When two ice cubes are pressed over each other,they unite to form one block. Which of the following forces is responsible for holding them together?

$KF$ combines with $HF$ to form $KHF_2$. Which of the following species are present in this compound?

The melting point of $o$-hydroxybenzaldehyde $(A)$ is lower than that of $p$-hydroxybenzaldehyde $(B)$. This is because

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$: Dipole-dipole interactions are the only non-covalent interactions resulting in hydrogen bond formation.
Reason $R$: Fluorine is the most electronegative element and hydrogen bonds in $HF$ are symmetrical.

The boiling points of $HF$, $HCl$, $HBr$ and $HI$ follow the order:

Hydrogen bond energy is equal to