A sample of potato starch was ground in a ball mill to give a starch-like molecule of lower molecular weight. The product analysed $0.086\%$ Phosphorus. If each molecule is assumed to contain one atom of phosphorus, what is the molecular weight of the material? 

The molecular weight of the material is $\mathrm{z}\times {10}^3 \mathrm{g}$, find $\mathrm{z}$(Nearest integer).

One litre of an acidified solution of ${\mathrm{KMnO}}_4$ containing $15.8 \mathrm{g}$ of ${\mathrm{KMnO}}_4$ is decolourised by passing a sufficient amount of ${\mathrm{SO}}_2$. If ${\mathrm{SO}}_2$ is produced by roasting of iron pyrites $\left({\mathrm{FeS}}_2\right)$, what will be the amount of pyrites (in grams) required to produce the necessary amount of ${\mathrm{SO}}_2$?

(Atomic mass of $\mathrm{K}=39, \mathrm{Mn}=55, \mathrm{S}=32, \mathrm{O}=16, \mathrm{Fe}=56, \mathrm{H}=1$)

Round off your answer to the nearest integer.

An alloy of aluminium and copper was treated with aqueous $\mathrm{HCl}$. The aluminium dissolved according to the reaction $\mathrm{Al}+3{\mathrm{H}}^{+}\to {\mathrm{Al}}^{3+}+\frac{3}{2}{\mathrm{H}}_2$, but the copper remained as a pure metal. A $0.350 \mathrm{g}$ sample of the alloy gave $415 \mathrm{cc}$ of ${\mathrm{H}}_2$ measured at $273 \mathrm{K}$ and $1 \mathrm{atm}$ pressure. What is the weight percentage of $\mathrm{Al}$ in the alloy?

Give the final answer up to first place of decimal after rounding off.

The natural titanium oxide, known as rutile and containing $39.95\%$ of oxygen, is isomorphous with ${\mathrm{SnO}}_2,$ known as cassiterite. Calculate the atomic weight of titanium.

Give the answer up to first place of decimal.

Excess of calcium orthophosphate ${\mathrm{Ca}}_3({\mathrm{PO}}_4{)}_2$ is reacted with magnesium to form calcium phosphide $\left({\mathrm{Ca}}_3{\mathrm{P}}_2\right)$ with magnesium oxide. Calcium phosphide on reacting with an excess of water liberate phosphine gas (${\mathrm{PH}}_3$) along with calcium hydroxide. The evolved phosphine $\left({\mathrm{PH}}_3\right)$ was burnt in the air (excess of oxygen ) to yield phosphorus pentoxide $\left({\mathrm{P}}_2{\mathrm{O}}_5\right)$ along with water. How many grams of magnesium metaphosphate would be obtained, if $19.2\mathrm{g}$ of magnesium were used for reducing calcium phosphate: 

( Atomic wt. of $\mathrm{Mg}=24, \mathrm{P}=31$ )

${\mathrm{Ca}}_3{\left({\mathrm{PO}}_4\right)}_2+ 8\mathrm{Mg}⟶{\mathrm{Ca}}_3{\mathrm{P}}_2+ 8\mathrm{MgO}$
${\mathrm{Ca}}_3{\mathrm{P}}_2+{\mathrm{H}}_2\mathrm{O}⟶\mathrm{Ca}(\mathrm{OH}{)}_2+{\mathrm{PH}}_3$
${\mathrm{PH}}_3+{\mathrm{O}}_2⟶{\mathrm{P}}_2{\mathrm{O}}_5+{\mathrm{H}}_2\mathrm{O}$
$\mathrm{MgO}+{\mathrm{P}}_2{\mathrm{O}}_5⟶\mathrm{Mg}{\left({\mathrm{PO}}_3\right)}_2$

Magnesium metaphosphate