A compound contains 28% nitrogen and 72% of a metal by weight. Three atoms of metal combine with two atoms of nitrogen. If the atomic weight of nitrogen is 14, the atomic weight of the metal is:

A student heats 40.0 g of a mixture containing magnesium carbonate and some inert impurities. Upon complete decomposition, 8.0 g of magnesium oxide is formed. Calculate the percentage by mass of magnesium carbonate in the original mixture. (Atomic weight: $Mg = 24$)

The number of moles of hydrogen molecules required to produce 20 moles of ammonia through Haber’s process is:

Number of moles of $N{a_2}S{O_4}$ produced from 1 mole of NaOH

0.3 g of an oxalate salt was dissolved in 100 mL solution. The solution required 90 mL of $N/20$ ${\rm{KMn}}{{\rm{O}}_4}$ for complete oxidation. The % of oxalate ion in salt is:

What is the minimum volume (in mL) of a 17.0% $\AgNO_3$ solution required to completely precipitate all chloride ions from 100 mL of a 5.8% NaCl solution?

A 0.50 $M$ solution of $KI$ reacts with excess of ${{\rm{H}}_2}{\rm{S}}{{\rm{O}}_4}$ and ${\rm{KI}}{{\rm{O}}_3}$ solutions according to the equation, $6{{\rm{H}}^ + } + 5{{\rm{I}}^ - } + {\rm{IO}}_3^ - o 3{{\rm{I}}_2} + 3{{\rm{H}}_2}{\rm{O}}$. Which of the following statements is true?

25.0 g of a calcium carbonate sample decomposes on heating to give carbon dioxide and 10.0 g calcium oxide. What will be the percentage purity of calcium carbonate in the sample? (Atomic weight: $Ca = 40$)

Which of the following contains the greatest number of helium atoms?

A mixture of ${\rm{2}}{\rm{.3}}\,\,{\rm{g}}$ formic acid and ${\rm{4}}{\rm{.5}}\,\,{\rm{g}}$ oxalic acid is treated with conc. ${{\rm{H}}_{{\rm{2}}\,}}{\rm{S}}{{\rm{o}}_{\rm{4}}}$ . The evolved gaseous mixture is passed through ${\rm{KOH}}$ pellets weight (in g) of the remaining product at STP will be

Upon heating, 15.0 g of impure zinc carbonate decomposes completely to produce zinc oxide and carbon dioxide. If 5.6 g of zinc oxide is formed, calculate the percentage purity of the zinc carbonate sample. (Atomic weight: $Zn = 65.4$)