Experiment for testing type of catalyst on reaction rate?

[Marie Cailey]

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experiment for testing type of catalyst on reaction rate?

I need an experiment (just the method) Where I can test the reaction rate of changing the catalyst type

I need about 3 differnet catalysts e.g. manganese oxide

it's the rate of decomposition of hydrogen peroxide

Thanks
!

 

[Ygggdrasil]

In general, what you'd want to do is to measure the concentration of reactant or product at different timepoints during the reaction to measure the rate of reactant disapearance or product generation. So, for the decomposition of hydrogen peroxide, you could either look at the rate at which the catalyst uses up hydrogen peroxide or the rate at which the catalyst generates oxygen gas.

For measuring hydrogen peroxide concentrations, there are some colorimetric assay you can use to measure its concentration (google h2o2 colorimetric assay). For measuring oxygen concentrations, here's a relatively simple, and fun method I found: http://www.nature.com/articles/srep03081

 

[Marie Cailey]

In general, what you'd want to do is to measure the concentration of reactant or product at different timepoints during the reaction to measure the rate of reactant disapearance or product generation. So, for the decomposition of hydrogen peroxide, you could either look at the rate at which the catalyst uses up hydrogen peroxide or the rate at which the catalyst generates oxygen gas.

For measuring hydrogen peroxide concentrations, there are some colorimetric assay you can use to measure its concentration (google h2o2 colorimetric assay). For measuring oxygen concentrations, here's a relatively simple, and fun method I found: http://www.nature.com/articles/srep03081

Thank you. I am going to use the rate at which Oxygen is produced using a gas syringe. Shall I measure the product of Oxygen every 5 seconds or not because there will be three different types of catalysts I'm going to use?

Also I need a hypothesis. Will this just be "The rate of reaction is affected by different types of catalysts" or not? I'm not entirely sure myself about this hypothesis

 

[Ygggdrasil]

Thank you. I am going to use the rate at which Oxygen is produced using a gas syringe. Shall I measure the product of Oxygen every 5 seconds or not because there will be three different types of catalysts I'm going to use?

How frequently you measure depends on the overall rate of reaction. If the oxygen is generated very quickly, you'd likely need to sample very frequently. You could start with that rate (if it's feasible), look at the preliminary results and see whether you need to adjust.

Also I need a hypothesis. Will this just be "The rate of reaction is affected by different types of catalysts" or not? I'm not entirely sure myself about this hypothesis

Sure, that's a reasonable hypothesis. Just be sure to devise your experiment and analysis to be able to address that hypothesis and its alternatives (for example, thinking about what sorts of statistics you'd need to accept/reject such a hypothesis).

 

[Marie Cailey]

How frequently you measure depends on the overall rate of reaction. If the oxygen is generated very quickly, you'd likely need to sample very frequently. You could start with that rate (if it's feasible), look at the preliminary results and see whether you need to adjust.
Sure, that's a reasonable hypothesis. Just be sure to devise your experiment and analysis to be able to address that hypothesis and its alternatives (for example, thinking about what sorts of statistics you'd need to accept/reject such a hypothesis).

I was thinking maybe instead of measuring every 5 seconds, I could time how long it takes for 25ml of gas to be produced. Would this be a good idea? Because I could then work out the reaction rate by diving the 25 by the time taken in seconds using a stopwatch. Do you have any better idea that could get me more marks?

 

[Ygggdrasil]

Measuring every 5 s would probably be best, especially if you want to run a negative control (no catalyst).

 

[PWiz]

Because I could then work out the reaction rate by diving the 25 by the time taken in seconds using a stopwatch.

This would give you the average rate of reaction over a (relatively long) period of time. It is unlikely to give precise results. An alternate method is to measure and compare the initial rate of reaction using different catalysts by finding the time taken to liberate a much smaller volume of oxygen, and then using this to find the average rates and compare.

 

[Marie Cailey]

Measuring every 5 s would probably be best, especially if you want to run a negative control (no catalyst).

I'm not doing the experiment without a catalyst, though. I am just testing three catalysts to find the rate of reaction and which works the best. But

This would give you the average rate of reaction over a (relatively long) period of time. It is unlikely to give precise results. An alternate method is to measure and compare the initial rate of reaction using different catalysts by finding the time taken to liberate a much smaller volume of oxygen, and then using this to find the average rates and compare.

So you mean basically measure how long it takes to get to 10ml or even less and then comparing?

 

[PWiz]

So you mean basically measure how long it takes to get to 10ml or even less and then comparing?

Yes, something along those lines. The volume selected should take around 5 seconds or less to be produced.

 

[Ygggdrasil]

I'm not doing the experiment without a catalyst, though. I am just testing three catalysts to find the rate of reaction and which works the best. But

You should always try to do some form of negative control. For example, what if you didn't clean your glassware thoroughly and some catalyst from previous experiments contaminated one of your reagents?

 

[Marie Cailey]

You should always try to do some form of negative control. For example, what if you didn't clean your glassware thoroughly and some catalyst from previous experiments contaminated one of your reagents?

What do you mean by Negative Control? Also, what do you mean by a preliminary experiment. One before hand? But what's the purpose for that. And what catalysts would you test for it?

 

[PWiz]

What do you mean by Negative Control?

It's a control experiment in which a result is not expected.

Also, what do you mean by a preliminary experiment. One before hand? But what's the purpose for that.

It's usually an experiment done in the starting with relatively low accuracy to get a rough idea of the kind of values you are expecting. For example, it is common practice in titration experiments to perform a "rough titre" first, where the acid in the burette is not run off so carefully. The idea behind it is to obtain a rough value around which neutralization occurs (indicator changes color), such as between 25-30 cm^3. This enables you to run off the acid quickly and bring it close to 20 cm^3 in the next experiment and then slow down and carefully determine the end point (allowing you to zoom in on the value faster).

 

[Ygggdrasil]

What do you mean by Negative Control?

A reaction where your experimental variable (catalyst) is not present. For example, if you experiment involved mixing 5 mL of a hydrogen peroxide solution with 1mL of your catalyst dissolved a diluent, in your negative control, you would add 1 mL of the diluent (without any catalyst in it) to the 5 mL of hydrogen peroxide solution. In the case of solid-phase catalysts like Mn, you could probably just omit that step for your negative control.

 

[Marie Cailey]

It's a control experiment in which a result is not expected.

It's usually an experiment done in the starting with relatively low accuracy to get a rough idea of the kind of values you are expecting. For example, it is common practice in titration experiments to perform a "rough titre" first, where the acid in the burette is not run off so carefully. The idea behind it is to obtain a rough value around which neutralization occurs (indicator changes color), such as between 25-30 cm^3. This enables you to run off the acid quickly and bring it close to 20 cm^3 in the next experiment and then slow down and carefully determine the end point (allowing you to zoom in on the value faster).

Hmm. Well in the case of my objective I don't think it is necessary for me to do one as instructed. Thanks, though; I'll remember for the future.

I am using these equipment, but I would like some things queried.

Rubber bung
Delivery Tube
Gas Syringe (do I need to state it's volume?)
Conical Flash (to contain the catalyst)
Manganese Oxide
Copper Oxide
Zinc Oxide
Spatula (to measure the catalyst) (How much would be suitable to use?)
Hydrogen Peroxide
Measuring Cylinder (to measure the hydrogen peroxide)
StopWatch
Goggles
Clamp Stand

 

[Marie Cailey]

Another query too: Should I say, for the equipment, "A selection of catalysts" or just three catalysts that I want to use(Manganese Oxide, zinc oxide, copper oxide) - wouldn't this make it more reproducible?

 

[Ygggdrasil]

Another query too: Should I say, for the equipment, "A selection of catalysts" or just three catalysts that I want to use(Manganese Oxide, zinc oxide, copper oxide) - wouldn't this make it more reproducible?

In the materials, section you should clearly state which catalysts you're testing.

When thinking about the amount of catalyst to add, it's worth thinking about how you will compare the efficiencies of the catalysts in order to test your hypothesis. Will the rate of reaction depend on the amount of catalyst added? Will it depend on the weight of catalyst added, the number of moles of catalyst, or some other factor?

 

[Marie Cailey]

In the materials, section you should clearly state which catalysts you're testing.

When thinking about the amount of catalyst to add, it's worth thinking about how you will compare the efficiencies of the catalysts in order to test your hypothesis. Will the rate of reaction depend on the amount of catalyst added? Will it depend on the weight of catalyst added, the number of moles of catalyst, or some other factor?

So I should list my three catalysts that I want to use?
Is it manganese oxide or manganese dioxide

I keep reading that they are the same but clearly not. Which should I use in an investigation? Manganese oxide?

 

[PWiz]

Is it manganese oxide or manganese dioxide

Actually it's manganese (IV) oxide. Manganese is a transition element (it has an incomplete d sub-shell) and has variable oxidation states. It is standard practice to give the oxidation state of the atom with variable ox. states in brackets while naming a particular compound (unless all the atoms in the compound have fixed ox. states).

 

[Marie Cailey]

Actually it's manganese (IV) oxide. Manganese is a transition element (it has an incomplete d sub-shell) and has variable oxidation states. It is standard practice to give the oxidation state of the atom with variable ox. states in brackets while naming a particular compound (unless all the atoms in the compound have fixed ox. states).

Thank you
ALso are they the correct equipment? I'm not sure if I should say the volume of the containers e.g. the measuring cylinder or conical flask?

 

[Marie Cailey]

Actually it's manganese (IV) oxide. Manganese is a transition element (it has an incomplete d sub-shell) and has variable oxidation states. It is standard practice to give the oxidation state of the atom with variable ox. states in brackets while naming a particular compound (unless all the atoms in the compound have fixed ox. states).

Also, what would the independent variables and dependent variables be in this investigation?

 

[PWiz]

Thank you
ALso are they the correct equipment? I'm not sure if I should say the volume of the containers e.g. the measuring cylinder or conical flask?

It always makes sense to state precisely the specifics about the apparatus used. As you've previously noted, this makes the experiment much more reproducible for anyone wishing to verify your results.

 

[PWiz]

Also, what would the independent variables and dependent variables be in this investigation?

Before I say anything, I'd like to first hear what you think about them.

 

[Marie Cailey]

It always makes sense to state precisely the specifics about the apparatus used. As you've previously noted, this makes the experiment much more reproducible for anyone wishing to verify your results.

So i SHOULD state on equipment "A selection of catalysts e.g. ...then the ones i just mentioned"?
This is my equipment so far
Gas syringe
Rubber bung
Delivery tube
3 x Different catalysts E.g. ...the 3 catalysts
Hydrogen Peroxide
Measuring Cylinder
Conical flask
stopwatch
Goggles
Clamp stand
Top pan balance

Does that list seem okay? Or do I need to to state the capacity of things like the measuring cylinder and conical flash

 

[Marie Cailey]

Before I say anything, I'd like to first hear what you think about them.

Independent variable - Type of catalyst
Dependent variable - Oxygen produced
Control Variable - Temperature at which the reaction occurs
Mass of the catalyst
Surface area of the catalyst

anythin else?

 

[Marie Cailey]

Also, do I need to include about the concentration of hydrogen peroxide? I can't just put hydrogen peroxide right?

 

[PWiz]

So i SHOULD state on equipment "A selection of catalysts e.g. ...then the ones i just mentioned"?

Yes.

Does that list seem okay?

I think so. It's hard to make a mental checklist of these sort of things though, so you might realize you need some other piece of equipment while you actually try to perform the experiment. I would recommend you visit a lab a few days before you perform the actual experiment and loosely set up the apparatus. You might spot something you'll need in the actual run.

do I need to to state the capacity of things like the measuring cylinder and conical flash

They are not actively used in the experiment, but it doesn't hurt to add that piece of information.

Mass of the catalyst

I would say the number of moles of the catalyst used would be a better choice.

Also, do I need to include about the concentration of hydrogen peroxide?

For standardization purposes, yes.

 

[berkeman]

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