Question

PLEASE SHOW WORK! Answers are included.

What is the molarity of a 20% by weight solution of NaOH? MW=39.99

A: 5M

What percentage (%) is 1.5M NaOH?

A: 6%

How would you prepare 250 mL of a 0.5M NaCl solution? MW=58.44

A: 7.31g NaCl and H2O until reach 250 mL

If you add 10g of NaCl to 500 mL, what is the concentration, in percent, of the solution?

A: 2% NaCl solution

If you add 10g of NaCl to make a 3M solution, what is the total volume? MW=58.44

A: 57 mL NaCl solution

Given 30% NaOH solution, how many mL’s of solution would you use to prepare 300 mL of 10% solution?

A: 100 mL NaOH

If you use 10 mL of a 25% NaOH solution to dilute to a final volume of 100 mL, what is the final concentration?

2.5% NaOH solution

If you use 10 mL of stock NaCl solution to make 20 mL of 0.3M NaCl solution, what is the concentration of the stock solution?

A: 0.6M

Answer 1

Solution: 1. 20% w/v solution will consists of 20 g of sodium hydroxide for every 100 mL of solution. 1000mL solutionx (20 g NaOH/100mL solution) 200 g NaOH Sodium hydroxide's molar mass 40 grams 200g.(1 mole/40.0g) 5.0 moles NaOH Since the sample volume 1L, its molarity will be C-nV, C 5.0 molesx 1 L C 5 M 2. For the given question X%-X grams in 100ml X grams molarity/Lx Molecular weight of NaOH -1.5mole/1000ml x 40-60 grams /1000ml-6 grams/100ml Thus X 6 And the percent-696 3. We will determine NaCL quantity in 250 ml solution 0.5 moles/1000 ml Number of moles in 250 mに(0.5/1000) x 250 = 0.125 mole Weight of 0.125 moles of NaC 0.125 x58.44 grams 7.305 grams of Nacl- 7.31 grams of Nacl and th rest will be water The X % = X grams in 100 ml Thus 10g/500ml of Nacl concentration if divided by 5 both in numerator and denominator will give (10g/5)4500/5ml = 2grams in 100 ml Thus the percent concentration 2 % 4.