11 Plus Exams Forum

Hi
I need urgent help withindex form problems such as
The mass of a neutron is 1.6725x10-24g electron 9.109x10-28g proton 1.6748x10-24g

An atom of carbon is made up of 6 neutrons 6 protons and 6 electrons

Q1)what is the mass of one at of carbon? IS IT AS SIMPLE AS 75.17 x10-456g

Q2)How many atoms of varbon are there in 1 gram of carbon

Hi Kate,

No I'm afraid you can't just add the indices together like that.

What you need to do is as follows:

1. Firstly, choose a common index factor, 10-24 is the best in this case.

2. Convert all of the elementary particle weights to the same factor 10-24. In this case this just means dividing the Electron numerator by 10,000. Hence 9.109 x 10-28 = 9.109 div 10,000 (x 10-24)=

0.0009109 x 10-24g

3. Then you can add the various particle weight components together:-

3 (a) 6 neutrons = 10.035 x 10-24
3 (b) 6 protons = 10.0488 x 10-24
3 (c) 6 electrons = 0.0054654 x 10-24

Therefore:-

Q1 The mass of one atom of carbon is 20.0892654 x 10-24grams

Q2 To work out who many atoms of carbon there are in 1 g you divide 1 by the answer to Q1 above:-

1 div ( 20.0892654 x 10-24)

which is the same as

(1 x 10+24) div 20.0892654

or (1 x 10+22) div 0.200892654

4.9778 x 10+24

I have to say that these seems remarkably complex for an 11+ question and I think they would certainly need to have a calculator.

This sounds like the sort of question that they only put as a scholarship question at the end of a Independent Schools maths paper.

What area do you live and where did you get the question from?

Hi thanks for your response we are moving to Kent and my daughters tutor set the question for practice for 11 plus

blimey looks like the sort of thing I was doing at O level 30 years ago....

that sort of question would never appear in the Kent 11+. Buy the NFER practice papers to see the types that are set ......... and maybe get a different tutor!

Or are you aiming for an independent school in Kent which sets this type of question?

Good luck!

p.s. is your tutor a thwarted physicist?

Kate3, I have to agree with Unsure. Those sort of questions are outside the scope of 11 plus; perhaps its off the NASA entrance paper!? KenR is obviously a candidate