The charge of " $\mathrm{SnO}_2-\mathrm{sol}^{\prime}$ in alkaline and acidic medium are respectively

(Hint $\mathrm{SnO}_2$ is amphoteric oxide)

To resist the coagulation of 100 cc gold sol; 1 cc of $10 \% \mathrm{NaCl}$ is added to it in the presence of $10^{-4} \mathrm{~g}$ gelatin. The gold number of gelatin is

Which of the following statements is correct for chemisorption?

The gold numbers of gelatin, haemoglobin and sodium acetate are $5 \times 10^{-3}, 5 \times 10^{-2}$ and $7 \times 10^{-1}$, respectively. The protective actions will be in the order