Hello, I need a quick help with final (w/v) % calculation I am not too sure abou

Question

Hello, I need a quick help with final (w/v) % calculation

I am not too sure about this question, the wording seems a little tricky and harder than it seems. So the question is:

You will be adding 1ml (1000microliters) of a 10% (w/v) sugar solution to 9ml of Phenol Red broth base.

What is the final % (w/v) concentration of the sugar in the Phenol Red broth after the addition of the 10% sugar solution?

The way I was thinking of was:

[(1 ml of 10% sugar solution) / (9 ml OF PR broth)] 100 = 11.11 %

or

Is it

[0.1 of the sugar / 10 mL total volume of 1 mL and 900] x 100 = 1 %

Thanks!

Explanation / Answer

Hey its little tricky with words. Your second assumption is right. The initial sugar concentration is 10% (w/v), it means 10g of sugar is there in 1000ml of solution. When you are adding 1 ml of 10 % this sugar solution to 9 ml of another liquid, you are diluting it to 10 times. So, the final concentration would be 10 times less than the initial concentration and the answer is 1 % (w/v).

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