\right) \) \\
\hline 1 & 0.22 & 19.8 & \( 0.05 \mathrm{~s}^{-1} \) \\
\hline 2 & 0.19 & 21.3 & \( 0.05 \mathrm{~s}^{-1} \) \\
\hline 3 & 0.17 & 24.1 & \( 0.04 \mathrm{~s}^{-1} \) \\
\hline 4 & 0.14 & 29.9 & \( 0.03 \mathrm{~s}^{-1} \) \\
\hline 5 & 0.12 & 37.5 & \( 0.03 \mathrm{~s}^{-1} \) \\
\hline 6 & 0.09 & 48.7 & \( 0.02 \mathrm{~s}^{-1} \) \\
\hline
\end{tabular}

Question 1. (1 mark)
Complete the table by calculating the rate of reaction (1/blackout time).

Question 2. (3 marks)
Identify the following variables in this experiment.
Independent variable
The concentrations of sodinus triosndehase
Dependent variable
The qusount of blackont time.
Control variable
The amoment of hydrochloric asid adoled

Part A (14 marks) - Rate of reaction
Students completed an experiment to determine the effect of concentration on the rate of reaction. In the experiment they added hydrochloric acid to a solutions of sodium thiosulphate with varying concentration at 298 K, resulting in the formation of colloidal sulphur which precipitates and causes the reaction to become cloudy.

Na2 S2O3(aq)+HCl(aq) → 2 NaCl(aq)+S(s)+SO2( g)+H2O(I)

Students recorded time required for a black cross placed under the reaction beaker to become invisible due to the build up of colloidal sulphur (blackout time).

Results

Run
[S2O3^2-] in reaction

mixture (M)
Blackout time (s) 1 blackout time (s^-1)

1 0.22 19.8 0.05 s^-1

2 0.19 21.3 0.05 s^-1

3 0.17 24.1 0.04 s^-1

4 0.14 29.9 0.03 s^-1

5 0.12 37.5 0.03 s^-1

6 0.09 48.7 0.02 s^-1

Question 1. (1 mark)
Complete the table by calculating the rate of reaction (1/blackout time).

Question 2. (3 marks)
Identify the following variables in this experiment.
Independent variable
The concentrations of sodinus triosndehase
Dependent variable
The qusount of blackont time.
Control variable
The amoment of hydrochloric asid adoled

Added by Nicole H.

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