On adding 1ml solution of 10% NaCl to 10ml gold sol in the presence of 0.25g of starch, the coagulation is just prevented. Starch has the following gold number:
Correct answer: C. 2.5
- A. 0.025
- B. 0.25
- C. 2.5
- D. 250
Explanation
Gold number is 'least quantity of protective colloid in milligrams, which is just sufficient to prevent the coagulation of 10 ml of standard gold sol (containing 0.0053% gold) by the rapid adidition of 1 ml of 10% NaCl solution.
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Solutions are described using molarity, molality, normality, mole fraction, percentage concentration and parts per million. Coverage also includes vapour-pressure lowering, boiling-point elevation, freezing-point depression and osmotic pressure, then distinguishes true solutions, colloids and suspensions by particle size, stability, light scattering and settling.
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