The standard reduction potential of a half-cell measures:
A. Current produced
B. Tendency to gain electrons
C. Tendency to lose electrons
D. Resistance of electrolyte
Answer: Option B
Solution (By JKSSB Mock Tests)
Standard reduction potential (E°) measures the tendency of a species to gain electrons and be reduced. The more positive the E°, the greater the tendency to undergo reduction. Metals with negative E° are good reducing agents (e.g., Zn, -0.76 V). E°cell = E°cathode - E°anode. It is measured under standard conditions (1 M, 1 atm, 25°C) relative to standard hydrogen electrode (SHE) which is assigned 0 V.
Explanation:
Rusting is a chemical change because iron reacts with oxygen and moisture to form a completely new chemical substance, hydrated iron(III) oxide (Fe₂O₃·xH₂O), which has different chemical properties from iron and cannot be easily reversed by simple physical means like heating or cooling.
Explanation:
Atomic number (Z) = Mass number (A) – Number of neutrons (N) = 39 – 20 = 19. This is potassium (K). Number of protons equals atomic number. In a neutral atom, electrons also equal Z.
Explanation:
Number of half-lives = total time / half-life = 10/5 = 2. Fraction remaining = (1/2)ⁿ = (1/2)² = 1/4. Thus 25% remains. After 3 half-lives (15 years) it would be 1/8.
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