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How does the concentration of HCl affect the rate of reaction with CaCO3?

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Introduction

´╗┐Tinaye Mandishona Chemistry Investigation ? How does concentration affect rate of reaction? In this experiment we are looking at how concentration affects rate of reaction. We are reacting 0.5 grams of marble (CaCO3) with different concentrations of hydrochloric acid (HCL- 0.25 molar ? 1.5 molar). When you react marble (CaCO3) with Hydrochloric acid (HCl) you produce Calcium Chloride (CaCl2), Carbon dioxide (CO2) and water (H2O). CaCO3(s)+ 2HCl(aq) = CaCl2(aq)+ CO2(g)+ H2O(l) Variables: Control variables: * Temperature ? temperature can increase the rate of reaction so in our experiment we are going to try keep the temperature the same (will be explained in more detail how it affects rate of reaction in the bottom half of introduction). * Surface area ? If we increase the surface area of our reactants we increase the rate of reaction so therefore we will keep the surface area of the reactants the same (will be explained in more detail how it affects rate of reaction in the bottom half of introduction). * Time ? We are keeping the time at 1 minute because we used powdered marble so the reaction went very fast because the surface area was very large therefore we decided to make time one of our control variables. * Catalysts ? We are not adding any catalyst to our experiment, this is to see how our independent variable has an effect by itself on the rate of reaction. Dependant variable- * Volume of carbon dioxide produced ? we measured the amount of carbon dioxide produced because this was the only product made that we were able to extract with the equipment we were given. Independent variable- * Concentration ? We decided to make our independent variable concentration because we found it more manageable to test and we were not allowed to use catalysts. Collision theory explains why chemical reactions occur and why they react at different rates. ...read more.

Middle

49.2. We were not washing out our apparatus at first but then we started to wash them out so we could get rid of any kind of contaminates in the apparatus. We used tap water at first but then we used distilled water because distilled water is pure water, only containing H2O so eliminating any chances of contaminates unlike tap water which contains minerals such as phosphorous etc which could affect our experiment. We noted down the temperature for the reactants before and after the experiment because we couldn’t keep the temperature constant. concentration (molar) volume of carbon dioxide produced (cm³) average amount of carbon dioxide produced time (seconds) rate of reaction (cm³/seconds) 1 2 3 4 key 0.25 17.50 17.70 17.60 N/A 17.60 60.00 0.29 N/a = not applicable 0.50 27.80 26.20 27.20 29.10 27.07 60.00 0.45 anomalous result 0.75 31.00 32.50 30.50 N/A 31.33 60.00 0.52 1.00 34.30 35.60 36.70 N/A 35.53 60.00 0.59 1.25 41.20 42.20 41.70 N/A 41.70 60.00 0.70 We only had one anomalous results which was 29.10, this could have occurred from either using more than 0.5 grams of powdered marble or not washing out the buckler flask properly, leaving contaminates to react with the hydrochloric acid, using tap water instead of distilled water to wash out the apparatus or we could have used the wrong concentration in the experiment. The graph shows us that as you increase the concentration, there is more hydrogen being made. The r² value also tells us that our results are very accurate because the r² value is close to 1 (0.9744). The R² value tells us how our results fit the line of best fit, if the r² is one, then our results fit the line of best The R² value tells us how our results fit the line of best fit, if the r² is one, then our results fit the line of best fit perfectly, making our results very accurate good making our results very accurate. ...read more.

Conclusion

The average amount of carbon dioxide produced goes up by approximately 3-4 cm³ as you move up from 0.25-1.5 molar. My spread of data for my preliminary work is very bad because the results were too far apart from each other having an effect on the averages so my results wouldn’t be considered very accurate and reliable, if you look at my preliminary graphs my first two points of data are far off the line of best fit unlike the other points which nearly fit the line of best fit .But my main result’s spread of data is very good, with me repeating one of my results just to get a better spread of data with the majority of my results fitting the line of best fit. I feel my results are quite reliable because I repeated my experiment when I got anomalous results, I repeated my experiment three times also I got a good spread of results for my main results, but my results could be considered unreliable and inaccurate due to no care taken on my preliminaries because I didn’t make sure the range of my results was very good and my average result for 0.25 m is nearly 10cm³ less than my average results for 0.50m, meaning something wrong happened because all the other results are 3-4 cm³ apart. Conclusion: I can make the right conclusion for my results because the range of results and spread of data for my main results are quite good, my results are also quite reliable because I repeated them 3 times and even repeated my experiment when I got anomalies, the fact I got anomalies ruins the chances of my results being very good because by getting anomalies my method has flaws in it. There thing preventing me from getting a totally good conclusion are the anomalies because some of them are out of the range of the data and also I didn’t take my preliminaries as serious as my main results resulting in an odd string of results for 0.25 molar which doesn’t fit the pattern of my other results. ...read more.

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