4. If 6.7 g of sodium acetate or 6.7 g of magnesium acetate is dissolved in a to

Question

4. If 6.7 g of sodium acetate or 6.7 g of magnesium acetate is dissolved in a total volume of 0.200 L of water calculate
a) the molarity of sodium acetate
b) the molarity of magnesium acetate
c) the molarity of acetate ion in each solution

5. How many grams of EDTA tetrahydrate are needed to prepare 500 mL of a 0.010 M solution?

6. a) How would you prepare 100 mL of a 0.040 M solution of acetate ion using sodium acetate?
b) Using magnesium acetate?

*Must be answered as stated above and all work must be shown to get any points!!!

Explanation / Answer

4)

A)6.7 g sodium acetate in 0.200L or 200 mL water

MW of sodium acetate=82

82 g is 1 mole

6.7 is =6.7/82=0.081 mole

so 0.081 mole in 200 ml

In 1000 ml=0.081X5=0.405 molar

B)6.7 g Magnesium acetatein 200 mL

MW of magnesium acetate=142.4

no of moles=6.7/142.4=0.047 mole

Molarity=0.047X5=0.235 molar

C) For 1 mole sodium acetate contain 1 mole acetate ion

So molarity of acetate ion in sodium acetate solution=0.405 molar

For 1 mole magnesium acetate contain 2 mole acetate ion

So molarity of acetate ion in magnesium acetate solution=0.235 X 2=0.47 molar

5)MW of EDTA tetra sodium tetrahydrate=452.2g

For 1 molar,452.2 g in 1L

For 0.010M=452.2gX0.010=4.522g in 1l

for 500mL=4.522/2=2.261g

6)100ml 0.04M acetate ion

(i)Using Sodium acetate

AS 1 mole gives 1 mole acetate ion therefore 0.04M sod.acetate solution required

So (82X0.04)/10=0.328g

(Ii)Using Magnesium acetate

AS it gives 2 mole so Magn.acetate solution of 0.02 M

So (142.4X0.02)/10=0.284g

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