Stuck with Pre-Reg exam calculations?

[goldenpharm]

Hi, ive got the answer to the second question it is 378kg i think. but the option is 378g. am i wrong or are the units in the question incorrect?

[DavidS]

Please give your working. We are delighted to help show you where you are going wrong (if we know ), but we don't do answers any more.

In fact, anyone giving answers is likely to have their answer "moderated" slightly, so it can't be just copied!

[johnep]

Any question involving calculation is really testing your knowledge of her to work out the answer, not the actual answer itself. Best marks in an exam are to be gained by deriving an equation from first principles, and then doing a calculation based on the equation. Easy marks if you know how to do it.
johnep

[Fleegle]

Hi, i'm stuck with this question,
Potassium permanganate solution 1 in 8000 is often prepared from a stock solution of ten times this strength. How much potassium permanganate will be needed to make sufficient stock solution if the patient uses 200 ml each day, of the diluted solution 1 in 8000, for 20 days?
Question 4 answers
A. 100g
B. 125g
C. 250g
D. 400g
E. 500g

For some reason the answer i have got is 0.5g. But this aint one of the choices. What does everybody else get?

Thanx in advance

I got 0.5g as well..there must be something wrong with the question. Please post your full working to show how you arrived at this answer. Then, contact your tutor and request he/she contact me directly by personal message on this forum. Please also tell them you requested the answer to the question here.

I will look after the rest, following discussion with your tutor, and post your answer as soon as possible.

Fleegle. (Forum Moderator)

[goldenpharm]

These questions are not from my tutor. they are pre-reg style questions i have obtained from my peers.

Im trying to practice as many calcs as possible in prep for the pre reg exam on 26 june!!

200 x 20 =4000ml of diluted sol
therfore 1g in 8000 mL, so 0.5g in 4000ml.

Refer back to stock sol, 1g in 800 ml, 0.5g in 400ml.

So answer is 0.5g of potassium permang required to make sufficient stock.

[Nik]

Perhaps the units to the options should be in milligrams instead of grams ?

[goldenpharm]

Working out for the second question i asked

420kg = 420,000,000mg
Each tab = 700mg, therefore 420,000,000/700 = 600,000 tablets
600,000 x (active) 600mg = 360,000,000mg of active required

360,000,000/100 x 5 =18,000000 (5% overage)

360,000,000 + 18,000000 = 378,000,000mg

= 378,000g
=378kg

[goldenpharm]

according to my calculations the units in the answers for both questions are wrong. I just wanted confirmation from others.

Im pretty confident with my calcs, but we are all prone to making silly errors.

If anyone has any prereg style questions or past papers/sample papers that they could forward me via email, i would be very grateful.

Thanx

[Nik]

Sample papers are available on the rpsgb site. I got the same answer for your 2nd question, maybe the units you were given are wrong.

[Fleegle]

Fully agree..the answers given aren't even close! I wasn't being funny..there is a problem with the question..

Fleeg.