Question

What is the pH of the solution prepared by allowing 2.75 g of Na2O to react with 550.0 mL of water? Assume that there is no volume change.

Answer 1

Na2O(aq)+H2O(l)→2NaOH(aq)

Answer 2

@Hoslos

Answer 3

@Cuanchi

Answer 4

just find the molarity of [OH^{-} ] in NaOH
and then take its negative log with base=10

Answer 5

im still not getting the right answer... so i found M=.000161342. then i take the negative log of that? @imqwerty

Answer 6

ok :) ima tell it step wise

Answer 7

1st of all can u calculate the number of moles of NaOH that will be formed?

Answer 8

yes i did that

Answer 9

whats the value u got?

Answer 10

.088738303

Answer 11

yes correct :)
can u tell this-> how many moles of (OH) are present in 0.0887 moles of NaOH?

Answer 12

ohhh thats what i didnt do. there are 2

Answer 13

there are 2??
what do u mean?

Answer 14

wait nvm.. read that wrong.. wouldnt it just be the same?

Answer 15

yes the moles will be the same :)

Answer 16

next step is to calculate the molarity of OH

Answer 17

i got .000161342 for that

Answer 18

yeah this is where u made the mistake
when we calculate molarity we take the volume in litres but what we have is 550ml
convert it into litres and then calculate :)

Answer 19

it says assume there is no volume change

Answer 20

so wouldnt i keep it in mL?

Answer 21

yes there is no volume change it means the volume is constant :)

ok lemme give u an example :)
can u write 1000grams as 1kilogram?

Answer 22

1000 grams is 1 kilogram

Answer 23

like this
1000ml=1Liter

^both are same

so how many liters are equal to 550ml??

Answer 24

.55 L

Answer 25

yes :)
we changed the volume from ml to L cuz we use litres to find out molarity
so calculate the molarity now

Answer 26

so now M= .16134236

Answer 27

yes :)

now u have the molarity
we can calculate pOH

\[p^{OH}=-\log[OH]\]

after calculating pOH
we use this equation to get our pH-\[p^{H}+p^{OH}=14\]

substitute pOH that u get in this eq to get pH

Answer 28

here [OH] represents the concentration(molarity of OH)

Answer 29

ok so i got pH= 13.208

Answer 30

yea correct :)

Answer 31

awesome!! thank you so much!! :)

Answer 32

np B) yw (: