Question

An impure sample containing phosphoric acid was completely neutralized with strong base. The titration required 90.0M NaOH solution.

calculate the equivanent weight of the acid
how many moles of protons were titrated
how many moles and grams of H3PO4 were titrated

Answer 1

I think we need more info, like V of NaOH

Answer 2

Sorry 90.0ml of 0.222 M NaOH

Answer 3

Have you solved the first problem?

Answer 4

no

Answer 5

Ok, first calculate the moles of NaOH. Then apply it into the equation
\(3NaOH+H_3PO_4\rightarrow Na_3PO_4+3H_2O\)
3 moles 1 moles
n moles ? moles

\(n_{H_3PO_4}=n_{NaOH}\times 1 \div 3\)

Answer 6

how do we get the N values

Answer 7

0.222=x
-----
.09L for moles

Answer 8

moles= 0.0198moles NaOh

Answer 9

could we use the molarity
M= moles/L
0.22=moles/.09

Answer 10

Sorry, inappropriate formula

Answer 11

Yes. That one

Answer 12

And by the way, we are solving #3, sorry

Answer 13

ok

Answer 14

For the first one, \(\Large equivalent~weight =\frac{molar~mass}{numbers~of~H}\)

Answer 15

we are using the molar mass of H3PO4 for that one or NaOH

Answer 16

97.963g H3PO4
-------------
3 for (h3)

Answer 17

\(H_3PO_4\). We can use that formula to any acids.

For bases, we use \(\Large equivalent~ weight=\frac{molar ~mass}{numbers ~of ~OH}\)

Answer 18

=32.654

Answer 19

Correct

Answer 20

okay for the 3rd one we have
0.0198moles NaOh
where do we go from that to get the moles or was that it

Answer 21

we have to relate that using the balanced equation

Answer 22

Yes. Based on the equation, 3 moles of NaOH will react with 1 moles of H3PO4. Then 0.0198 moles of NaOH will react with....

Answer 23

0.0198 moles NaOh 1 mole H3PO4
------------------ X----------------= .0066 moles H3PO4
1 3 moles NaOH

.0066 moles H3PO4 97.963g H3PO4
------------------ x---------------- = .64656 g H3PO4
1 1 mole H3PO4

Answer 24

Exactly. Good job

Answer 25

how do we find the moles of protons

Answer 26

Actually, protons in this problem is \(H^+\). As you know, \(H\) has 1 p and 1 e. When it is \(H^+\), there is 1 p left

Answer 27

All you need to do is to find the moles of \(H^+\)

Answer 28

in NaOH or H3PO4

Answer 29

Only acids produce \(H^+\). Bases produce \(OH^-\)

Answer 30

so we will use the weak acid H3PO4

.0066 moles H3PO4 3 moles H
----------------- x -----------------=.0198
1 1 mole H3PO4

Answer 31

.0198 moles H

Answer 32

Right

Answer 33

Well done

Answer 34

and that equals the number of my protons

Answer 35

or should i take it to grams

Answer 36

The moles of your protons :)

No, the problem asks for the moles of protons, not its mass

Answer 37

oh okay thank you very much for all of your help, its sometimes hard to relate all the knowledge into one problem

Answer 38

You are welcome. And yes, it is