How many grams of glucose are needed to prepare 400. mL 0f a 2.0% (m/v) glucose solution?

Question

How many grams of glucose are needed to prepare 400. mL 0f a 2.0% (m/v) glucose solution?
 

800. g

0.0050 g

2.0 g

200. g

8.0 g

Answer 1

This is a conversion question that you can solve via dimensional analysis.

 

You have the following conversion factor:

 

• 2.0% (m/v) glucose solution means: 2.0g glucose/100mL solution. When you see a #% (m/v) it will always imply the conversion factor #g/100mL (m = mass/v = volume) because the term "percent" literally means "per cent", where "cent" means "100"... you have that in English where 1/100 of a dollar is one cent.

 

Now your question is: how many grams of glucose are needed to prepare 400.mL of... solution? Mathematically, this means:

 

?g glucose = 400.mL soln

 

Now apply the conversion factor, and you have:

 

?g glucose = 400.mL soln x (2g glucose/100mL soln)... the "mL solution" cancel out and the only unit left standing is g glucose, which is what you wanted... so you have (400x2/100) g glucose.