Required Practicals - Rates of Reaction

Question 1

What is the goal of the rates of reaction practical?

Answer 1

To find out how the concentration of an acid affects the rate of reaction.

Question 2

What is the apparatus list for the rates of reaction practical?

Answer 2

-safety goggles
-100cm3 conical flask
-a single-holed rubber bung and delivery tune to fit conical flask
-water trough
-two 100cm3 measuring cylinders
-clamp stand
-stop clock
-magnesium ribbon cut into 3 cm lengths
-two different concentrations of dilute hydrochloric acid, 1.0 mol/dm3 and 1.5 mol/dm3.

Question 3

What is the method for the rates of reaction practical?

Answer 3

-Measure 50cm3 of 1.0mol/dm3 hydrochloric acid using a measuring cylinder. Pour the acid into the 100cm3 conical flask.
-Fit the bung and delivery tube to the top of the flask
-Half fill the trough or bowl with water
-Fill the other measuring cylinder with water. Make sure it stays filled with water when you invert it into the water trough and that the delivery tube is positioned correctly.
-Add a single 3cm strip of magnesium ribbon to the flask, put the bung back into the flask as quickly as you can and start the stopclock.
-Record the volume of hydrogen gas given off in a table.
-Repeat using 1.5 mol/dm3 hydrochloric acid.

Question 4

Why does the rate of reaction increase with higher concentration?

Answer 4

In terms of collision theory, in a more concentrated solution, particles are closer togther thus more collisions occur per unti of time, thus rate of reaction is higher.

Question 5

What is a hypothesis?

Answer 5

A proposal that could explain a fact or an observation.

Question 6

What is the equation for the disappearing cross reaction?

Answer 6

Sodium thiosulfate solution + hydrochloric acid –> Sulfur

Question 7

What does sulfur do in the disappearing cross practical?

Answer 7

It makes the solution turn cloudy.

Question 8

What is turbidity?

Answer 8

How cloudy something is

Question 9

What do we do first in the disappearing cross practical?

Answer 9

Use a measuring cylinder to put 10cm3 of sodium thiosulfate solution into a conical flask

Question 10

What do we place the conical flask with sodium thiosulfate on in the disappearing cross practical?

Answer 10

Onto a printed black cross

Question 11

What do we add to the conical flask after placing it on top of the black cross in the disappearing cross practical?

What do we do afterwards?

Answer 11

10cm3 of hydrochloric acid.

Swirl the solution and start a stopwatch.

Question 12

When do we stop the clock in the disappearing cross practical?

Answer 12

When the cross is no longer visible at all.

Question 13

How do we repeat the disappearing cross practical?

Answer 13

By using lower concentrations of sodium thiosulfate solution each time

Question 14

What should you do for each concentration of sodium thiosulfate solution?

Answer 14

Repeat the experiment and calculate a mean for each concentration

Question 15

What do we do to anomalous results when calculating a mean?

Answer 15

We discard them

Question 16

When is a measurement reproducible?

Answer 16

If it can be repeated by another person or using a different technique or equipment to get the same result.

Question 17

What is the problem with the disappearing cross practical?

Answer 17

People have different eyesights so some people can see the cross for longer and may not get the same results

Question 18

What is the reaction for the gas volume practical?

Answer 18

Magnesium + hydrochloric acid –> magnesium chloride + hydrogen

Question 19

What are we testing for in the gas volume practical?

Answer 19

The amount of gas produced per unit of time

Question 20

What is the first step of the gas volume practical?

Answer 20

Use a measuring cylinder to place 50cm3 of hydrochloric acid into a conical flask

Question 21

What do we attach the conical flask to in the gas volume practical?

Answer 21

Attach the conical flask to a bung and delivery tube.

Question 22

What do we place the delivery tube into in the gas volume practical?
What else do we place within this?

Answer 22

A container filled with water.
Place an upturned measuring cylinder in the water over the delivery tube.

Question 23

What do we add to the hydrochloric acid to start the gas volume practical?

What do we do after?

Answer 23

A 3cm strip of magnesium

Start a stopwatch

Question 24

Where is hydrogen gas trapped in the gas volume practical?

Answer 24

In the upside-down measuring cylinder

Question 25

How often do we measure the volume of hydrogen gas in gas volume practical?

Answer 25

Every ten seconds

Question 26

How do we repeat the gas volume practical?

Answer 26

Use different concentrations of hydrochloric acid

Question 27

How does concentration affect rate of reaction?

Answer 27

The greater the concentration, the faster the reaction takes place.

Question 28

Why are the rate of reaction practicals reproducible?

Answer 28

The result is the same for two different methods.