Chemical $A$ is used for water softening to remove temporary hardness. $A$ reacts with sodium carbonate to generate caustic soda. When $CO_2$ is bubbled through $A$,it turns cloudy,what is $A$?

Water is used to cool radiators of engines in cars because:

Which of the following sulfates is insoluble in water?

The packing efficiency of the two-dimensional square unit cell shown below is ........... $\%$

An object of mass $0.2 \, kg$ executes simple harmonic motion along the $X$-axis with a frequency of $\frac{25}{\pi} \, Hz$. At the position $x = 0.04 \, m$,the object has a kinetic energy of $0.5 \, J$ and a potential energy of $0.4 \, J$. The amplitude of oscillation in meters is equal to:

The resistance in the following circuit is increased at a particular instant. At this instant,the value of resistance is $10 \, \Omega$. The current in the circuit will be now: