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chemistry question - potassium dichromate

As.1997

Please have a look at the attachment.

The answer is C 26g.
I had a look at the explanation for the answer and it said you do 80-54 =26
I understand how you get the 80 and 54 but I am not sure as to why we would take them away?
Is this because you have 80g of solute dissolved at 70 degrees celcius so no crystals will form, but at 20degrees celcius only 54 grams will remain dissolved, leaving the extra 26grams to form crystals?

(edited 4 years ago)

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Reply 1

Fran2311

It gives the mass of the water lost as it cools and therefore the mass of crystals formed

Reply 2

As.1997

Original post by Fran2311

It gives the mass of the water lost as it cools and therefore the mass of crystals formed

Hi, thank you for your response. I'm still a little lost with the water aspect. How does this relate to crystal formation?

Reply 3

Fran2311

Original post by As.1997

Hi, thank you for your response. I'm still a little lost with the water aspect. How does this relate to crystal formation?

80 is the mass of the hydrous crystals (crystals dissolved in water). You’re told that at 54 degrees, some crystals will form. As the mixture has cooled, some water will be lost as the crystals form. 80-54 gives the mass of crystals as 80 and 54 are the masses of water present in each sample of crystals.

Reply 4

As.1997

I’m not too sure if 80 and 50 represent the masses of water. I think they represent the masses of potassium chlorate .

(I promise I’m not trying to be annoying on purpose — I’m just confuzzled)

(edited 4 years ago)

Reply 5

Fran2311

Original post by As.1997

No don't worry it's okay. Chemistry is hard. Yes you are correct. They are the masses of potassium chlorate with the water. Therefore taking them away gives the mass of crystals formed