Click to Continue

For the next question, click on the Next Question button.

Question 1 of 3

How many moles of Sodium Hydroxide are there in a 0.7500 molal aqueous solution of Sodium Hydroxide if the solution contains 25 grams of water? Answer to 5 decimal places.

Type in your answer and PRESS ENTER

moles
0.01875 moles of Sodium Hydroxide are present.

Number of Moles of Component = Molality x Mass of Solvent (in kgs)

Convert mass of water from grams to kilograms: 25 g = 0.025 kg

Moles of Sodium Hydroxide = 0.7500 x 0.025 moles
Moles of Sodium Hydroxide = 0.018750 moles
Moles of Sodium Hydroxide = 0.01875 moles to 5 dec pl

No, that is not the correct answer.

Have another go: just type in your new answer and press Enter.
If you continue to have problems, have a look at the answer.

For the next question, click on the Next Question button.

Question 2 of 3

How many grams of Potassium Chloride (RMM 74.56) would you need to weigh in order to prepare a solution containing 0.2450 molal Potassium Chloride and 750 grams of water? Answer to 2 decimal places.

Type in your answer and PRESS ENTER.
grams
You would need to weigh 13.70 grams of Potassium Chloride.

Number of Moles of Component = Molality x Mass of Solvent (in kgs)

  1. Find the number of moles of Potassium Chloride needed.
    Convert mass of water from grams to kilograms: 750 g = 0.75 kg
    Moles of Potassium Hydroxide = 0.2450 x 0.75 moles
    Moles of Potassium Hydroxide = 0.18375 moles
  2. Find the mass of Potassium Chloride needed.
    Mass = Moles x RMM = 0.18375 x 74.56 g = 13.700 g
    Mass = 13.70 g to 2 dec pl

No, that is not the correct answer.

Have another go: just type in your new answer and press Enter.
If you continue to have problems, have a look at the answer.

For the next question, click on the Next Question button.

Question 3 of 3

You need to prepare a 1.500 molal aqueous solution of Sodium Bicarbonate (NaHCO3). You have 150 grams of water; how many grams of Sodium Bicarbonate would you weigh out? Answer to 3 significant figures.

Type in your answer and PRESS ENTER
grams
You would need to weigh 18.9 grams of Sodium Bicarbonate.

Number of Moles of Component = Molality x Mass of Solvent (in kgs)

  1. Find the number of moles of Sodium Bicarbonate needed.
    Convert mass of water from grams to kilograms: 150 g = 0.15 kg
    Moles of Sodium Bicarbonate = 1.500 x 0.15 moles
    Moles of Sodium Bicarbonate = 0.225 moles
  2. Find the mass of Sodium Bicarbonate needed. (RMM NaHCO3 = 84.0)
    Mass = Moles x RMM = 0.225 x 84.0 g = 18.90 g
    Mass = 18.9 g to 3 sig figs

No, that is not the correct answer.

Have another go: just type in your new answer and press Enter.
If you continue to have problems, have a look at the answer.