Cement is a mixture of: MCQ with Answer and Explanation

Explanation:
Sodium bicarbonate (NaHCO₃) is used in soda-acid fire extinguishers. It reacts with sulfuric acid to produce CO₂, which smothers the fire. Also, dry powder extinguishers use NaHCO₃. It is also baking soda.

Explanation:
The chief impurity in iron ores (hematite, magnetite) is silica (SiO₂), which is acidic gangue. In the blast furnace, limestone (CaCO₃) is added as flux; it decomposes to CaO, which combines with silica to form fusible calcium silicate slag: CaO + SiO₂ → CaSiO₃. This slag floats on molten iron and is removed. Alumina may also be present but silica is the primary impurity.

Explanation:
Ernest Rutherford, in 1911, along with Geiger and Marsden, bombarded a thin gold foil with alpha particles. Most passed through, some were deflected at large angles, leading to the nuclear model of the atom—a small, dense, positively charged nucleus with electrons around it. Thomson's plum pudding model predicted no large deflections. Chadwick discovered neutron.