Question

How many grams of potassium nitrate (KNO3) would form if 2.25 liters of a 1.50 molar lead nitrate Pb(NO3)2 solution reacts with 1.15 liters of a 2.75 molar potassium chromate K2CrO4 solution?

Answer 1

1. write a balanced equation

2. find how many moles of each reactant you have, determine which is the limiting reagent. For this prob, use:

Molarity=moles/L of solution

3. find how many moles you can produced based on the limiting reagent using the stoichiometric coefficients

4. convert moles to mass

moles=mass/molar mass

Answer 2

Thanks so much for your help, I had to ask because I could not solve or answer this question, any chance you have time to walk me through it real quick?

Answer 3

sure, have you balanced it?

Answer 4

Pb(NO3)2 + K2CrO4 --> PbCrO4 + 2KNO3
this is unbalanced correct?

Answer 5

yeah it's good

Answer 6

ok so that is balanced?

Answer 7

yep

Answer 8

alrighty, so finding the moles, I'm not sure which ones I need to find?

Answer 9

find both of the reactants which ever has less is the limiting reactant

Answer 10

is this example since both of reactants have a coefficient of 1, you don't need to worry about the stoichiometry for this step (2).

but if you had say, 2A + 3B -> C, you would have to divide each moles by it's coefficient

Answer 11

hmm I seen to be stuck on this step because I am lost, Pb(NO3)2 + K2CrO4, is Pb(NO3)2 the limiting?

Answer 12

you have to find the moles present of each to find the limiting

since they give you molarity and volume, use:

Molarity=moles/L of solution

Answer 13

Ok well thank you so much for your help but I do not know how to do this and it is unreasonable to ask more of you. Thanks, have a good day!

Answer 14

ill show you how to do one, it's not that hard

so for Pb(NO3)2, you have 2.25 liters of a 1.50 molar

Molarity = moles/L of solution

1.5 M = moles/2.25 L

moles= 1.5M (2.25L) = 3.375 moles

do the same for the other and see which one has less moles

Answer 15

ok so 2.75 M = moles/1.15 L
2.75M (1.15 L) = 3.1625 moles
So K2CrO4 is the limiting because it has less moles?

Answer 16

K2CrO4 = 3.1625 moles
Pb(NO3)2 = 3.375 moles

Answer 17

yeah, so now that you know the limiting reactant, you have to relate it to the product

this time you have to use the coefficients like this:

A + B -> 2C

\[\frac{ B }{1 }=\frac{ C }{ 2 }\]

then isolate the one you don't know

Answer 18

just try it, il tell you if it's wrong

Answer 19

I'm not sure how to start off, like the set up?

Answer 20

am I adding the two moles together?

Answer 21

moles of species one/its coefficient=moles of species two/its coeffcient

Answer 22

you're solving for the unknown KNO3