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) Copper nitrate crystals 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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Related Questions
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.
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.
X, Y and Z are three crystalline solids which are soluble in water and have a common anion.
To help you to identify X, Y and Z, you are provided with the following experimental observations. Copy and complete the corresponding inferences in (a) to (e).(a) A reddish-brown gas is obtained when X, Y and Z are separately warmed with concentrated sulphuric acid and copper turning added to the mixture.
INFERENCE 1: The common anion is the …………… ion.
(b) When X is heated, it melts and gives off only one gas which re-lights a glowing splint.
INFERENCE 2: The cation in X is either …………… or ……………
(c) The action of heat on Y produces a reddish-brown gas and a yellow residue which fuses with the glass of the test tube.
INFERENCE 3: The metal ion present in Y is the …………… ion.
(d) When Z is heated, it leaves no residue. Warming Z with sodium hydroxide solution liberates a gas which turns moist red litmus paper blue.
INFERENCE 4: Z contains the …………… cation.
(e) Write the equations for the following reactions.
- X and concentrated sulphuric acid (below 200° C). (One equation only for either of the cations given in INFERENCE 2).
- Action of heat on Y.
- Concentrated nitric acid is added to copper turnings kept in a beaker.