EduNinjaPasteurization is used to eliminate pathogenic bacteria. The concentration of vitamin C was monitored over a period of time in pasteurized and unpasteurized orange juice.
Calculate the average rate of decrease of vitamin C concentration for pasteurized juice, in day , for the first 56 days.
Deduce, referring to the graph, whether pasteurization affects the rate of change of vitamin C concentration during storage of orange juice.
Pasteurization is used to eliminate pathogenic bacteria. The concentration of vitamin C was monitored over a period of time in pasteurized and unpasteurized orange juice.
Calculate the average rate of decrease of vitamin C concentration for pasteurized juice, in day , for the first 56 days.
Deduce, referring to the graph, whether pasteurization affects the rate of change of vitamin C concentration during storage of orange juice.
This question is about the rate of reaction between bromine and methanoic acid.
State and explain how the rate of this reaction, measured in , could be monitored experimentally.
The change in bromine concentration was monitored.
Determine the instantaneous rate of reaction to two significant figures when .
Outline why the graph has a negative non-linear slope.
Reason for negative slope:
Reason for non-linear slope:
Hydrogen peroxide decomposes to form water and oxygen.
The reaction is catalysed by solid manganese (IV) oxide, .
A student carried out a series of experiments to determine how the rate of decomposition depends on the mass of catalyst. Each time a different mass of was added to of hydrogen peroxide solution. The oxygen was collected in a graduated gas syringe and the volume recorded at regular intervals.
Figure 1
The student hypothesized, based on underlying theory, that doubling the mass of would double the rate of the catalysed reaction.
Explain how the student's hypothesis might be supported by collision theory.
The results from Figure 1 were processed to produce a graph showing how the initial rate varied with the mass of catalyst.
Figure 2
Outline how the y-axis values on Figure 2 were obtained from the results in Figure 1.
Hydrogen peroxide decomposes to form water and oxygen.
The reaction is catalysed by solid manganese (IV) oxide, .
A student carried out a series of experiments to determine how the rate of decomposition depends on the mass of catalyst. Each time a different mass of was added to of hydrogen peroxide solution. The oxygen was collected in a graduated gas syringe and the volume recorded at regular intervals.
Figure 1
The student hypothesized, based on underlying theory, that doubling the mass of would double the rate of the catalysed reaction.
Explain how the student's hypothesis might be supported by collision theory.
The results from Figure 1 were processed to produce a graph showing how the initial rate varied with the mass of catalyst.
Figure 2
Outline how the y-axis values on Figure 2 were obtained from the results in Figure 1.
Suggest, giving a reason, whether a best-fit line for Figure 2 should pass through the origin.
A student investigated the effect of concentration on the rate of reaction between sodium thiosulfate, , and hydrochloric acid, HCl .
Since the solid sulfur product is insoluble, the rate can be determined by measuring the time it takes for the clear solution to turn off-white or pale yellow until the X mark on a white tile below the flask can no longer be seen.
The student recorded the following data.
The solutions of sodium thiosulfate were in fact, all made as accurately as possible from the solid sodium thiosulfate by weighing the appropriate mass with a balance that can measure to one hundredth of a gram ( ), rather than by dilution of a stock solution.
Estimate the rate of the reaction for , giving the correct units.
Hydrogen peroxide, , releases oxygen gas, , as it decomposes according to the equation below.
of hydrogen peroxide solution was placed in a boiling tube, and a drop of liquid detergent was added to create a layer of bubbles on the top of the hydrogen peroxide solution as oxygen gas was released. The tube was placed in a water bath at and the height of the bubble layer was measured every thirty seconds. A graph was plotted of the height of the bubble layer against time.
Use the graph to calculate the rate of decomposition of hydrogen peroxide at 120 s .
Hydrogen peroxide, , releases oxygen gas, , as it decomposes according to the equation below.
of hydrogen peroxide solution was placed in a boiling tube, and a drop of liquid detergent was added to create a layer of bubbles on the top of the hydrogen peroxide solution as oxygen gas was released. The tube was placed in a water bath at and the height of the bubble layer was measured every thirty seconds. A graph was plotted of the height of the bubble layer against time.
Explain why the curve reaches a maximum.
Use the graph to calculate the rate of decomposition of hydrogen peroxide at 120 s .
Propanone reacts with bromine in acidic solution according to the following equation.
A student investigated the kinetics of this reaction using data logging equipment. Her data are shown below.
Calculate the rate of reaction for Experiment 5 and comment on the precision of your result.
Deduce the order of reaction with respect to and .
Deduce the rate expression for the reaction. Calculate the rate constant and state its units.
The student proposed the following mechanism for this reaction.
Comment on whether or not the order with respect to bromine supports this hypothesis.
Reaction kinetics can be investigated using the iodine clock reaction. The equations for two reactions that occur are given below.
Reaction B is much faster than reaction A , so the iodine, , formed in reaction A immediately reacts with thiosulfate ions, , in reaction B , before it can react with starch to form the familiar blue-black, starch-iodine complex.
In one experiment the reaction mixture contained:
of hydrogen peroxide of 1 % aqueous starch
of sulfuric acid of sodium thiosulfate of water with of potassium iodide (KI) dissolved in it.
After 45 seconds this mixture suddenly changed from colourless to blue-black.
The colour change occurs when of iodine has been formed. Use the total volume of the solution and the time taken, to calculate the rate of the reaction, including appropriate units.