Chemistry
State one observation :
(a) Concentrated nitric acid is reacted with sulphur.
(b) Lead nitrate is heated strongly in a test tube.
(c) Zinc nitrate crystals are strongly heated.
(d) when crystals of copper nitrate are heated in a test tube.
Nitric Acid
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Answer
(a) When concentrated nitric acid is reacted with sulphur, dense brown fumes of nitrogen dioxide are observed.
S + 6HNO3 [conc.] ⟶ H2SO4 + 2H2O + 6NO2
(b) Lead nitrate decomposes on heating to give nitrogen dioxide, oxygen gas and yellow residue of lead oxide which fuses with the glass of the test tube.
2Pb(NO3)2 2PbO + 4NO2 + O2
(c) Reddish brown nitrogen dioxide gas is evolved on heating zinc nitrate crystals.
(d) Reddish brown nitrogen dioxide gas is evolved.
Black coloured residue of CuO is obtained in the test tube.
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Explain why
(a) Only all-glass apparatus should be used for the preparation of nitric acid by heating concentrated sulphuric acid and potassium nitrate.
(b) Nitric acid is kept in a reagent bottle for a long time.
(c) Iron is rendered passive with fuming HNO3. Give reason.
(d) Dil. HNO3 is generally considered a typical acid but not so in it's reaction with metals.
(e) When it is left standing in a glass bottle, concentrated nitric acid appears yellow.
A dilute acid B does not normally give hydrogen when reacted with metals but does give a gas when reacts with copper. Identify B. Write equation with copper.
What is the property of nitric acid which allows it to react with copper?
Give balanced equation for the following :
(a) dilute nitric acid and copper carbonate.
(b) oxidation of carbon with conc. HNO3.
(c) Laboratory preparation of nitric acid.
(d) Action of heat on a mixture of copper and concentrated nitric acid.