I need help from someone smart! I have this chemistry problem and just cant get it (#3)

[Emily Violet]

Hi my name is Sarah iv been stuck on this question for two days, if you could help my it would be amazing 😃

Chromium (II) sulfate is a reagent that has been used in certain applications to help reduce carbon-carbon double bonds to carbon-carbon single bonds. The reagent can be produced by the reaction of zinc, potassium dichromate and sulfuric acid and the other products are zinc sulfate, potassium sulfate and water. a) What is the maximum number of grams of chromium (II) sulfate that can be produced by a reaction mixture containing 3.2 moles of zinc, 1.7 moles of potassium dichromate and 5.0 moles of sulfuric acid?

 

this is the equation  i got hopefully its right. 😐 I just don't know what to do after this part. 

4Zn +K2Cr2O7+7H2SO4=4ZnSO4+2CrSO4+K2SO4+7H2O

[studiot]

Hello Sarah, Emily Violet.

When using mathematics in any sort of technical equation it is really useful to be able to say to yourself in plain words what the equation says in symbols.

Now your proposed equation in symbols says

4 moles of zinc plus 1 mole of potassium dichromate plus reacts with 7 moles of sulphuric acid to produce 4 moles of zinc sulphate plus 2 moles of chromium plus 1 mole of potassium sulphate  plus 7 moles of water.

 

This proposed equation does indeed balance.

It forms your master recipe.

So the first thing to do is to calculate how much of each sulphate is produce by 1 mole of sulphuric acid.

That is the equation right through by 7

4/7 moles of zinc plus 1/7 mole of potassium dichromate plus reacts with 7/7 moles of sulphuric acid to produce 4/7 moles of zinc sulphate plus 2/7 moles of chromium sulphate plus 1/7  moles of potassium sulphate plus 7/7 moles of water.

Keep these as fractions for the moment.

Now fill in the quantities for 4 moles of sulphuric acid

That is multiply the equation right through by 4

4*4/7 moles of zinc plus 4*1/7 mole of potassium dichromate plus reacts with 4*7/7 moles of sulphuric acid to produce 4*4/7 moles of zinc sulphate plus 4*2/7 moles of chromium sulphate plus 4*1/7  moles of potassium sulphate plus 4*7/7 moles of water.

You can now ignore the fractions you don't need and work out how much chromium2 sulphate you can get.

What do you think will happen to the other reagents, are they in excess?

 

Edited February 21, 2020 by studiot

[studiot]

I see you have now used up your 5 posts in the first 24 hours limit.

Hopefully you have enough info to complete this and your other similar questions.

Come back tomorrow and say how you got on.

[Sensei]

Studiot is such a nice person. Helpful and so kind for everybody. Sarah. Don't forget to award him with upvotes. 

 

[Curious layman]

1 hour ago, Sensei said:

Studiot is such a nice person. Helpful and so kind for everybody. Sarah. Don't forget to award him with upvotes. 

 

He's not the only one... +1 🙂