GPhC Exam Tutoring

Just finished our second Google Hangout for GPhC tutoring. If you would like to join the next one please email us. The main note that came out this session is to familiarize yourself with the "two jugs" method for calculations. Have a look at these pharmacy calculation questions and you will see what I mean...

That you have two solutions.

Solution 1 is 120ml of a 5mg/ml solution.

Solution 2 is 80ml of a 1mg/ml solution.

If I were to pour 20ml of the first solution into the second what is the resulting concentration?

So you are putting 20mg from solution 2 into solution 1. So,solution 3 is going to be 140ml overall.

120 x 5 = 600mg in 120ml.

600mg+20mg=620mg/140ml

140 x 2= 280

140 x 3 = 420

140 x 4 = 560mg

140 x 5 = 700mg

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Solution A contains 0.2%, volume is 30ml.

Solution B contains 3mg/5ml, volume is 150ml.

You need to take 2ml of solution A and place it into solution B to make solution C. What is the new concentration?

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0.2% = 0.2g per 100ml. 

0.2/100x2 = 0.004g

4mg ———> Solution C

What is the new volume?

150 + 2 = 152.

3mg per 5ml. 150/5 x 3 = 90mg

90+4 = 94mg/152ml

94/152 x 100

A. 61.84%

B. 0.06%

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Solution A contains 10mg/ml of Na-Cl and its volume is 100ml.

Solution B contains 0.5% of NaCl and its volume is 20ml.

You place 10ml of solution A into solution B. What is the resulting concentration of Sodium ions in mg/ml?

10ml of solution A contains. 10mg x 10 = 100mg this is placed into solution C which contains. 

0.5g in 100ml. Which is 0.1g in 20ml. 

Resulting solution will be 30ml (Volume of solution C). 

So... 100mg + 100mg in 30ml = 

200mg in 30ml which is 

0.7% = NaCL

35.5 / 55

So… 50% is 0.35%

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