Question

Calculate how to make 0.5 L of 6 M HCl.

Answer 1

Hydrochloric acid (HCl) has a mplecular weight (molar mass) of 36.46 g/mol .

Hence dissolving 36.46 grams of HCl (solute) in 1000 ml (1 litre ) of water (which is the solvent), would yield us a 1 Molar solution of HCl.

Here we need to calculate how many grams of HCl is needed to be dissolved in 500 ml (0.5 litres) to obtain a solution that is of 6 molar concentration.

Using direct proportion formula,

Solvent solute-grams to be dissolved molarity

1000ml 36.46 gms 1M final solution

500ml x gms 6M final solution

We need to find x,

hence x would be

= (500/1000) * (6/1)* 36.46

= 109.38 grams to be dissolved in 500ml of water to obtain 6M HCl solution.

Please refer to the following links for calculation and mathematical aids:

https://www.mathsisfun.com/algebra/directly-inversely-proportional.html

http://ncert.nic.in/ncerts/l/heep210.pdf

You can use thi free online tool from Prism website to readily carry out such operations and calcultions:

https://www.graphpad.com/quickcalcs/Molarityform.cfm

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