What are the different types of JC Chemistry tuition classes available at your centre?

We have 3 modes of learning for students to choose from: weekly physical classes at Bishan; weekly online lessons via Zoom; and on-demand video lessons.

Are you the only Chemistry tutor conducting the classes or do you engage other tutors to do that?

Please be rest assured that I conduct all my classes personally and I do not engage other tutors to teach at my centre.

How well do your students perform after attending your H2 Chemistry tuition classes?

Most of my students showed improvements by at least 3 grades and more than 80% have attained distinction for A Levels. The earlier the students join my classes, the more confident I am in improving their grades.

What is your class size at Bishan?

Usually the class size is around 10 to 12 students. Max class size is 16 pax.

Is there makeup lesson if I miss a class?

Yes makeup lesson is available in the same week subject to availability. If makeup class is not possible, the student can view the recorded video lessons at Google Classroom.

Do you have trial lesson available? How much is it?

Yes we do. Fees for trial lesson are for Bishan class and for Zoom online class.

Does your centre offer O Level chemistry tuition? Do you teach IB / IP chemistry tuition? How about H1 Chemistry?

Chemistry Guru specialises in H2 Chemistry for JC1 and JC2 or IP Year 5 and IP Year 6 students only. Find out all the information about A Level H2 Chemistry and the detailed comparison between H1 and H2 Chemistry. We do not conduct lessons for H1 Chemistry, O Level Chemistry, IB Chemistry or IP Chemistry at IP Year 3 and IP Year 4.

Pseudo First Order Reactions - Kinetics

In this video we want to discuss the concept of Pseudo first order reaction in Kinetics.

Let Chemistry Guru, Singapore's top JC Chemistry tuition centre, guide you through an example:

Given a reaction is first order with respect to both reactants A and B.

For an experiment, where [A] = 0.01 moldm^-3 and [B] = 0.50 moldm^-3, the half life was determined to be 10 minutes.

What is the new half life when the concentration of B is changed to 1.00 moldm^-3?

1. Determine rate equation

Let's first write down the rate equation based on the order of the reaction with respect to A and B.

Since order is 1 with respect to both reactants then the rate equation is given as:

rate = k [A][B]

The overall order of the reaction is 2, which makes it difficult for us to determine half life as we know that half life is not constant for overall order 2 reaction.

In fact, in A Level Chemistry syllabus we are only required to find half life for first order reactions.

This means that the question is hinting to us that in order for us to determine half life for a second order reaction, we need to change this reaction into a first order reaction.

That's where the concept of pseudo first order reaction comes in.

2. Criteria for Pseudo First Order Reaction

Once we suspect the question is about pseudo first order reaction we can verify this by looking out for one of these criteria:

a. excess reactant - the concentration of excess reactant is treated as constant since the change in the amount of excess reactant is negligible as the reaction proceeds.

b. catalyst - the concentration of catalyst is constant as it is chemically unchanged at the end of the reaction.

For this question we notice that the concentration of B is 50 times more than concentration of A.

So we can treat the concentration of B as constant and make it part of rate constant k.

pseudo first order reaction rate equation

So what we have effectively done is to change an overall order 2 reaction and make it appear like an order 1 reaction.

Hence the name "pseudo first order reaction".

3. Determine Half Life

Since now the reaction is first order, half life is a constant and we can write it in terms of the original rate constant k and concentration of B.

pseudo first order reaction half life

From the expression we know that half life is inversely proportionate to concentration of B.

Comparing the 2 experiments, when we double the concentration of B from 0.5 moldm^-3 to 1.0 moldm^-3, we will expect the half life to be halved from 10 minutes to 5 minutes.

pseudo first order reaction compare experiment