Solder is an alloy of

Identify the products of the reaction: $4FeCr_2O_4 + 8Na_2CO_3 + 7O_2 \rightarrow ?$

Which of the following is not correctly matched?

The percentage $(\%)$ of silver in the alloy German silver is:

Given below are two statements related to Ellingham diagram:
Statement-$I$ : Ellingham diagrams can be constructed for formation of oxides,sulfides and halides of metals.
Statement-$II$ : It consists of plots of $\Delta_f H^0$ vs $T$ for formation of oxides of elements.
In the light of the above statements,choose the most appropriate answer from the options given below:

Which among the following statement$(s)$ is(are) true for the extraction of aluminium from bauxite?
$A$. Hydrated $Al_2O_3$ precipitates,when $CO_2$ is bubbled through a solution of sodium aluminate.
$B$. Addition of $Na_3AlF_6$ lowers the melting point of alumina.
$C$. $CO_2$ is evolved at the anode during electrolysis.
$D$. The cathode is a steel vessel with a lining of carbon.