<h3>Ferric Oxide:-</h3>


<h3><u>C</u><u>a</u><u>l</u><u>c</u><u>i</u><u>u</u><u>m</u><u> </u><u>H</u><u>y</u><u>d</u><u>r</u><u>o</u><u>x</u><u>i</u><u>d</u><u>e</u><u>:</u><u>-</u></h3>


At constant temperature and pressure, increasing the amount of gas will increase the volume.
The residue of coal decomposition in the manufacture of steel is coal tar. It is a by product of the coking process in the blast furnace. Coal gas is another by product but is not the answer becuase this is not a residue which is a solid. Coal gas is a gas. Coke in fact is one of the reactants fed for steel making. Answer is choice 3.
B. Compound
Calcium nitrate is an inorganic compound