Which one of the following removes temporary hardness of water?

Three charges $2q, -q$ and $-q$ are located at the vertices of an equilateral triangle. At the centre of the triangle,

When heat is supplied to a diatomic gas,it expands at constant pressure. What fraction of the heat supplied is converted into internal energy?

If $Q$ denotes the set of all rational numbers and $f\left(\frac{p}{q}\right)=\sqrt{p^2-q^2}$ for any $\frac{p}{q} \in Q$,then observe the following statements.
$I$. $f\left(\frac{p}{q}\right)$ is real for each $\frac{p}{q} \in Q$
$II$. $f\left(\frac{p}{q}\right)$ is a complex number for each $\frac{p}{q} \in Q$.
Which of the following is correct?

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

Thermodynamically the most stable form of carbon is