Which one of the following elements does not form solid hydrogen carbonate?
- A.Sodium
- B.Potassium
- C.Caesium
- D.Lithium
Correct answer
Explanation
The correct answer is D, Lithium. Lithium hydrogen carbonate exists only in solution; it cannot be isolated as a solid.
All the alkali metals of group 1 form hydrogen carbonates (bicarbonates), but lithium behaves differently from the rest. The Li⁺ ion is very small and has a high charge density, so it strongly polarises the large hydrogen carbonate ion and cannot hold it in a stable crystal lattice. This is one of the anomalous properties of lithium, which in many ways resembles magnesium, its diagonal neighbour; magnesium hydrogen carbonate too is known only in solution. Sodium hydrogen carbonate, NaHCO₃, is the familiar baking soda used in cooking and fire extinguishers.
A is wrong because sodium forms solid NaHCO₃, baking soda.
B is wrong because potassium forms solid KHCO₃.
C is wrong because caesium, a large alkali metal ion, forms a stable solid hydrogen carbonate.
Exam tip: lithium is the odd one of group 1 and shows a diagonal relationship with magnesium.
Practice Questions
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- A.Galileo
- B.Martin Luther
- C.Johannes Kepler
- D.Copernicus
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- C.Urea is produced from digestion of starch.
- D.Urea is produced in lung and kidney.
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- A.Condenser-Objective lens-Eyepiece-Body tube
- B.Objective lens-Condenser-Body tube-Eyepiece
- C.Condenser-Objective lens-Body tube-Eyepiece
- D.Eyepiece-Objective lens-Body tube-Mirror
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- D.Haemoglobin is only used for blood clotting and not for carrying gases.
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- B.Histones are proteins that are present in nucleus in association with DNA.
- C.Histones are proteins associated with lipids in the cytosol.
- D.Histones are proteins associated with carbohydrates in the cytosol.
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