What type of solution is brass?

What is the significance of Henry's Law constant $K_H$?

At $293 \ K$,the Henry law constant in water for $N_2$ and $O_2$ are $76.48 \ kbar$ and $34.86 \ kbar$ respectively. What is the ratio of mole fractions of $N_2$ and $O_2$ in water? (Assume partial pressures of $N_2$ and $O_2$ are the same at $293 \ K$)

The air is a mixture of a number of gases. The major components are oxygen and nitrogen with approximate proportions of $20 \%$ and $79 \%$ by volume at $298 \ K$. The water is in equilibrium with air at a total pressure of $10 \ atm$. At $298 \ K$,if the Henry's law constants for oxygen and nitrogen are $3.30 \times 10^{7} \ mm \ Hg$ and $6.51 \times 10^{7} \ mm \ Hg$ respectively,calculate the mole fractions of these gases in water.

If the solubility of $NaCl$ at $20\,^{\circ}C$ is $35\,g$ per $100\,g$ of water,then on adding $50\,g$ of $NaCl$ to the same amount of water at the same temperature,the amount of salt that remains undissolved is .......... $g$.

Solubility of iodine in water may be increased by adding