My research inquiry, as the subject provinces, is How would the concentration of sulphuric acid affect the rate of H gas produced when it respond with Fe. The ground that I want to make this experiment is to turn out whether the hit theory in Chapter6.2 of the Chemistry textbook1 is true about the concentration will impact the rate of a reaction. And I besides did another widen experiment about whether temperature will impact the rate of a reaction. After a batch of computations, and analysis of the experiments data I got, my decision is the hit theory is non really suited on this peculiar experiment.
In the Chapter 6 of IB chemical science text edition about Kinetics, the factors that will impact the rate of a reaction are: Concentration, force per unit area, temperature, surface country and accelerator. I want to take one of these factors and turn out if it will really impact the reaction rate and I choose concentration.
Then I started to believe about the experiment that can demo whether the concentration of the reactants will impact the reaction rate. Because my school ‘s research lab is really limited, so I can merely make the experiments that are easy to run and will non utilize really sophisticated setup. So, after serious consideration, I decided to utilize the Fe react with sulphuric acid, the expression is elaborated below:
Fe + H2SO4 — & gt ; FeSO4 + H2
The ground that I choose to make this experiment is that this experiment can bring forth gas and the tools to make this experiment are easy to obtain. In Chapter 6 of the Chemistry text edition, one of the techniques for mensurating rate is aggregation of an evolved gas. Because the rate that the gas generated can stand for the rate of the whole reaction, so I merely necessitate to mensurate how fast does the H gas evolved.
Development of the Experiment
This experiment is non every bit simple as it looks like. The first manner I use is let Fe respond with different concentration sulphuric acid, and utilize a stop watch to mensurate the clip for each different reaction to complete. But after I give a attempt of this method, I found out that for a reaction to wholly halt will take hours or more, which means this manner wastes excessively much clip, so this method is non really practical.
The 2nd manner that came out of my head is let the H gas been evolved to make full a balloon, and see how much clip it will take to allow the balloon to detonate. But as everyone knows, Hydrogen gas can fire, so when the balloon explodes, it may besides put off the H gas, so this method is manner excessively unsafe to run.
The concluding method I developed is close to hone ( I think ) , and it is better to be shown by a exposure:
In the left portion of this exposure, the Fe and sulphuric acid will bring forth H gas ; the H gas will travel into the beaker in the center of this exposure through the gum elastic tubing. Because the beaker in the center has been filled with H2O, the H gas go into the beaker will get down to force the H2O out of the beaker. Because there is another glass tubing in the beaker ( you can see it in the exposure ) , H2O will be push into the calibrated flask in the right portion of the exposure through the glass tubing and the gum elastic tubing. I merely necessitate to mensurate the clip for certain sum of H2O that has been push into the calibrated flask, and compare the clip taken of every different reaction, I will cognize whether the concentration will impact the rate of the reaction.
Although this method is perfect for me, I still made a error when I was piecing the setup together:
As the exposure above shows, this is the beaker used to allow the reaction took topographic point. The error I made is: The glass tubing is excessively deep. Because the glass tubing is so deep that the oral cavity of the glass tubing is wholly immersed by the sulphuric acid, therefore the H gas evolved can non travel through the glass tubing, as a consequence, the H gas push the sulphuric acid into the glass tubing!
Fortunately, this error is non really difficult to rectify, I merely need to draw the glass tubing out a small spot, as the exposure shows below:
Material and instruments: pure Fe pulverization, really concentrated sulphuric acid, gas collection bottle, conelike flask, balance, stop ticker, grad cylinder, glass tubings and soft gum elastic tubings.
Because the sulphuric acid I got is really concentrated ( 98 % ) , so the first thing I need to make is fixing sulphuric acid which has different concentration.
- Use the grad cylinder to mensurate certain sum of 98 % sulphuric acid.
- Use the grad cylinder to mensurate certain sum of H2O.
- Add the sulphuric acerb really easy into the H2O and utilize a glass stirs maintain whisking the mixture. I have repeated these processs for nine times because I raised the concentration of sulphuric acid by 10 % each clip, eventually I got 9 solutions have different concentration: 10 % , 20 % , 30 % , 40 % , 50 % , 60 % ,70 % , 80 % and 90 % .
- Use the balance to mensurate precisely 5g of Fe pulverization.
- Add the Fe pulverization into the beaker on the left of the exposure.
- Add the 10 % sulphuric acid into the beaker on the left of the exposure.
- The H gas will “ imperativeness ” the H2O in the bottle into the grad cylinder and utilize the halt ticker to mensurate the clip taken for the H gas to press out certain volume of H2O.
- Add the 5g of Fe pulverization and 20 % sulphuric acid into the left beaker so repeat measure 6 and 7.
- Add the 5g of Fe pulverization and 30 % sulphuric acid into the left beaker so repeat measure 6 and 7.
- Add the 5g of Fe pulverization and 40 % sulphuric acid into the left beaker, so reiterate measure 6 and 7.
- Add the 5g of Fe pulverization and 50 % sulphuric acid into the left beaker so repeat measure 6 and 7.
- Add the 5g of Fe pulverization and 60 % sulphuric acid into the left beaker so repeat measure 6 and 7.
- Add the 5g of Fe pulverization and 70 % sulphuric acid into the left beaker so repeat measure 6 and 7.
- Add the 5g of Fe pulverization and 80 % sulphuric acid into the left beaker so repeat measure 6 and 7.
- Add the 5g of Fe pulverization and 90 % sulphuric acid into the left beaker so repeat measure 6 and 7.
- Add the 5g of Fe pulverization and 98 % sulphuric acid into the left beaker so repeat measure 6 and 7.
Data and Analysis
From the tabular array above, we can see a really unusual tendency: When the concentration of sulphuric acerb addition from 10 % to 60 % , the clip is diminishing, in other words, the rate of the reaction keeps rushing up ; but when the concentration of sulphuric acid reaches 70 % , there ‘s no reaction between Fe and sulphuric acid at all! At first, I can non even believe what I saw, so I repeat the reaction between Fe and 70 % sulphuric acid for several times but finally lead to the same consequence: Nothing happened. Then I search this unusual thing among a batch of books and web sites, and this is called passivation2.
Definition of passivation: Passivation is the procedure of doing a stuff “ inactive ” in relation to another stuff prior to utilizing the stuffs together. For illustration, prior to hive awaying H peroxide in an aluminum container, the container can be passivated by rinsing it with a dilute solution of azotic acid and peroxide jumping with deionized H2O. The azotic acid and peroxide oxidizes and dissolves any drosss on the interior surface of the container, and the deionized H2O rinses off the acid and oxidised drosss. Another typical passivation procedure of cleaning unstained steel armored combat vehicles involves cleaning with Na hydrated oxide and citric acid followed by azotic acid ( up to 20 % at 120 & A ; deg ; F ) and a complete H2O rinse. This procedure will reconstruct the movie ; take metal atoms, soil, and welding-generated compounds ( e.g. oxides ) .
In the context of corrosion, passivation is the self-generated formation of a difficult non-reactive surface movie that inhibits farther corrosion. This bed is normally an oxide or nitride that is a few atoms thick.
Mechanisms of passivation: Under normal conditions of pH and O concentration, passivation is seen in such stuffs as aluminium, Fe, Zn, Mg, Cu, chromium steel steel, Ti, and Si.
Ordinary steel can organize a passivating bed in alkali environments, as rebar does in concrete. The conditions necessary for passivation are recorded in Roubaix diagrams.
Some corrosion inhibitors help the formation of a passivation bed on the surface of the metals to which they are applied.
Passivation of specific stuffs: Aluminum may be protected from oxidization by anodising and/or valorizing ( sometimes called Anodizing ) , or any of an mixture of similar procedures. In add-on, stacked passivation techniques are frequently used for protecting aluminium. For illustration, chromating is frequently used as a sealer to a previously-anodized surface, to increase opposition to salt-water exposure of aluminium parts by about a factor of 2 versus merely trusting on anodising.
Ferric stuffs, including steel, may be slightly protected by advancing oxidization ( “ rust ” ) and so change overing the oxidization to a metalophosphate by utilizing phosphorous acid and farther protected by surface coating. As the uncoated surface is water-soluble a preferable method is to organize manganese or zinc compounds by a procedure normally known as Parkerizing or phosphate transition. Older, less-effective but chemically-similar electrochemical transition coatings included blueing, besides known as black oxide.
Nickel can be used for managing elemental F, thanks to a passivation bed of nickel fluoride.
After we read the above account of passivation, the ground why Fe does non respond with concentrated sulphuric acid is pretty clear: Because concentrated sulphuric acid is highly oxidizing, so as long the sulphuric touches the surface of Fe, it will organize an oxidised bed on the Fe and this bed will halt Fe and sulphuric acid being “ touch ” , therefore there is no reaction would happen.
An Extend of the Topic
It seems that this experiment could be end here, but there ‘s another thought came out of my head: Since concentration can non ever impact the rate of the reaction, what about the other factors? Will other factors be suited on this really peculiar instance? Then I decided to make another experiment to see whether the temperature will impact the rate of this reaction.
- Use the balance to mensurate 5 gm Fe pulverization.
- Add the Fe pulverization into a clean trial tubing.
- Add some 98 % sulphuric acid into the same trial tubing.
- Use an intoxicant burner to heat the trial tubing and detect what will go on.
Not everything goes like we expected, and this experiment is non an exclusion.
As you can see, in the exposure on page 15, there ‘s a batch of gas evolved from the trial tubing, but I can decidedly state you that this gas is non hydrogen gas, there are two grounds I can establish to turn out that this is non hydrogen gas:
- We all know that H gas can fire, right? But when I put the oral cavity of the trial tubing really closely to the fire, I ca n’t see any burning.
- We all know that H gas does n’t hold any olfactory property, but when this gas evolved, I can smell a really strong pungent and smelly olfactory properties.
This grounds can turn out this gas is non hydrogen gas, but this grounds besides leads to another inquiry: What gas is it?
I search on the cyberspace and I found an equation that may be relevant to this experiment:
2Fe+6H2SO4 ( Hot, concentrated ) =Fe2 ( SO4 ) 3+3SO2+6H2O
I besides found out the ground for why would the experiment react like the equation above in a Chinese web site, here is the interlingual rendition: When the temperature is lifting, the oxidized bed on the Fe will be destroyed and forestall this bed regenerate. Therefore, the concentrated sulphuric acid can respond with the Fe. Besides, the lifting temperature do the sulphuric acid be more oxidising than when it ‘s cold, so this straight cause the oxidization figure of Fe to increase, and this is the ground that when Fe react with hot, concentrated sulphuric acid will bring forth S dioxide ( Which is the pungent and smelly odor I mentioned in the 2nd grounds on page 16 ) .
- The Collision Theory in Chapter 6.2 of the Chemistry text edition, which states “ The rate at which atoms collide is increased by increasing the concentration of the reactants ” , is non suited on every reaction. In this instance, increase the concentration of sulphuric acid can merely increase the reaction rate in a certain scope.
- Increase the temperature of the reactants will non ever leads to the addition of reaction rate ; alternatively, increase the temperature may take to a wholly different reaction. In this instance, raise the temperature will do the Fe and sulphuric acid to respond and bring forth S dioxide, instead than H gas.
Some restriction of the experiment:
- After I know iron will non respond with 70 % sulphuric acid, I decided to make more experiments to obtain the accurate “ Reaction-Stop Concentration ” , which must be in the scope of 60 % -70 % , but because the experiments tools I have are really limited, so I can non raise the concentration by1 % at a clip as I wanted, which leaves a small spot “ defect ” to this experiment.
- Normally pupils should make experiments in the school ‘s research lab, but because of “ some ground ” , the lab ca n’t give us the chance to make the experiment, so I have to purchase the tools and stuffs and do the experiments at place, so this cause a batch of incommodiousnesss to my experiments.
Bibliography and Mentions
- Damji, Sadru and Green, John, written topographic point unknown, IBID Chemistry Book 2nd edition.
- Budinski, Kenneth G. ( 1988 ) , written at Englewood Cliffs, New Jersey, Surface Engineering for Wear Resistance, Prentice Hall.
- Brimi, Marjorie A. ( 1965 ) , written at New York, New York, Electrofinishing, American Elsevier Publishing Company, Inc.