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Lab Report Chemical Reaction Rate design lab

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I really want to do well in these labs, but my teacher is just crazy and I'm not a good chemist...n I study in Chem SL (forced to change to SL from HL:[ )

So I need to do a chemical reaction rate design lab...I am completely clueless.

I mean, I know what the factors could be, temperature and concentration etc.

I am really really stuck :[

Please help.

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I really want to do well in these labs, but my teacher is just crazy and I'm not a good chemist...n I study in Chem SL (forced to change to SL from HL:[ )

So I need to do a chemical reaction rate design lab...I am completely clueless.

I mean, I know what the factors could be, temperature and concentration etc.

I am really really stuck :[

Please help.

Hey,

There are two main ways of measuring the rate of a reaction. Volume of gas produced, or mass lost method.

In the volume produced the thing you have to make sure about the experiment is that the enviroment is airtight. Also you must have some way of collecting the gas and measuring it (either downward displacement of water with a measuring cylinder or simply use a gas cylinder).

Mass loss is simply putting your experiment on to a electric balance and record the mass which will decrease over time. The key characteristic of this experiement is that the enviroment is NOT airtight in order to let the gas escape.

The most common reaction used is carbonate with acid (CO2 produced).

Control variables, on top of those you mentioned, include the use of catalysts. I would always advise people to take the 'initial' rate of reaction rather than plot a volume against time graph and find the tangent at time=0. The initial rate of reaction can be found by making the time frame of the experiment so short that it will represent the intitial rate of reaction (10 - 20 seconds). So your initial rate will simply be:

volume of gas produced (cm3) or mass lost (g) / time (s) = initial rate of reaction (cm3/s) or (g/s)

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I really want to do well in these labs, but my teacher is just crazy and I'm not a good chemist...n I study in Chem SL (forced to change to SL from HL:[ )

So I need to do a chemical reaction rate design lab...I am completely clueless.

I mean, I know what the factors could be, temperature and concentration etc.

I am really really stuck :[

Please help.

Hey,

There are two main ways of measuring the rate of a reaction. Volume of gas produced, or mass lost method.

In the volume produced the thing you have to make sure about the experiment is that the enviroment is airtight. Also you must have some way of collecting the gas and measuring it (either downward displacement of water with a measuring cylinder or simply use a gas cylinder).

Mass loss is simply putting your experiment on to a electric balance and record the mass which will decrease over time. The key characteristic of this experiement is that the enviroment is NOT airtight in order to let the gas escape.

The most common reaction used is carbonate with acid (CO2 produced).

Control variables, on top of those you mentioned, include the use of catalysts. I would always advise people to take the 'initial' rate of reaction rather than plot a volume against time graph and find the tangent at time=0. The initial rate of reaction can be found by making the time frame of the experiment so short that it will represent the intitial rate of reaction (10 - 20 seconds). So your initial rate will simply be:

volume of gas produced (cm3) or mass lost (g) / time (s) = initial rate of reaction (cm3/s) or (g/s)

I double checked my textbook and is still not understanding the initial rate of reaction?

Well I need to write a design lab, so I think I'll need to be able to explain this initial rate of reaction in my intro...

thanks though!

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I double checked my textbook and is still not understanding the initial rate of reaction?

Well I need to write a design lab, so I think I'll need to be able to explain this initial rate of reaction in my intro...

thanks though!

You wont find it in your textbook unless its really well done or its a course companion for IAs. Maybe this graph will help you:

post-21678-0-03153400-1299675322_thumb.g

When we talk about the rate of reaction in general, we are refering to the 'initial' rate of reaction i.e. when time=0 and when there are 0 moles of products present. So to find this we usually plot a graph with volume and time (like the one above) to come to a graph shaped like a curve which flattens out. This is usually a tedious process bearing in mind you need a minimum of 3 repeats for each variable and that you must vary you dependent variable at least 5 times AND that you are recording the volume of gas produced every 10 seconds! So an esay way to get around this is to say that we will limit the time of our experiment to such a short peorid that the rate we get will represent the initial rate. Have a look at the lines on the graph. The longer you wait, the less steep the graph becomes, the more inaccurate the representation of the initial rate is. This is becaus the rate is being averaged out over time, by taking the volume at 2 minutes, you are taking into account the flattening bit of the curve and thus the rate you get will not represent the 'initial rate'. If you limit the time to say 15 seconds, the rate is almost the same as if it was when time=0 seconds!

I hope that all made sense.

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I just did my design lab on this topic and got an A, so i'll tell you what I did.

I did mine based on the iodine clock reaction, H2O2 + 2I- + 2H+ ---> 2H2O + I2

I did a titration method where i put Na2S2O3 in the burette, and put the reactants of the equation into a beaker along with CaCO3, in order to quench the reaction, and Starch, so a color change would appear. then i would titrate the solution until the color changed.

I did this using 5 different concentration of H2O2, each 2 trials, and then depending on the concentration of H2O2, the titration would either take longer or shorter. This would show the rate of the reaction because as concentration increases, the rate of the reaction quickens, thus producing more iodine and taking a short amount of time for the titration to work.

My IV was the concentration of the H2O2

My DV was the rate of the reaction (mol dm-3 s-1)

levels of IV: .20M of H2O2, .4M, .6M, .1M, and .05M (i used smaller concentrations to show that decreasing concentration slows a reaction and takes a longer amount of time for the titration to work)

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I did my chemistry full investigation lab report on the affect of concentration.

Independent Variable: Concentration of H2O2 solution

Dependent Variable: Rate of decomposition of H2O2

Controlled Variables: Temperature

Type of catalyst

Amount of catalyst

Presence of light

Pressure

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