Baking powder contains sodium bicarbonate (NaHCO₃) and a weak solid acid such as tartaric acid or cream of tartar (potassium hydrogen tartrate). When moistened, they react to produce CO₂, making dough rise. Baking soda alone requires an acidic ingredient (yogurt, lemon). The acid in baking powder ensures reliable leavening. Sodium chloride and calcium carbonate do not serve this purpose.
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:
Sodium reacts vigorously with moisture and oxygen in air, so it is stored under kerosene to prevent contact. Potassium, lithium are similarly stored. Iron, zinc, copper do not require such storage.
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