Rates Of Reaction 2 (Collecting Gas) - GCSE Science Required Practical

Summary

Mr. Mitchell's video from Mars for Science explores two methods for measuring the rate of a chemical reaction: using a measuring cylinder and a gas syringe. He demonstrates the reaction between magnesium and hydrochloric acid at two concentrations: 2 moles per decimeter cubed and 1 mole per decimeter cubed. The video shows how to accurately measure gas production every 10 seconds and discusses the importance of precision and potential sources of error in the experiment.

Takeaways

• 🧪 Mr. Mitchell introduces two methods for measuring the rate of a chemical reaction involving magnesium and hydrochloric acid.
• 📏 The first method uses a measuring cylinder to measure the volume of gas produced by the reaction.
• 🌡️ The second method employs a gas syringe to track the gas volume, providing an alternative to the measuring cylinder.
• 🔬 Two different concentrations of hydrochloric acid are compared: 2 moles per decimeter cubed and 1 mole per decimeter cubed.
• 💧 Hydrochloric acid is measured in a conical flask using a measuring cylinder and pipette to ensure accuracy.
• 🕒 The reaction is timed and the volume of gas produced is recorded every 10 seconds.
• 📊 A graph is used to compare the reaction rates, with time on the x-axis and gas volume on the y-axis.
• ⚖️ The reaction stops when all the magnesium has reacted, as it is the limiting reactant.
• 🔍 Potential sources of error are discussed, including timing inaccuracies and the imprecision of the measuring cylinder.
• 🔬 An inverted burette is suggested as a more precise tool for measuring gas volume, allowing for more accurate results.

Q & A

What are the two methods Mr. Mitchell demonstrates for measuring the rate of a chemical reaction?

Mr. Mitchell demonstrates using a measuring cylinder and a gas syringe as the two methods for measuring the rate of a chemical reaction.

Which reactants are used in the experiment to measure the rate of a chemical reaction?

The reactants used in the experiment are magnesium and hydrochloric acid.

What are the two different concentrations of hydrochloric acid that Mr. Mitchell compares?

Mr. Mitchell compares two moles per decimeter cubed (2 M) against one mole per decimeter cubed (1 M) concentrations of hydrochloric acid.

How does the concentration of hydrochloric acid affect the rate of reaction?

A higher concentration of hydrochloric acid, such as 2 M, results in a faster rate of reaction compared to a lower concentration like 1 M.

What is the purpose of inverting the measuring cylinder filled with water during the experiment?

Inverting the measuring cylinder filled with water is to displace the gas produced during the reaction, allowing for the measurement of gas volume.

Why is it important to keep the gas syringe dry during the experiment?

The gas syringe needs to be kept dry to prevent the plunge from getting stuck, which would hinder the measurement of gas produced.

How often should the volume of gas produced be measured during the experiment?

The volume of gas produced should be measured every 10 seconds during the experiment.

What is the significance of the steepness of the curve on the graph in relation to the rate of reaction?

A steeper curve on the graph indicates a faster rate of reaction, as it shows a greater volume of gas being produced in the same amount of time.

Why does the reaction stop even though there is an excess of hydrochloric acid?

The reaction stops when all of the magnesium, the limiting reactant, has reacted, regardless of the excess hydrochloric acid.

What are some sources of error mentioned in the script that could affect the accuracy of the experiment?

Sources of error include the difficulty of starting the timer, putting the bung in, and adding magnesium simultaneously, and the imprecision of the measuring cylinder which can only read every one centimeter cubed of gas collected.

Why might using an inverted burette be more precise than a measuring cylinder in this experiment?

An inverted burette is more precise because it allows for readings of every 0.1 centimeter cubed of gas collected, providing a greater degree of precision in the results.

Outlines

00:00

🔬 Measuring Chemical Reaction Rates

In this educational video, Mr. Mitchell introduces viewers to the process of measuring the rate of a chemical reaction, focusing on two methods: using a measuring cylinder and a gas syringe. He explains that the experiment involves a reaction between magnesium and hydrochloric acid, comparing two concentrations: 2 moles per decimeter cubed and 1 mole per decimeter cubed. The video demonstrates how to accurately measure and pour the hydrochloric acid into a conical flask, ensuring precision by reading at eye level and using a pipette for the final drops. The first method shown involves inverting a measuring cylinder filled with water to capture the gas produced by the reaction, with careful attention to avoiding air bubbles and ensuring the cylinder is clamped securely. The gas production is measured every 10 seconds, and the process is repeated with the lower concentration of hydrochloric acid to observe differences in reaction rates. An alternative method using a gas syringe is also introduced, emphasizing the need to keep the syringe dry to prevent errors. The video concludes with a discussion on how to graph the results, comparing the rates of reaction based on the steepness of the curves on the graph, and highlights potential sources of error in the experiment, such as the imprecision of the measuring cylinder and the difficulty in coordinating the start of the reaction.

Keywords

💡Chemical Reaction

A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. This is the central theme of the video, where Mr. Mitchell demonstrates how to measure the rate at which a chemical reaction occurs. In the script, chemical reactions are exemplified by the reaction between magnesium and hydrochloric acid, which produces hydrogen gas.

💡Rate of Reaction

The rate of reaction refers to the speed at which a chemical reaction proceeds. It is a fundamental concept in chemistry and is the focus of the video. Mr. Mitchell uses two different concentrations of hydrochloric acid to compare the rates at which the reactions with magnesium occur, showing that a higher concentration leads to a faster reaction.

💡Measuring Cylinder

A measuring cylinder is a piece of laboratory equipment used to measure the volume of liquids. In the video, Mr. Mitchell uses a measuring cylinder to measure out specific volumes of hydrochloric acid and to collect the gas produced during the reaction. The cylinder is filled with water and inverted to measure the volume of gas displaced by the reaction.

💡Gas Syringe

A gas syringe is a tool used to collect and measure gases. In the video, it is presented as an alternative method to the measuring cylinder for measuring the volume of gas produced during the reaction. The script describes how to use the gas syringe to collect gas and measure it every 10 seconds.

💡Hydrochloric Acid

Hydrochloric acid is a strong acid commonly used in various chemical reactions. In the video, it is one of the reactants in the reaction with magnesium. Mr. Mitchell uses two different concentrations of hydrochloric acid (2 moles per decimeter cubed and 1 mole per decimeter cubed) to demonstrate the effect of concentration on the rate of reaction.

💡Magnesium

Magnesium is a metallic element that is highly reactive, especially with acids. In the video, it is the reactant that reacts with hydrochloric acid to produce hydrogen gas. The script describes how magnesium is added to the conical flask containing hydrochloric acid to initiate the reaction.

💡Concentration

Concentration in chemistry refers to the amount of a substance present in a given volume of solution. The video script discusses how concentration affects the rate of a chemical reaction, with higher concentrations of hydrochloric acid leading to faster reactions, as demonstrated by comparing 2 moles per decimeter cubed to 1 mole per decimeter cubed.

💡Volume of Gas

Volume of gas is a measure of the space occupied by a gas. In the context of the video, the volume of gas produced is used as a measure of the rate of the chemical reaction between magnesium and hydrochloric acid. The script describes how the volume of gas is measured at regular intervals using a measuring cylinder and a gas syringe.

💡Reaction Rate Graph

A reaction rate graph is a graphical representation of the rate at which a chemical reaction proceeds over time. In the video, Mr. Mitchell instructs on how to plot the volume of gas collected against time to create a graph that illustrates the rate of reaction. The steepness of the curve on the graph is indicative of the reaction rate, with a steeper curve for the 2 molar hydrochloric acid indicating a faster reaction.

💡Limiting Reactant

The limiting reactant is the reactant that is completely consumed when the reaction is complete, thus limiting the amount of product formed. In the video, magnesium is identified as the limiting reactant in the reaction with hydrochloric acid, as the reaction stops when all the magnesium has reacted, regardless of the amount of hydrochloric acid present.

💡Sources of Error

Sources of error refer to factors that can cause discrepancies between the expected and actual results of an experiment. The script mentions potential errors such as the imprecision of the measuring cylinder and the possibility of hydrogen gas being lost at the start of the reaction, which can affect the accuracy of measuring the rate of the chemical reaction.

Highlights

Introduction to measuring the rate of a chemical reaction using two methods: a measuring cylinder and a gas syringe.

Demonstration of using magnesium and hydrochloric acid for the reaction.

Comparison between two different concentrations of hydrochloric acid: 2 moles per decimeter cubed and 1 mole per decimeter cubed.

Procedure for measuring 50 centimeters cubed of 2 molar hydrochloric acid using a measuring cylinder.

Technique for eliminating air bubbles in the measuring cylinder by inverting it under water.

Instructions on clamping the measuring cylinder and recording gas production every 10 seconds.

Use of a delivery tube to direct the gas into the measuring cylinder.

Observation that the 2 molar hydrochloric acid produces gas faster than the 1 molar.

Alternative method using a gas syringe to measure gas production.

Importance of keeping the gas syringe dry to avoid errors.

Methodology for collecting data on gas production every 10 seconds.

Graphing results with time on the x-axis and volume of gas on the y-axis.

Explanation of how the reaction rate is indicated by the steepness of the curve on the graph.

Understanding that the reaction stops when the limiting reactant, magnesium, is fully reacted.

Identification of potential sources of error, such as timing inaccuracies and hydrogen loss at the start of the reaction.

Discussion on the imprecision of the measuring cylinder and the benefits of using an inverted burette for greater precision.

Transcripts

hi there it's mr. Mitchell here from

Mars for science and today we'll be

looking at the second of two videos

measuring a rate of a chemical reaction

I'm going to show you two methods to

measure the rate of a chemical reaction

today firstly using a measuring cylinder

and secondly a gas syringe for action

today I'm going to using magnesium and

hydrochloric acid I'm going to be

comparing two different concentrations

of hydrochloric acids I'm going to be

looking at two moles per decimeter cubed

against one mol per decimeter cubes 2

mol per decimeter cubed means for every

decimates acute of water I have every

litre of water

I am dissolving two models of

hydrochloric acid in the solution I'm

going to start by measuring 50

centimeters cubed of 2 mol per decimeter

cubed hydrochloric acid in a measuring

cylinder I'm going to pour the first 45

making sure I read at eye level to see

the bottom of the meniscus as I get

close I'm going to use a pipette to add

the final few drops I'm going to pour

the hydrochloric acid into a conical

flask with a bung and delivery tube the

first method I'm going to show you is a

measuring cylinder filled with water and

inverted that the gas will displace as

it's produced push the measuring

cylinder into the trough and then slowly

lower the top of the measuring cylinder

down to fill it with water this will

eliminate the risk of getting any air

bubbles in the measuring cylinder you

then need to clamp the measuring

cylinder in place about one centimeter

off the bottom of the trough make sure

that you can see the scale on the

measuring cylinder because you're going

to need to record the gas being produced

every 10 seconds put the delivery tube

into the bottom of the measuring

cylinder like so

you're going to add the magnesium to the

conical flask and as you do this your

part is going to start the stop clock at

the same time you're going to have to

put the bunk immediately onto the top of

the conical flask making sure there's no

room for the gas to escape as the gas is

produced water is forced out to the

measuring cylinder you need to count how

much gas has been produced every 10

seconds and record it in your results

table this time I'm using the 1 molar

hydrochloric acid to see if the

reactions are little bit slower I'm

going to once again pour the

hydrochloric acid into the conical flask

and as you add the magnesium into the

burners start the timer at the same time

once again we're measuring the gas

produced every 10 seconds

an alternative method is to use a gas

syringe we're still using a conical

flask bung and delivery tube with the

hydrochloric acid in magnesium however

you're measuring how much gas fills up

the gas syringe

once again measuring the amount of gas

produced every 10 seconds

the gas syringe needs to be kept dry at

all times otherwise there's a risk of

the plunge getting stuck and you won't

be able to get any results

now you've collected results of

different concentrations you're going to

draw a graph of your results on your

graph you'll have time along the x-axis

in seconds and volume of gas collected

every 10 seconds in centimeters cubed

on the y-axis as you can see the two

molar hydrochloric acid has a much

steeper curve than the 1 molar

hydrochloric acid therefore has a faster

rate of reaction the results reach the

same point that's because we use an

excess of hydrochloric acid for this

reaction that means that the magnesium

is the limiting reactant the reaction

will stop when all of the magnesium has

reacted and so that means there's only a

certain volume of gas that can be

produced there are some sources of error

to be aware of in this reaction firstly

the fact that we are starting the timer

putting the bung in the conical flask

and adding the magnesium all at the same

time is impossible this means it's going

to have you and a partner doing this

reaction as it be very difficult on your

own also some hydrogen may be lost at

the start of the reaction and that the

source of error is that the measuring

cylinder is quite imprecise because we

can only read every one centimeter cubed

of gas that's collected if we were to

use an inverted burette this would be

much more precise as we can see every

naught point 1 centimeter cubed of gas

collected and therefore have a greater

degree of precision in our result