Rate and extent of chemical change RQP- effects of concentration involving measuring the volume of gas produced

Question 1

apparatus setup

Answer 1

• conical flask with dilute acid and magnesium ribbon in it with a delivery tube in it and closed off with a bung
• delivery tube bent down into a trough (box) with water in
• measuring cylinder in the water held up with a clamp stand
• water going up into measuring cylinder

Question 2

step 1

Answer 2

measure 50cm3 of 2.0M hydrochloric acid using one of the measuring cylinders. pour the acid into the 100cm3 conical flask

Question 3

step 2

Answer 3

set up the apparatus as shown in the diagram

Question 4

step 3

Answer 4

half fill the trough or bowl with water

Question 5

step 4

Answer 5

fill the other measuring cylinder with water. Make sure it stays filled with water when you turn it upside down

Question 6

step 5

Answer 6

when you’re ready, add a 3cm strip of magnesium ribbon to the flask, put the bung back into the flask as quickly as you can, and start the stopclock

Question 7

step 6

Answer 7

record the volume of hydrogen gas given off at suitable intervals (eg 10secs) in a table

Question 8

step 7

Answer 8

continue timing until no more gas appears to be given off

Question 9

step 8

Answer 9

repeat using 1.0M hydrochloric acid

Question 10

what is the independent variable of this experiment?

Answer 10

concentration (mol/dm3)

Question 11

what is the dependent variable of this experiment?

Answer 11

volume of hydrogen gas (cm3)

Question 12

what are the control variables of this experiment and how can we control them?

Answer 12

• mass of magnesium- cut each piece to 3cm
• temperature- do in the same room at the same temperature
• volume of acid- use measuring cylinder