What is the percentage of lead in a lead pencil (in $\%$)?

You are given $500 \ mL$ of $2 \ N \ HCl$ and $500 \ mL$ of $5 \ N \ HCl$. What will be the maximum volume of $3 \ M \ HCl$ that you can make from these two solutions? .............. $mL$

Who is called the father of chemistry?

When $100 \, mL$ of $1 \, M$ $NaOH$ and $10 \, mL$ of $10 \, N$ $H_2SO_4$ solutions are mixed,what will be the nature of the resulting solution?

$(i)$ Calculate the total number of electrons present in one mole of methane.
$(ii)$ Find $(a)$ the total number and $(b)$ the total mass of neutrons in $7 \, mg$ of $^{14}C$. (Assume that mass of a neutron $= 1.675 \times 10^{-27} \, kg$).
$(iii)$ Find $(a)$ the total number and $(b)$ the total mass of protons in $34 \, mg$ of $NH_3$. Will the answer change if the temperature and pressure are changed?

$4 \ g$ equimolar mixture of $NaOH$ and $Na_{2}CO_{3}$ contains $x \ g$ of $NaOH$ and $y \ g$ of $Na_{2}CO_{3}$. The value of $x$ is $..... \ g$. (Nearest integer)