Complexometric titration

What is the main cause of water hardness?

• 
  Sodium and potassium compounds

• Calcium and magnesium compounds

• Iron and copper compounds

• Zinc and lead compounds

What is the effect of scale formation in water heating systems?

• 
  Increases heat transfer efficiency

• Reduces heat transfer efficiency

• Has no effect on heat transfer

• Enhances water flow in pipes

What is the log Kf value for the Ca2+ ion?

• 10.65

• 8.72

• 15.36

• 13.89

What color does Eriochrome black T turn when it binds to a metal ion?

• 
  Blue

• Green

• Red

• Yellow

What is the objective of the experiment described in the document?

• 
  To learn about acid-base titration.

• To determine the calcium and magnesium hardness of a water sample.

• To study the solubility of metal hydroxides.

• To measure the pH of a solution.

What is the purpose of preparing an additional sample for titration?

• 
  To increase the concentration of the solution

• To determine the approximate end point quickly

• To reduce the volume of the solution

• To change the color of the indicator

How should you prepare a pH 10 buffer according to the document?

• 
  Mix 100 mL of water with 10 g of NaOH

• Add 142 mL of 28 wt% aqueous NH3 to 17.5 g of NH4Cl and dilute to 250 mL

• Dissolve 0.2 g of solid indicator in 15 mL of triethanolamine

• Mix 50 mL of ethanol with 50 mL of water

At what pH is calcium hardness determined in the experiment?

• 
  pH 7

• pH 10

• pH 12

• pH 14

How many samples of the unknown are used to find the accurate value of total Ca²⁺ + Mg²⁺ concentration?

• 
  One sample

• Two samples

• Three samples

• Four samples

What is the unit for expressing the total water hardness in the report?

• 
  mg/L

• g/L

• mg CaCO₃/L

• g CaCO₃/L