Assertion (A): Boiling water removes temporary hardness. Reason (R): Boiling converts soluble bicarbonates into insoluble carbonates.
A. Both A and R are true but R is NOT the correct explanation of A.
B. Both A and R are true and R is the correct explanation of A.
C. A is true but R is false.
D. A is false but R is true.
Answer: Option B
Solution (By JKSSB Mock Tests)
Temporary hardness is due to Ca(HCO₃)₂ and Mg(HCO₃)₂. Upon boiling, these decompose into insoluble CaCO₃ and Mg(OH)₂, which precipitate out and can be filtered. Thus, boiling effectively removes temporary hardness, and R correctly explains the chemical mechanism involved.
Explanation:
Ethylene (C₂H₄) is systematically named ethene. The -ene suffix indicates a double bond. Ethane is C₂H₆, ethyne (acetylene) is C₂H₂, methane is CH₄. Ethene is an important petrochemical used to make polythene.
Explanation:
Iodine-131 is a radioactive isotope used to treat thyroid disorders including goitre and cancer. Carbon-14 for dating, Cobalt-60 for cancer therapy, Uranium-235 as fuel in nuclear reactors. Non-radioactive isotopes are used as tracers. Goitre is often caused by iodine deficiency, but radioactive iodine can be used therapeutically.
Explanation:
In chlor-alkali process (electrolysis of concentrated NaCl solution), Cl⁻ ions are oxidized at the anode: 2Cl⁻ → Cl₂(g) + 2e⁻ (chlorine gas). At the cathode, H₂O is reduced: 2H₂O + 2e⁻ → H₂(g) + 2OH⁻, producing hydrogen gas and leaving NaOH in solution. The process uses a diaphragm or membrane cell to keep products separate. Chlorine is used for water treatment and PVC.
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