Which gas is released when $Na_2CO_3$ is heated?

The work function of a substance is $4.0 \, eV$. The longest wavelength of light that can cause photoelectron emission from this substance is approximately ............ $nm$.

Which group of organisms was the first to exist on Earth among the given options?

The pairs of straight lines $x^2-3xy+2y^2=0$ and $x^2-3xy+2y^2+x-2=0$ form a

If $\cos (x-y), \cos x, \cos (x+y)$ are three distinct numbers which are in harmonic progression and $\cos x \neq \cos y$,then $1+\cos y$ is equal to

The binding energy per nucleon versus mass number curve for nuclei is shown in the figure. $W, X, Y$ and $Z$ are four nuclei indicated on the curve. The process that would release energy is