What is the chemical formula of Tin $(IV)$ oxide?

Concentrated sulfuric acid is $95\%$ by weight and its density is $1.8 \ g \ cm^{-3}$. What volume of concentrated acid in $cm^3$ is required to prepare $4 \ L$ of $0.4 \ M \ H_2SO_4$ solution (in $.7$)?

What is the volume (in litres) of oxygen required at $STP$ to completely convert $1.5 \ mol$ of sulphur into sulphur dioxide?

In the combustion of $2.0 \ g$ of methane,$25 \ kcal$ of heat is liberated. The heat of combustion of methane would be ..... $kcal$.

$x \ g$ of methane was burnt completely in the presence of oxygen. The liberated gases were passed into a solution containing $370 \ g$ of $Ca(OH)_2$. The weight of white precipitate obtained was $500 \ g$. What is the value of $x$ (in $g$)? (Given: $C=12, H=1, Ca=40, O=16 \ u$)

$A$ solution of $H_2SO_4$ is $31.4 \%$ $H_2SO_4$ by mass and has a density of $1.25 \ g \ mL^{-1}$. The molarity of the $H_2SO_4$ solution is . . . . . . $M$ (nearest integer) [Given molar mass of $H_2SO_4 = 98 \ g \ mol^{-1}$]