Homework Help Question & Answers

O ACIDS AND BASES Preparing a strong base solution with a given pH A chemist must...


O ACIDS AND BASES Preparing a strong base solution with a given pH A chemist must prepare 800.0 mL of sodium hydroxide soluti
O ACIDS AND BASES Preparing a strong base solution with a given pH A chemist must prepare 800.0 mL of sodium hydroxide solution with a pH of 13.40 at 25°C. She will do this in three steps: • Fill a 800.0 mL volumetric flask about halfway with distilled water. • Weigh out a small amount of solid sodium hydroxide and add it to the flask. • Fill the flask to the mark with distilled water. Calculate the mass of sodium hydroxide that the chemist must weigh out in the second step. Round your answer to 2 significant digits. X 5 ?
0 0
Add a comment
Answer #1

1st find the concentration of NaOH

use:

pH = -log [H+]

13.4 = -log [H+]

[H+] = 3.981*10^-14 M

use:

[OH-] = Kw/[H+]

Kw is dissociation constant of water whose value is 1.0*10^-14 at 25 oC

[OH-] = (1.0*10^-14)/[H+]

[OH-] = (1.0*10^-14)/(3.981*10^-14)

[OH-] = 0.2512 M

So,

[NaOH] = 0.2512 M

volume , V = 8*10^2 mL

= 0.8 L

use:

number of mol,

n = Molarity * Volume

= 0.2512*0.8

= 0.201 mol

Molar mass of NaOH,

MM = 1*MM(Na) + 1*MM(O) + 1*MM(H)

= 1*22.99 + 1*16.0 + 1*1.008

= 39.998 g/mol

use:

mass of NaOH,

m = number of mol * molar mass

= 0.201 mol * 40 g/mol

= 8.038 g

Answer: 8.0 g

Add a comment
Know the answer?
Add Answer to:
O ACIDS AND BASES Preparing a strong base solution with a given pH A chemist must...
Your Answer:

Post as a guest

Your Name:

What's your source?

Earn Coin

Coins can be redeemed for fabulous gifts.

Not the answer you're looking for? Ask your own homework help question. Our experts will answer your question WITHIN MINUTES for Free.
Similar Homework Help Questions
Free Homework App
Download From Google Play
Scan Your Homework
to Get Instant Free Answers
Need Online Homework Help?
Ask a Question
Get Answers For Free
Most questions answered within 3 hours.