Water hardness 2

Question 1

What is Total Hardness measured as?

Answer 1

mg/L of CaCO3

Question 2

What is the formula for calculating Total Hardness as CaCO3 using calcium and magnesium concentrations?

Answer 2

Total Hardness as CaCO3 = (2.5 x Ca2+) + (4.12 x Mg2+)

Question 3

Calculate Total Hardness as CaCO3 given Ca2+ = 25 mg/L and Mg2+ = 8 mg/L.

Answer 3

95.5 mg/L

Question 4

How can calcium hardness be determined?

Answer 4

By titrating 100 mL of water with a 0.02M solution of EDTA, buffered with NaOH.

Question 5

What is the equivalence of 1 mL of EDTA solution in terms of calcium?

Answer 5

1 mg of calcium

Question 6

How is magnesium hardness calculated?

Answer 6

Magnesium hardness = Total hardness - Calcium hardness

Question 7

What is the classification of water hardness for 0-37.5 mg/L CaCO3?

Answer 7

Very soft

Question 8

What classification corresponds to 37.5-87.5 mg/L CaCO3?

Answer 8

Soft

Question 9

Define the classification for water hardness at 87.5-175 mg/L CaCO3.

Answer 9

Medium hard

Question 10

What classification is given for 175-375 mg/L CaCO3?

Answer 10

Hard

Question 11

What is the classification for water hardness greater than 375 mg/L CaCO3?

Answer 11

Very hard

Question 12

What is the sodium concentration in Melbourne in mg/L?

Answer 12

4.5

Question 13

What is the calcium concentration in Burton in mg/L?

Answer 13

268

Question 14

Fill in the blank: The total dissolved solids in Munich are ______ mg/L.

Answer 14

273

Question 15

True or False: The chloride concentration in Dublin is higher than in London.

Answer 15

True

Question 16

What is the magnesium concentration in Pilsen in mg/L?

Answer 16

1

Question 17

List the classification of water hardness for the following locations: Burton, London, Dublin.

Answer 17

• Burton: Hard
• London: Soft
• Dublin: Soft