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# 'from the mass of CaCO3, calculate the molarity of of CaCO3 Solution and also in mg/l watch

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1. Need help with this. First lab of uni but so lost because they use units and wording ive never used before (ml,molarity). Im used to using cm3/dm3/moldm-3.

Context:
Weigh out accurately (4 decimal places) about 0.25g of calcium carbonate (Mol. wt. 100.09g) into a clean dry beaker. Carefully add dropwise about 2ml of dilute hydrochloric acid to dissolve the solid. The solid must all be dissolved (check after the fizzing has stopped). The clear solution can then be transferred by washing with distilled water into a 250ml volumetric flask and the solution made up accurately to 250ml. Part B

The question 'from the mass of CaCO3, calculate the molarity of of CaCO3 Solution and also in mg per litre'

My CaCO3 is 0.2555g

The answer is somehow 0.0102moldm-3 (M?)
and 25.53mgl-1.

Could someone go through it?
2. (Original post by valbrechts)
Need help with this. First lab of uni but so lost because they use units and wording ive never used before (ml,molarity). Im used to using cm3/dm3/moldm-3.

Context:
Weigh out accurately (4 decimal places) about 0.25g of calcium carbonate (Mol. wt. 100.09g) into a clean dry beaker. Carefully add dropwise about 2ml of dilute hydrochloric acid to dissolve the solid. The solid must all be dissolved (check after the fizzing has stopped). The clear solution can then be transferred by washing with distilled water into a 250ml volumetric flask and the solution made up accurately to 250ml. Part B

The question 'from the mass of CaCO3, calculate the molarity of of CaCO3 Solution and also in mg per litre'

My CaCO3 is 0.2555g

The answer is somehow 0.0102moldm-3 (M?)
and 25.53mgl-1.

Could someone go through it?
The units you haven't seen before:
ml is millilitres. Maybe you are used to using cm3 / cubic centimetres instead, this is the same volume. Either way it is 0.001dm3 (or 0.001L).
ml is more correctly written mL.

Molarity is just moles per dm3 of solution.

You no longer have calcium carbonate in solution, as you neutralised it completely with the acid. Is it concentration of calcium that you are being asked for?
3. (Original post by TutorsChemistry)
Is it concentration of calcium chloride? that you are being asked for?
Did you forget something?
4. Moles= mass/Mr
ml=cm3
cm3x10-3=dm3
Concentration= moles x volume

I don’t have a calculator but that’s the working

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Updated: October 15, 2017
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