Which of the following pairs of elements cannot form an alloy?

If $\bar{a}, \bar{b}, \bar{c}$ are mutually perpendicular vectors having magnitudes $1, 2, 3$ respectively,then $[\bar{a}+\bar{b}+\bar{c} \quad \bar{b}-\bar{a} \quad \bar{c}] = $

Assertion : Tropical rain forests are disappearing fast from developing countries such as India.
Reason : No value is attached to these forests because these are poor in biodiversity.

In which of the following reactions,the concentration of the product is higher than the concentration of reactant at equilibrium? ($K =$ equilibrium constant)

The acceptable level of carbon monoxide gas $(CO)$ in the atmosphere in $ppm$ level is

When a non-volatile solute is added to a solvent,the vapor pressure decreases by $10 \ mm$. The mole fraction of the solute is $0.2$. If the vapor pressure decreases by $20 \ mm$,what will be the mole fraction of the solvent?