How Does Rate of Concentration Affect the Rate of Reaction Between Marble Chips and Hydrochloric Acid?

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How does rate of concentration affect the rate of reaction between marble chips and hydrochloric acid?

Introduction

We are going to investigate how the rate of reaction differs using varying concentrations of hydrochloric acid with marble chips.

Prediction

I think that the higher the molarity of the hydrochloric acid, the faster the reaction will occur because the less water molecules means the chances of acid and calcium carbonate particles colliding is greater. (If the acid was more dilute, it would contain more water molecules, meaning it would take longer for the particles to react with each other because the odds are reduced of them colliding.

Planning

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

Calcium + Hydrochloric Calcium Water + Carbon

Carbonate Acid Chloride Dioxide

To ensure a fair test, the following must be considered:

* Temperature - to keep it the same or change it, reactions go faster under a higher temperature because the heat provides the particles with energy so they move faster and the collision factor is increased. However our experiment is to see if concentration affects the rate of reaction, not temperature so it must be kept as a controlled variable. Trusting the thermostat or central heating of the classroom, it should be kept at a regular temperature, suitable for a working environment.

* Volume of acid - this must be a controlled variable also, but should be in excess otherwise the rate of reaction cannot be measured if all the acid reacted before all the marble had reacted, we would never know where in the reaction the acid ran out.

* How we measure the rate of reaction - several methods were tried in our preliminary investigations, we tried using a boiling tube upturned and submerged, so that when the gas was tubed into it the water was displaced by carbon dioxide from the reaction. However the amount of gas a boiling tube can collect is very rapid and something bigger was needed... We chose a beaker upturned, (submerged in water) and we would stop when 200cm3 of gas was collected and then we would stop the stopwatch that recorded the length of time this took.

The reason why we found the glass syringes undesirable was because despite the smooth flow of the plunger there was too much room for blunder. For example gas could escape because the syringe has more than one part to it - unlike a beaker and inertia means the gas will have to collect until it compresses enough to depress the plunger, making a fault in the time recording.
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* Balance - use the same balance to measure the chips, the room for error increases if we use different scales, to maintain a fair test the same balance must be used, and all equipment must be the same as well. The weight will be recorded in grams.

From our preliminary investigation, when we realised the acid should be in excess and not the chips, we decided to drop the value from 10g to 5g. This is for scientific and economical reasons, there were only so many marble chips available, we also decided before as a ...

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