required practical 7b- continuous monitoring method (reaction between Mg and HCl)

what is this reaction used to investigate

effect of varying concentration of acid whilst keeping temperature constant

method

1. add 50 cm³ of 0.8 moldm^-3 hydrochloric acid to a conical flask

2. set up gas syringe

3. add 6cm strip of Mg ribbon to the conical flask, place bung and start timer, swirling flask every few seconds

4. record volume of H₂ gas produced every 15s for 2.5 mins

5. alter concentration of HCL and repeat steps 1-4

analysis

• plot graph of volume oh hydrogen produced (y-axis) against time (x-axis) for each HCL concentration

• draw tangent to each line of best fit at t=0s

• calculate gradient of tangent to deduce initial rate

sources of error

• human error- delay in starting timer, reading errors on gas syringe, measuring cylinder

• temperature changes

• magnesium surface oxidised- slower reaction

• loss of gas if apparatus not gas tight