Tips & Tricks - Tip # 6 - Go Step-By-Step While Solving Numerical Problems

Hello Students. Welcome to Mystery In Chemistry’s Tips & Tricks series. Understanding chemistry and scoring high in exams are two different things and hence require different set of skills. Let us learn the next tip to help you score 100/100 in chemistry.

So here is the 6th tip - Go step-by-step while solving numerical problems.

Here is a 3 marks numerical problem. 

The decomposition of NH3 on platinum surface is zero order reaction. If rate constant (k) is 4 x 10–3 Ms–1, how long will it take to reduce the initial concentration of NH3 from 0.1 M to 0.064 M.                       (3 Marks)

You may recall from our previously discussed formula that you should not take more than 7 minutes for a 3 marks question.

Very often students know the answer but do silly mistake while omitting few steps. 

Always go step-by-step. Because you are getting marks not only for the correct answer but also for each step.

 

First step - Write the formula and you have your 1 mark. t =  [A0]− [A] / k  ...... When t is reaction time, [A0] is initial concentration, [A]  is final concentration and k is rate constant. Check the things already given in the question with units.  [A0] = 0.1 M, [A] = 0.064 M, k  = 4 x 10−3 Ms−1

Next, do the second step i.e. Substitute all the values in the formula. For this step you are getting another 1 mark. 

In third step - Do the calculation and get the correct answer. Finally write the answer clearly along with the units. And secure your last mark too. 

So, it is quite clear that going step-by-step is not only easy and clear, but less time consuming. Moreover you are getting marks for each step. 

Please note that even if you write the correct answer but without the steps - you get only 1 mark.

So always solve numerical problems step-by-step.

Thank you.