Analysis of salts in water - CH18 Revision

What type of information does gravimetric analysis provide?

• Qualitative

• Quantitative

• Both qualitative and quantitative

• Neither qualitative nor quantitative

Electrical conductivity testing provides information about

• the concentration of a sodium chloride in water

• the amount of precipitate in water

• the concentration of ions in water

• the amount of sodium chloride ions in water

Water samples with a high salt concentration have

• higher electrical conductivity

• lower electrical conductivity

If the mole ratio f ion A: ion B is 2:1 then the mass of chemical A is

• double the mass of ion B

• half the mass of ion B

• unable to be determined using the information provided

A calibration curve is used in colorimetry to

• determine the concentration of an ion with known absorbance of light

• visualise the inverse relationship between ion concentration and light absorbance

• visualise the proportional relationship between ion concentration and light absorbance

• determine the absorbance of an ionic solution with a known concentration

An intensely orange coloured solution was analysed using colorimetry. Which of the following statements is not true?

• The concentration of ions in the solution is inversely proportional to the amount of light detected by the detector

• If the colour of the solution is as a result of the ion, a darker solution means more light will be absorbed

• A blue/violet light should be used

• The solution becomes a lighter orange during analysis

Which option correctly describes the difference between colorimetry and UV-visible spectroscopy?

• Ultraviolet electromagentic radiation is used in UV-visible spectroscopy instead of visible light

• A monochromator is used in UV-visible spectroscopy to produce more accurate results than colorimetry

• UV-visible spectroscopy produces an emission spectrum to produce more accurate results than colorimentry

UV-visible spectroscopy was used to measure the spectra of solutions A and B. These spectra are shown below.

If 10 mL of solution A and 10 mL of solution B were mixed, which wavelength should be used to measure the absorbance of solution B?

• 325

• 375

• 600

• 325 or 600

The flame test produces flames with different colours fue to

• differences in the amount of energy required to excite electrons to a higher energy level

• different wavelengths of light being absorbed by different materials in the flame

Which of the following statements are true?

• AAS cannot produce an emission spectrum as insufficient energy is being put into the sample

• AES uses a calibration curve to determine the concentration of an ion in solution

• AAS observations are based on the return of electrons from an excited state to the ground state

• AES can be used for qualitative analysis