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Surface Chemistry — Chemistry STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 ScienceChemistrySurface Chemistry2 Marks
Question
A colloidal solution of ferric oxide is prepared by two different methods as shown below.
  1. What is the charge on colloidal particles in two test tubes $(A)$ and $(B)?$
  2. Give reasons for the origin of charge.
✓

Answer

  1. Colloidal particles of test tube $(A)$ are positively charged whereas colloidal particles of test tube $(B)$ are negatively charged.
  2. In test tube $(A),$ $Fe^{3+}$ is adsorbed on the precipitate $Fe_2O_3.xH_2O [$or $Fe_2O_3.xH_2O/ Fe^{3+}$ is formed$].$
In test tube $(B),\ OH^–$ ion is adsorbed on the precipitate $Fe_2O3 .\ xH_2O [$or $Fe_2O_3.xH_2O/ OH^–$ is formed$].$

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