Pakistan MCQs

Temporary hardness is caused mainly by bicarbonates.
Boiling converts them into insoluble precipitates.

Alloys combine metals with other elements.
They are designed for strength, corrosion resistance, or other useful properties.

Brass contains mainly copper and zinc.
It is used in fittings, instruments, and decorative items.

Bronze is primarily copper alloyed with tin.
It is harder than pure copper.

Steel contains iron with a controlled amount of carbon.
Other alloying elements can modify its properties.

Chromium in stainless steel creates a thin passive oxide film.
This layer limits further corrosion.

Copper conducts electricity well and can be drawn into wires.
It is also relatively resistant to corrosion.

Aluminium has a low density and good corrosion resistance.
Its alloys are widely used in aircraft.

Acid-carbonate reactions form a salt, water, and carbon dioxide.
The gas causes visible bubbling.

Rusting is an oxidation process requiring oxygen and moisture.
It weakens exposed iron over time.

Baking soda is sodium hydrogen carbonate, NaHCO₃.
It releases carbon dioxide when heated or mixed with acid.

Galvanization covers iron or steel with zinc.
The coating blocks moisture and can protect sacrificially.