Question

Help with all questions please

Answer all questions on a separate sheet of paper. Show all work and answer all questions completely. Make sure you use the proper number of significant figures and units. Place a box around all answers. 1. (2 points) How many milligrams of potassium dichromate heptahydrate are needed to prepare 50 mL of a 0.0375 M aqueous solution? Describe the procedure for making this solution. 2. (3 points) If 0.125 L of aqueous solution with a density of 0.810 g/mL contains 13.7 ML of CH3CH2OH (ethanol), express the concentration of ethanol in ppm, ppb, molarity, molality, and vol%. Pure ethanol has a density of 0.789 g/mL. 3. (3 points) 35.00 mL of 0.25 M copper (II) nitrate is mixed with 27.25 mL of 0.325 M aluminum (III) carbonate resulting in a copper (II) carbonate precipitate. Write a balanced chemical reaction, determine the limiting reagent and calculate the grams and moles of the precipitate. 4. (4 points) Define the following terms: a. Brønsted-Lowry Acid b. Strong Acid (list the 6) c. Weak acid d. Acid Ionization Constant (write a sample reaction and the expression) e. Brønsted-Lowry Base f. Strong Base (give 4 examples) g. Weak base h. Base Hydrolysis Constant (write the expression) 5. (2 points) Calculate hydronium ion and hydroxide ion concentration of a solution that is pH = 13.42. Is this solution acidic or basic and why?

Answer 1

1. Given

Molarity of Potassium Dichromate Heptahydrate solution = 0.0375M

Volume of Solution = 50 ml

Molecular Weight Potassium Dichromate Heptahydrate = 294.18 gms

Weight of Potassium Dichromate Heptahydrate require = ?

From Molarity definition

Molarity =( Wt/ MolWt ) * (1000/ V in ml)

So 0.0375 =( wt/ 294.18 )* (1000/50)

Wt = (0.0375*294.18)/20

     = 0.55gm

= 550 mg