Chapter 16 Analysis for Salts

Which of the following is not a heavy metal?

• Cd

• Cr

• K

• Pb

Organometallic heavy metal compounds are a contaminant of concern because

• they can be more soluble than inorganic metal compounds and therefore enter the food-chain easily.

• they are compounds that contain carbon.

• they are naturally produced in the environment and therefore exist naturally in food-chains.

• they are produced when organisms decay.

Which of the following statements regarding electrical conductivity is/are correct.

(I) conductivity increases as the concentration of ions increases

(II) conductivity readings can identify specific ions

(III) conductivity readings will be zero if the concentration of cations and anions is equal

(IV) conductivity readings will be recorded even when the concentration of ions is low

• II & III

• I & IV

• I, III & IV

• all statements are correct

Name the following hydrate:  NaCl.5H₂O

• sodium chloride 
• sodium monochloride pentahydrate
• sodium chloride pentahydrate
• pentahydrate

A 15.67 g sample of a hydrate of magnesium carbonate was heated to drive off the water. The mass was reduced to 7.58 g. What is the formula of the hydrate?

• MgCO₃ · 5H₂O
• MgCO₃ · 4H₂O
• MgCO₃ · 6H₂O
• MgCO₃ · H₂O

• 6.70 g

• 19.7 g

• 9.83 g

• 4.91 g

• 27.1 mL

• 39.1 mL

• 13.6 mL

• 54,.2 mL

• 3.07 %

• 0.259 %

• 7.53 %

• 1.86 %

When using colorimetry to analyse a blue solution, the colour of light which should be used is

• blue.

• orange.

• green.

• violet.

A colorimeter is used to analyse the concentration of iron(II) ions (Fe²⁺) in the water in a tank. The calibration curve shown left was obtained from measuring the absorbance of a series of standards. The iron solution is diluted from 5 mL to 20 mL before its absorbance is measured to be 0.24. What is the concentration of Fe²⁺ in the original tank water sample?

• 0.15 M

• 0.60 M

• 0.24 M

• 0.96 M