Chemistry
Identify the substance underlined in each of the following:
(i) The electrode that increases in mass during the electro-refining of silver.
(ii) The acid that is a dehydrating as well as a drying agent.
(iii) The catalyst used to oxidize ammonia into nitric oxide.
Electrolysis
ICSE 2020
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Answer
(i) Cathode
Reason — Pure copper is deposited on the thin sheet of pure copper placed at the cathode
(ii) Sulphuric acid
Reason — Being hygroscopic sulphuric acid absorbs moisture but not enough to form a solution. Hence, it is a drying agent.
Sulphuric acid is a dehydrating agent as it can remove chemically combined water molecules from blue vitriol.
CuSO4.5H2O + H2SO4 ⇌ CuSO4 + 5H2O
(iii) Platinum
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(i) State the volume occupied by 40 gm. of methane at stp if it's vapour density is 8.
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Identify the salts P, Q, R from the following observations:
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(ii) Salt Q is white in colour. On strong heating, it produces buff yellow residue and liberates reddish brown gas. Solution of salt Q produces chalky white insoluble ppt. with excess of ammonium hydroxide.
(iii) Salt R is black in colour. On reacting with conc. HCl, it liberates a pungent greenish yellow gas which turns moist starch iodide paper blue black.
Copy and complete the following paragraph using the options given in brackets:
Alkenes are a homologous series of (i) …………… [saturated/unsaturated] hydrocarbons characterized by the general formula (ii) …………… [CnH2n+2/CnH2n]. Alkenes undergo (iii) …………… [addition/substitution] reactions and also undergo (iv) …………… [hydrogentaion/dehydrogenation] to form alkanes.
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A: Neutralization
B: Precipitation
C: Titration(i) Copper sulphate
(ii) Zinc carbonate
(iii) Ammonium sulphate