April 11, 2021, 06:40:15 AM
Forum Rules: Read This Before Posting

### Topic: pH value of NaCl+HCl  (Read 218 times)

0 Members and 1 Guest are viewing this topic.

#### mglbs

• New Member
• Posts: 7
• Mole Snacks: +0/-0
##### pH value of NaCl+HCl
« on: February 23, 2021, 07:35:06 AM »
How can I calculate the pH value if I add 30g NaCl in 20ml HCl with 0.2 mol/L?

I tried to calculate it and got a pH of 1.4 is it right? Can NaCl effect the pH?

#### AWK

• Retired Staff
• Sr. Member
• Posts: 7984
• Mole Snacks: +555/-93
• Gender:
##### Re: pH value of NaCl+HCl
« Reply #1 on: February 23, 2021, 09:02:13 AM »
About 5 g of NaCl will be dissolved in 20 ml of 0.2 M HCl. Sodium chloride lowers the pH of hydrochloric acid a little, but this is difficult to calculate.
AWK

#### mglbs

• New Member
• Posts: 7
• Mole Snacks: +0/-0
##### Re: pH value of NaCl+HCl
« Reply #2 on: February 23, 2021, 09:32:31 AM »
I did it like that

#### AWK

• Retired Staff
• Sr. Member
• Posts: 7984
• Mole Snacks: +555/-93
• Gender:
##### Re: pH value of NaCl+HCl
« Reply #3 on: February 23, 2021, 09:52:21 AM »
Unrecognizable format.
AWK

#### mglbs

• New Member
• Posts: 7
• Mole Snacks: +0/-0
##### Re: pH value of NaCl+HCl
« Reply #4 on: February 23, 2021, 10:35:21 AM »
V(HCl)=0.02L c(HCl)=0.2mol/L

30g NaCl  M= 83 g/mol  n(NaCl) = 0.517 mol

n(HCl)=4⋅10−4 mol

c(H+)= (0.517 mol − 4⋅10-4 mol) / 0.02L = 25.83mol/L

pH=-log(c(H+))=1.4

#### AWK

• Retired Staff
• Sr. Member
• Posts: 7984
• Mole Snacks: +555/-93
• Gender:
##### Re: pH value of NaCl+HCl
« Reply #5 on: February 23, 2021, 10:44:46 AM »
M NaCl = 58.5
NaCl in solutions is nearly neutral.
AWK

#### mglbs

• New Member
• Posts: 7
• Mole Snacks: +0/-0
##### Re: pH value of NaCl+HCl
« Reply #6 on: February 23, 2021, 12:05:49 PM »
So what I did is wrong

#### AWK

• Retired Staff
• Sr. Member
• Posts: 7984
• Mole Snacks: +555/-93
• Gender:
##### Re: pH value of NaCl+HCl
« Reply #7 on: February 23, 2021, 12:20:31 PM »
1. This amount of  NaCl will not dissolve.
2. Formula weight of NaCl is different.
3. If you cannot account for the activity factors for high ionic strengths, just calculate the pH of a pure acid.
AWK