mass/moles question??

My guess is that such a simple question was turned into such a long paragraph and people got bored before they could be bothered to try to reply.

Your explanation of how your attempted the problem makes no sense.

First calculate the number of mol of KOH = 5.61 / 56.1 = 0.1 mol
THEN apply the 3:1 ratio, n(K3PO4) = 0.1 / 3 = 0.0333 mol
THEN calculate the mass, m(K3PO4) = 0.0333 x 212.3 = 7.08 g.

My guess is that such a simple question was turned into such a long paragraph and people got bored before they could be bothered to try to reply.

Your explanation of how your attempted the problem makes no sense.

First calculate the number of mol of KOH = 5.61 / 56.1 = 0.1 mol
THEN apply the 3:1 ratio, n(K3PO4) = 0.1 / 3 = 0.0333 mol
THEN calculate the mass, m(K3PO4) = 0.0333 x 212.3 = 7.08 g.

hiya i had an exam recently and we've been given back the paper to correct ourselves and i got the below question wrong. i've attempted it again and i just wanted to check if the answer's correct

another student neutralises phosphoric acid with potassium hydroxide solution.

H₃PO₄ + 3KOH -> K₃PO₄ + 3H₂0

H₃PO₄ - phosphoric acid
3KOH - potassium hydroxide
K₃PO₄ - potassium phosphate

and you know what H₂0 is

calculate the mass of potassium phosphate that can be made from 5.61g of potassium hydroxide.
give your answers to three significant figures


anyway i somehow got 98.9g in the exam which obviously wasn't correct

so i noted that 3 moles of potassium hydroxide makes 1 moles of potassium phosphate
mr of potassium hydroxide is 56.1g
however as the question says 5.61g i did the ratio 3:1
but divided 3 by 10, as 56.1 / 10 = 5.61
that means i divided 1 by 10 to also get 0.1
so 0.3 moles makes 0.1 moles

mass = moles x mr [for potassium phosphate]
0.1 x ((39.1 x 3) + (31) + (16 x 4)) = 21.23g

i then put my final answer as 21.2g. however this topic isn't my strongest and i feel like i've done the ratios wrong- so i'm just wondering if my answer was correct.

My guess is that such a simple question was turned into such a long paragraph and people got bored before they could be bothered to try to reply.

Your explanation of how your attempted the problem makes no sense.

First calculate the number of mol of KOH = 5.61 / 56.1 = 0.1 mol
THEN apply the 3:1 ratio, n(K3PO4) = 0.1 / 3 = 0.0333 mol
THEN calculate the mass, m(K3PO4) = 0.0333 x 212.3 = 7.08 g.

i'm confused about the ratio bit though- why 0.1 / 3?

Using the ratio you provided:

H₃PO₄ + 3KOH -> K₃PO₄ + 3H₂0

that means 1 mol of H3PO4 reacts to form 3 mol of KOH.

That means 10 mol of H3PO4 reacts to form 30 mol of K3PO4

That means x mol of H3PO4 reacts to form 3x mol of K3PO4.

That means x/3 mol of H3PO4 reacts to form x mol of K3 PO4.