Question

Goal #2: Determine the aqueous concentration of IO3- in each sample by titration.

Molarity	Formula	Name	Quantity
Determined in Part I	Na2S2O3(aq)	Sodium Thiosulfate	250 mL
	KI(s)	Potassium Iodide	10 scoops using the spoon provided in your kit
1.0 M	HCl	Hydrochloric Acid	25 mL
0.20%		Starch Solution	10 mL

Fill the buret with the thiosulfate titrant. Drain some titrant out until the level is a milliliter or so below 0.0 mL. Make sure you don't have a bubble at the bottom stem of the buret (below the stopcock).

Carefully pipet 10.00 mL of your solution “A1” into a clean 250 mL Erlenmeyer flask.

Add 10 - 20 mL of deionized water.

Add 1/4 teaspoon (1 scoop using the white spoon provided in kit) of solid KI.

Add 3 ml of 1 M HCL. Swirl to mix. The solution should be a dark yellow-brown color.

QUESTION : Describe how you would make the three calcium solutions (solutions A, B, and C). Include glassware.

Answer 1

QUESTION : Describe how you would make the three calcium solutions (solutions A, B, and C). Include glassware.

Answer:

We know that molarity = Moles of solute / Volume of solution in litres

So if we wish to preapare 1M solution of Calcium then we need a salt of calcium.

Let us take CaCl2 as salt.

The molecular weight of CaCl2 = 111 g / mL

To make 500mL of 1M CaCl2 solution.

1) we will weight 111/2 grams of CaCl2 on watch glass.

2) we will then take a 500mL of volumetric flask and will pour the salt in it.

3) Then will dissolve the salt in minimum amount of distilled water

4) Will make up the volume of volumetic flask with water upto the mark of flask.

5) we may use funnel for pouring of water in flask.

B) we can further dilute the 1M solution to any concentration

(i) 0.5 M , 500mL

We will take 250 mL of the above made solution and will fill it in 500mL of volumetric flask and will make up the solution to 500mL with distilled water.

(ii) 0.1 M , 500mL

We will take 50mL of above (1M) solution and will fill it in 500mL volumetric flask and will make up the solution to 500mL with distilled water.