$A$ gaseous mixture contains $50\%$ Helium and $50\%$ Methane by volume. What is the percentage of Methane by weight in the mixture?

Three solutions of $HCl$ having normalities $12 \ N$,$6 \ N$,and $2 \ N$ are mixed to obtain a solution of $4 \ N$ normality. Which among the following volume ratios is incorrect for the above mixture?

$12 \ g$ of $Mg$ (atomic mass $24$) on reacting completely with acid gives hydrogen gas,the volume of which at $STP$ would be ............... $L$.

$5 \, M$ solution of $H_2SO_4$ is diluted from $1 \, L$ to $10 \, L$. What is the normality of the solution in $N$?

$14 \ g$ of element $X$ combines with $16 \ g$ of oxygen. Based on this,which of the following statements is incorrect?

$A$ solution of $20.2 \, g$ of $1,2$-dibromopropane in $MeOH$ upon heating with excess $Zn$ produces $3.58 \, g$ of an unsaturated compound $X$. The yield $(\%)$ of $X$ is closest to [Atomic weight of $Br$ is $80$].