Which sample contains the largest number of atoms?

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

Assume that a human body requires $2500 \, kcal$ of energy each day for metabolic activity and sucrose is the only source of energy,as per the equation $C_{12}H_{22}O_{11(s)} + 12 \, O_{2(g)} \longrightarrow 12 \, CO_{2(g)} + 11 \, H_2O_{(l)};$ $\Delta H = -5.6 \times 10^6 \, J$. (Fill in the blanks) $(a)$ The energy requirement of the human body per day is $.... \, kJ$. $(b)$ The mass of sucrose required to provide this energy is $........ \, g$ and the volume of $CO_2$ (at $STP$) produced is $......... \, litres.$

Which of the following should be done in order to prepare $0.40 \ M \ NaCl$ starting with $100 \ mL$ of $0.30 \ M \ NaCl$ (mol.wt. of $NaCl = 58.5$)?

Select the correct option based on the given figure. Symbol $T$ indicates a true statement and $F$ indicates a false statement.
Solution $P = 8 \, N$ $H_2SO_{4(aq)}$ and Solution $Q = 8 \, N$ $HNO_{3(aq)}$.
$(1)$ The number of moles of solute in solution $P$ and solution $Q$ are equal.
$(2)$ The number of gram-equivalents of solute in solution $P$ and solution $Q$ are equal.
$(3)$ The mole fraction of solvent in solution $P$ and solution $Q$ are equal.
$(4)$ The concentration of $H^+_{(aq)}$ in solution $P$ and solution $Q$ are equal.

At $T(K)$,a gaseous mixture contains $H_2$ and $O_2$. The total pressure of the mixture is $2 \ bar$. The partial pressure of $H_2$ is $1.778 \ bar$. What is the weight $(w/w)$ percentage of $H_2$ in the mixture?