A chemist must prepare 800ml of potassium hydroxide solution with a pH 13 of at 25. He will do this in three steps:

Fill a volumetric flask about halfway with distilled water.
Weigh out a small amount of solid potassium hydroxide and add it to the flask.
Fill the flask to the mark with distilled water.

Calculate the mass of potassium hydroxide that the chemist must weigh out in the second step. Round your answer to significant digits.

4.48 grams of potassium hydroxide that the chemist must be weighing out.

Explanation:

The pH of the KOH solution = 13

pH + pOH = 14

pOH = 14 - pH = 14 - 13 = 1

1 mole of hydroxide ions are obtained from 1 mole of KOH. Then 0.1 mole of hydroxide ions will be obtained from :

of KOH

Volume of KOH solution = 800 mL = 0.800 L ( 1 mL = 0.001 L)

Moles of KOH = 0.1 M × 0.800 L = 0.08 mol

Mass of 0.08 moles of KOH :

0.08 mol × 56 g/mol = 4.48 g

4.48 grams of potassium hydroxide that the chemist must be weighing out.

calculate how many grams of ammonia can be produced from 4.21 grams of

n2 + 3h2 = 2nh3

my answer:

25.0g n2 x (1 mol/ 28.0gn2) x (2 mol nh3/ 1 mol n2) x (17.0g nh3/ 1 molnh3) = 30.36g n2

25.0g h2 x (1 mol h2/ 2.00g h2) x (2 mol nh3/ 3 mol h2) x (17.0g nh3/ 1 mol nh3) = 141.67g h2

lr = n2

it would be d. henry moseley

hope this !

and sorry if i'm late. have a good rest of your day! : d