A solution with a pH of 2 is how many times more acidic than a solution with a pH of 5?
A. 10 times
B. 3 times
C. 1000 times
D. 100 times
Answer: Option C
Solution (By JKSSB Mock Tests)
pH difference = 3 units. Since pH is logarithmic (base 10), [H⁺] ratio = 10³ = 1000. So pH 2 solution has 1000 times greater H⁺ concentration, making it 1000 times more acidic.
Assertion (A): Detergents are more effective than soaps in hard water. Reason (R): Detergents do not form insoluble precipitates with calcium and magnesium ions.
A.A is true but R is false.
B.A is false but R is true.
C.Both A and R are true and R is the correct explanation of A.
D.Both A and R are true but R is NOT the correct explanation of A.
Explanation:
Soaps react with Ca²⁺ and Mg²⁺ ions in hard water to form insoluble scum (calcium/magnesium stearate), wasting soap and reducing cleaning efficiency. Detergents form soluble salts with these ions, so they lather well and clean effectively in hard water. Both statements are correct and R explains A.
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 Thomson's model (plum pudding) was later superseded.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:
According to the reactivity series, zinc is more reactive than copper, so Zn displaces Cu: Zn + CuSO₄ → ZnSO₄ + Cu. Silver, gold, and mercury are less reactive than copper and cannot displace it. Reactivity: K > Na > Ca > Mg > Al > Zn > Fe > Pb > Cu > Ag > Au. Displacement reactions are used in metallurgy and galvanic cells. The blue color of CuSO₄ fades as copper is deposited.
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