Boron has two stable isotopes,$^{10}B$ $(19\%)$ and $^{11}B$ $(81\%)$. What will be its atomic mass in the periodic table?

If we consider that $1/6$ of the mass of a carbon atom,in place of $1/12$,is taken to be the relative atomic mass unit,the mass of one mole of a substance will

Complete reaction of $2.0 \, g$ of calcium (at. wt. $= 40$) with excess $HCl$ produces $1.125 \, L$ of $H_2$ gas. Complete reaction of the same quantity of another metal $M$ with excess $HCl$ produces $1.85 \, L$ of $H_2$ gas under identical conditions. The equivalent weight of $M$ is closest to

Which of the following properties of an element is not variable?

An oxide of an element contains $67.67\%$ oxygen and the vapour density of its volatile chloride is $79$. What is the atomic weight of the element?

Assuming chlorine element has two isotopes as $Cl^{35}$ and $Cl^{37}$ with their percentage abundance as $25\%$ and $75\%$ respectively. Find the average atomic weight.