Albumin has a gold number of $0.09$. What is the minimum amount of albumin (in $mg$) required to protect the coagulation of $40 \ mL$ of gold sol from $4 \ mL$ of $10 \% \ NaCl$ solution?

On addition of $1 \, mL$ solution of $10\% \, NaCl$ to $10 \, mL$ gold sol in the presence of $0.25 \, g$ of starch,the coagulation is just prevented. What is the gold number of starch?

The surface tension of a soap solution is $30 \times 10^{-3} \, N/m$. The work done to increase the surface area of a soap film from $5 \, cm \times 5 \, cm$ to $10 \, cm \times 10 \, cm$ is:

Which of the following substances gives a positively charged sol?

Choose the correct reason$(s)$ for the stability of the lyophobic colloidal particles.
$(A)$ Preferential adsorption of ions on their surface from the solution.
$(B)$ Preferential adsorption of solvent on their surface from the solution.
$(C)$ Attraction between different particles having opposite charges on their surface.
$(D)$ Potential difference between the fixed layer and the diffused layer of opposite charges around the colloidal particles.

Which of the following is not a negatively charged sol?