Investigate the factors, which affect the rate of reaction between Calcium carbonate and Hydrochloric acid
Background information


In this investigation, which is about the different factors and their affects on the rate of reaction, we will be reacting calcium carbonate and hydrochloric acid.


The equation for this reaction is:


Calcium Carbonate + Hydrochloric acid ΰ Calcium Chloride + Water + Carbon dioxide


CaCO3 (s) + 2HCl (aq) ΰ CaCl2 (aq) + H2O (l) + CO2 (g)


We will be using hydrochloric acid because it is a strong acid and is fully dissociated when put in water. Hydrochloric acid forms when hydrogen chloride gas is dissolved in water.


HCl(g) + H2O(l) ΰ H+ (aq) + Cl- (aq)


In weak acids there is only a partial dissociation occurs, that is only some of the molecules split up into ions


CH3COOH (l) + H2O (l) « CH3COO- (aq) + H+ (aq)


Variables


In any reaction there are several factors, which could cause the reaction to speed up or slow down.


The variables that may have an affect on this experiment are:


· Size of marble chip- the size of the marble chip will affect our experiment because this dictates the surface area. The larger the surface area the more calcium carbonate lattice is exposed to the Hydrogen and chloride ions in the acid therefore there will be more collisions more will be successful so the rate of the reaction will be faster.


· Concentration of hydrochloric acid- this is the proportion of hydrochloric acid in the solution. This affects the rate of reaction because you could be increasing the amount of hydrogen ions and chloride ions in the solution, which again increases the likelihood that more successful collisions will occur therefore the rate of reaction will be faster.


· Temperature- the temperature adds energy to the reaction an affects how quickly the particles move. By doing this temperature affects the number of affective collisions the more affective collisions that occur the faster the reaction.


To make this a fair test we will have to keep all variables the same except the one we are investigating. The variable I have chosen to investigate is the concentration of the hydrochloric acid. To change the concentration of the hydrochloric acid we will make a series of dilutions from a stock bottle containing 2M Hydrochloric acid. To measure the rate of reaction we will be measuring the volume of carbon dioxide produced. The size of the marble chips available will be small and large. To produce a good supply of gas small chips will be used. The highest concentration available in the experiment is 2 molar. The table shows how I will control the other factors that could affect the rate of reaction so that I know my results will be reliable and reflect the affect of concentration only on the rate of my reaction.

Controlled Variable
Value

Size of marble chips
small


Total volume of acid solution


50 ml


Mass of marble chip


20 grams


Temperature


Room temperature


Light intensity


Lab conditions


Independent variable


I will change the concentration of the acid. To get reliable results I need to chose a good range of dilutions. I will make 5 different dilutions of hydrochloric acid from a stock bottle provided which is of Known concentration i.e. 2M.


Below is a table, which shows the ratio of water to hydrochloric acid I will use to get my 5 different results so I can draw a graph.


Volume of hydrochloric acid (cm3)


Volume of Distilled water (cm3)


50


0


40


10


30


20


20


30


10


40


Dependant variable


In this reaction we can trace the rate by looking at the amount of carbon dioxide gas that is produced. I will collect the gas that is produced in the initial stage of the reaction. I will time using an electronic stop clock how long it takes to produce 100cm3 of the gas.


Equipment


· Burettes – We will be using the burette because we can measure to the nearest cm³.


· Gas Syringe – We choose this because it will be used to collect the gas.


· Side Arm Conical Flask – This used so the gas syringe can be connected up to it.


· Electronic Balance – To weigh the mass accurately to 2 decimal places.


· Filter Funnel – to fill the burettes safely.


· Calcium Carbonate


· Hydrochloric acid


· Distilled Water – to change the concentration of the hydrochloric acid.


· Filter paper – it there to have something to weigh the chips on


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