Required Practical 5: Investigating Rates Of Reactions

Question 1

This practical measures the volume of gas produced. It focuses on rate of reactions. What are this practical’s reactants and what are this practical’s products?

Answer 1

Magnesium is a reactant. It’s added to HCL acid and hydrogen gas is produced.

Question 2

What is symbol equation for this practical? (hint: magnesium + hydrochloric acid -> magnesium chloride + hydrogen)

Answer 2

Mg (g) + 2HCL (aq) -> MgCl2 (aq) + H2 (g)

Question 3

How could gas be collected and measured in his practical?

Answer 3

It’s collected by the water trough and measuring cylinder together, but measured using the measuring cylinder.

Question 4

What’s the aim of this practical?

Answer 4

To investigate how the concentration of HCL acid affects the rate of this chemical reaction

Question 5

What is the independent variable and what is it in this practical?

Answer 5

The independent variable is the variable that changes each time we do the practical for results (like repeat the steps). In this practical, it’s the concentration of HCL acid

Question 6

Define dependent variable and tell me what the dependant variable for this practical is

Answer 6

Dependant variable: variable that we’re measuring throughout the course of the practical. In this one, the dependant variable is the time taken for Hydrogen to form or time taken for magnesium to be used up

Question 7

What are the control variables for the practical?

Answer 7

We keep the same length of magnesium ribbon used
We keep the same amount of water in the measuring cylinder
We keep the same volume of HCL used

Question 8

What is the first step of this practical?

Answer 8

Measure out 50 cm3 of 2.0 M hydrochloric acid using a measuring cylinder. Once it’s been measured transfer the acid to a 100 cm3 conical flask

Question 9

What’s the second step in this practical?

Answer 9

Start setting up the apparatus. Fill the trough/bowl up with water to its halfway point.

Question 10

What’s the third step of this practical?

Answer 10

Fill a measuring cylinder up all the way up with water and turn it upside down (without spilling any) and place it (upside down) into the trough of water with a delivery tube and a bung connecting it to the conical flask of acid

Question 11

What’s the fourth step of the practical?

Answer 11

Once the delivery tube and measuring cylinder is set up, lift up the bung, quickly place the magnesium strip in the acid, and put the bung back on immediately after that. Start the stopwatch.

Question 12

What’s the fifth step of this practical?

Answer 12

Record the volume of hydrogen gas collected at suitable intervals (every 10 seconds) into a results table. Do that until it appears no more gas will be given off. Stop recording

Question 13

What is the sixth and final step of this practical?

Answer 13

Repeat steps one to five, this time using 1.0 M of acid (less conc. than before) then plot a graph of results

Question 14

Define the term random error and tell me what the radon errors in this practical were

Answer 14

Random error: an unpredictable difference/error/mistake caused by things such as human errors in measuring. In this experiment:
You could’ve taken down your results a second too late/at wrong timings/at inconsistent intervals OR placed your bung back into the conical flask too slowly and let some hydrogen gas escape.

Question 15

Describe using kinetic/collision theory why increasing the concentration of acid allowed for a faster rate of reaction.

Answer 15

Collision/kinetic theory states that for a reaction to happen, particles must collide with enough energy and frequency. For the collisions to meet this criteria often enough for a fast reaction, you can implement one of the 4 factors that speed rate up. We picked concentration for this practical. More concentration means more particles gathered in a given volume. Because there are now more particles and it’s crowded, particles have no choice, but to collide more frequently and since they collide frequently, it’ll be more common for a collision over the activation energy to happen. This allows for more frequent, successful collisions which results in faster rates of reactions.

Question 16

State two reasons why the curve for the higher concentration of acid might’ve reached a lower height than the curve with a lower conc. of acid

Answer 16

A human error might have been made concerning letting hydrogen gas escape or getting the wrong measurements are the wrong timings. OR because one of the reactants has been used up before more gas could be produced. Because the reaction is going so fast (cause we have higher concentration) we don’t get the chance to use up all of the acid (with the high conc. and all) but we do use up all of the magnesium.