# Biology rate of reaction question

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#1
The action of the enzyme catalase is shown below.
A student investigated the effect of hydrogen peroxide concentration on the rate of
this reaction. He used catalase from potato tissue.
The student:
• put five potato chips in a flask
• added 20 cm3 of 0.5 mol dm–3 hydrogen peroxide solution to the flask
• measured the time in seconds for production of 10 cm3 of oxygen gas
• repeated this procedure with four different concentrations of hydrogen
peroxide solution.

table is in q7.1 in this link:
https://pmt.physicsandmathstutor.com...20AS-level.PDF

7.3) The student gave the maximum rate of reaction a value of 1.0 arbitrary units.
Complete Table 5 by calculating the rate of reaction in arbitrary units at each
hydrogen peroxide concentration. Record the rates using an appropriate number of
significant figures.

Here is the mark scheme:
https://pmt.physicsandmathstutor.com...20AS-level.PDF

Why did they divide 6/time?
0
7 months ago
#2
because in the previous table you had to solve, to get the Rate of reaction
/ arbitrary units and the and in 7.3 the maximum rate of reaction is the value of 1.0 arbitrary units. If u refer back to the table , 1.0 arbitrary units has the 'Time for production of 10 cm3 of oxygen gas / seconds' containing 1.0, by 6. So 6 will be mainly used throughout.
0
#3
(Original post by scrk009)
because in the previous table you had to solve, to get the Rate of reaction
/ arbitrary units and the and in 7.3 the maximum rate of reaction is the value of 1.0 arbitrary units. If u refer back to the table , 1.0 arbitrary units has the 'Time for production of 10 cm3 of oxygen gas / seconds' containing 1.0, by 6. So 6 will be mainly used throughout.
Ah I see, I get it now thanks
0
7 months ago
#4
Hi I still don't understand why 6 would be used
0
4 months ago
#5
Same here I still cannot see why that would be the reason to divide the time by 6. Can someone break it down step by step please.
0
4 months ago
#6
(Original post by befairhuman)
Same here I still cannot see why that would be the reason to divide the time by 6. Can someone break it down step by step please.
From the experimental data, the time to produce 10cm3 of oxygen gas plateaus at 6, i.e. last two rows in table; increasing hydrogen peroxide concentration does not decrease the time taken, therefore, the maximum reaction rate has been reached. The question says that the student gives the maximum reaction rate 1.0 arbitrary unit. So, there are now two ways to look at it. 1) you know that the rate in the last two rows must be 1.0, as this is where the maximum rate is. So, how do you get 1.0? 6/6 or 2) you now know the time for 10 cm3 of oxygen produced is 6s, this is when maximum rate of reaction is reached, so to get the rates for the others you need to see what fraction of 6 (time for maximum rate of reaction) they are.

It's just scaling to give an arbitrary unit.
1
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