Magnesium reacts with hydrochloric acid to produce hydrogen gas. A series of experiments was carried out to measure the volume of gas produced under different conditions using a gas syringe.
The first experiment used 0.10g of magnesium ribbon reacting with 30cm3 of 0.50moldm–3 HCl solution. This reaction was carried out at 20°C. The results for this experiment are given in the following table.
a Sketch a diagram of the apparatus used for this experiment. Give the balanced equation for the reaction.
b Draw a graph of this data and use your graph to calculate the initial rate of reaction. Include the units for the rate of reaction.
c Interpret the shape of the graph and the variation in rate of reaction using the collision theory.
d Calculate the average rate of reaction over the first 150s.
e Why does the volume of gas collected not change after 150s?
f This experiment was repeated using 0.05g of magnesium ribbon. On the same axes used previously, sketch the graph that would be obtained. Label this graph B.
g The experiment was repeated under the same conditions but using 0.10g of powdered magnesium. On the same axes, sketch the graph that would be obtained. Label this graph C.
h The original experiment was repeated at 10°C. Again using the same axes, sketch the graph that would be obtained and label it graph D.
i Sketch the Maxwell–Boltzmann distribution for the first experiment and the experiment at 10°C. Use this to explain the effect of changing the temperature on the rate of this reaction.
The Correct Answer and Explanation is :
I’ll go step by step through each part of the question:
a) Sketch a diagram of the apparatus & Balanced Equation
The experiment uses:
- A conical flask containing magnesium and hydrochloric acid.
- A gas syringe to measure the volume of hydrogen gas produced.
- A delivery tube connecting the flask to the syringe.
Balanced Chemical Equation:
[
\text{Mg} (s) + 2\text{HCl} (aq) \rightarrow \text{MgCl}_2 (aq) + \text{H}_2 (g)
]
This equation shows that magnesium reacts with hydrochloric acid to produce magnesium chloride and hydrogen gas.
b) Graphing & Initial Rate Calculation
I’ll first plot the graph using the provided data and determine the initial rate of reaction.
Certainly! Let’s address each part of the question systematically:
a) Sketch a diagram of the apparatus used for this experiment. Provide the balanced equation for the reaction.
Apparatus Diagram:
he experiment involves reacting magnesium ribbon with hydrochloric acid in a conical flask. The hydrogen gas produced is collected using a gas syringe.
Balanced Chemical Equation:
[ \text{Mg (s)} + 2\text{HCl (aq)} \rightarrow \text{MgCl}_2\text{ (aq)} + \text{H}_2\text{ (g)} ]
b) Draw a graph of this data and use your graph to calculate the initial rate of reaction. Include the units for the rate of reaction.
o analyze the data, plot the volume of hydrogen gas produced (in cm³) on the y-axis against time (in seconds) on the x-axis.he initial rate of reaction can be determined by calculating the slope of the tangent to the curve at time zero.his slope represents the change in volume over the change in time (ΔV/Δt) at the start of the reaction.he units for the rate of reaction are cm³/s.
c) Interpret the shape of the graph and the variation in rate of reaction using collision theory.
he graph typically shows a steep slope at the beginning, indicating a fast reaction rate due to a high concentration of reactants.s the reaction progresses, the slope becomes less steep, reflecting a decrease in the reaction rate as the reactants are consumed.ccording to collision theory, the rate of reaction depends on the frequency and energy of collisions between reactant particles.nitially, with higher concentrations, there are more frequent collisions, leading to a higher reaction rate.s the reactants are depleted, collisions become less frequent, and the reaction rate decreases.
d) Calculate the average rate of reaction over the first 150 seconds.
he average rate of reaction over a specific time interval can be calculated by dividing the total volume of gas produced by the time taken.or the first 150 seconds, if the total volume of hydrogen gas produced is V cm³, then the average rate = V cm³ / 150 s.he units will be cm³/s.
e) Why does the volume of gas collected not change after 150 seconds?
he volume of gas collected plateaus after 150 seconds because the reaction has reached completion.t this point, one of the reactants (likely the magnesium) has been entirely consumed, and no more hydrogen gas is being produced.
f) This experiment was repeated using 0.05 g of magnesium ribbon. On the same axes used previously, sketch the graph that would be obtained. Label this graph B.
ith 0.05 g of magnesium, half the original mass, the total amount of hydrogen gas produced would be halved, assuming hydrochloric acid is in excess.he initial rate might be similar if the surface area and concentration conditions are unchanged, but the reaction would finish sooner, and the final volume of gas collected would be less.
g) The experiment was repeated under the same conditions but using 0.10 g of powdered magnesium. On the same axes, sketch the graph that would be obtained. Label this graph C.
owdered magnesium has a greater surface area compared to ribbon form, leading to more frequent collisions between reactant particles.his would result in a steeper initial slope, indicating a faster reaction rate.owever, the total volume of hydrogen gas produced would remain the same as in the original experiment, assuming the same mass of magnesium is used.
h) The original experiment was repeated at 10°C. Again using the same axes, sketch the graph that would be obtained and label it graph D.
owering the temperature to 10°C would decrease the kinetic energy of the reactant particles, resulting in fewer effective collisions per unit time.his would lead to a less steep initial slope, indicating a slower reaction rate.he total volume of hydrogen gas produced would remain the same, but it would take longer to reach completion.
i) Sketch the Maxwell–Boltzmann distribution for the first experiment and the experiment at 10°C. Use this to explain the effect of changing the temperature on the rate of this reaction.
he Maxwell–Boltzmann distribution illustrates the spread of kinetic energies among particles in a system.t a higher temperature (20°C), the distribution curve flattens and shifts to the right, indicating that more particles have higher kinetic energies.t a lower temperature (10°C), the curve is steeper and shifts to the left, showing that fewer particles have high kinetic energy.ince only particles with energy equal to or greater than the activation energy can successfully react, increasing the temperature results in a higher fraction of such particles, thereby increasing the reaction rate.onversely, decreasing the temperature reduces this fraction, leading to a slower reaction rate.
n summary, the rate of the reaction between magnesium and hydrochloric acid is influenced by factors such as reactant concentration, surface area, and temperature.nderstanding these effects through collision theory and the Maxwell–Boltzmann distribution provides insight into the kinetic behavior of chemical reactions.