PPSC MCQs

Hardness ions react with soap molecules.
The insoluble products waste soap and reduce lather.

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.

Citrus fruits such as lemons and oranges contain citric acid.
It contributes to their sour taste.

Muscle cells can produce lactate during anaerobic metabolism.
This supports short-term energy production when oxygen delivery is limited.

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.