Which of the following is a conjugate acid-base pair?

If $10$ volumes of dihydrogen gas reacts with $5$ volumes of dioxygen gas,how many volumes of water vapour would be produced?

An ideal gas of mass $m$ in a state $A$ goes to another state $B$ via three different processes as shown in the figure. If ${Q_1}, {Q_2}$ and ${Q_3}$ denote the heat absorbed by the gas along the three paths,then

For the hyperbola $\frac{x^2}{\cos^2 \alpha} - \frac{y^2}{\sin^2 \alpha} = 1$,which of the following remains constant if $\alpha$ varies?

In the reaction,the major product formed is:

Which is the major product of the following reaction?