core practical 14: finding the activation energy of a reaction

Question 1

general summary

Answer 1

use initial rates method to find effect of temperature changes on rate of x reaction

Question 2

method:

Answer 2

• add solutions to 2 different test tubes
• put in water bath at 20 degrees, and wait for them to reach same temp
• add one to the other and start stop clock
• record time for colour change
  -repeat for 30-60 degrees
  rate = 1/time

Question 3

graph

Answer 3

• plot 1/Temperature (kelvin) x axis
• ln rate(ln 1/TIME) y axis
• m = -Ea/r

Question 4

assumption so we can use 1/time for rate

Answer 4

conc reached is the same

Question 5

why can we use ln (rate)

Answer 5

proprtional to rate constant (k)

Question 6

arrhenius equation

Answer 6

k = Ae ^(-Ea/RT)
k =rate constant
A = arrhenius constant
e = e
Ea = activation energy
R = 8.31
T = temperature in kelvin

Question 7

how do you get to the end point

Answer 7

• BrO3 - +5Br- + 6H + = 3Br2 + 3H2O
• 3Br2 + C6H5OH = C6H2Br3OH + 3HBr
• in test tube 1 is phenol and bromide/bromate
• in test tube 2 is sufluric acid
• u add them together
• bromate oxidises br- to br2
• bromine reacts w phenol
• when the phenol is used up, bromine is no longer removes, so it !!!!!bleaches the methyl red indicator !!!!!! at the end of the reaction