Which of the following is an example of a strong base?
A. Ca(OH)₂ (slightly soluble)
B. Mg(OH)₂
C. NaOH
D. NH₄OH
Answer: Option C
Solution (By JKSSB Mock Tests)
NaOH is a strong base, fully dissociating into Na⁺ and OH⁻ ions. NH₄OH is a weak base. Ca(OH)₂ and Mg(OH)₂ are sparingly soluble but are considered strong bases in terms of dissociation of dissolved portion, but NaOH is the strongest among common ones.
Explanation:
J.J. Thomson discovered the electron through cathode ray tube experiments in 1897 and measured the e/m ratio by applying electric and magnetic fields. Rutherford discovered the nucleus via the gold foil experiment. Chadwick discovered the neutron (1932). Bohr proposed the planetary model of the atom with quantized orbits. Thomson's model (plum pudding) was later superseded. Exam memory: Thomson = electron (e/m); Rutherford = nucleus; Chadwick = neutron; Bohr = energy levels.
Explanation:
A negative catalyst (inhibitor) decreases the rate of a reaction by increasing activation energy or destroying active intermediates. Example: phosphoric acid inhibits H₂O₂ decomposition. Positive catalysts speed up, enzymes are biocatalysts, autocatalysts are products that catalyze their own formation.
Explanation:
Methyl orange is red at pH < 3.1 and yellow at pH > 4.4. Litmus: red in acid, blue in base. Phenolphthalein: colorless in acid, pink in base. Turmeric: yellow in acid, reddish-brown in base.
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