Chemical reactions and equations Activity Based Question 10th Chemistry
Q.
A student added a few pieces of zinc into dil.H₂SO₄
taken in a test tube. Suddenly, evolution of gas occurs. What gas is
evolved?
Answer:
Hydrogen gas
Q.
Why do copper sulphate crystals change colour from blue to white on heating?
Answer:
Due to lose of water of crystallization which can also be called as dehydration
Q. What happens when a small piece of iron is
kept in copper sulphate solution?
Answer:
Simple displacement reaction results in the Formation of a brown coating of
copper on the surface of iron nail. The green colour of the solution is due to
the displaced Fe²⁺ ions from the
Iron nail
Q. While performing an experiment, a student
adds sodium sulphate solution to a colourless solution. A white precipitate is
immediately formed and is insoluble in dil. HCl. The colourless solution is
…………………………… and the precipitate formed is……………………
Answer:
Barium chloride reacts with sodium sulphate to form a white precipitate of
barium sulphate[BaCl₂ and
BaSO₄]
Q. When NaOH is added to zinc sulphate solution,
a precipitate is formed which is soluble in excess of NaOH. The precipitate
obtained is……………………. & the colour of the precipitate is……………….
Answer:
A white gelatinous precipitate of zinc hydroxide is formed Zn(OH)₂
& white gelatinous
Q.
On heating Pb(NO₃)₂,
what is observed during the reaction?
Answer: Lead nitrate decomposes on strong heating
with a crackling sound. It produces NO₂ (g), O₂
(g) and PbO (s)
Q. Take dilute sulphuric acid in a test tube and
put a few zinc granules into the test tube. What will you observe?
Answer:
Since Zn and dil H₂SO₄ react with
each other liberating H₂ gas, the size of zinc granules keep
on decreasing
Q. When magnesium combines with oxygen, it
produces magnesium oxide that appears to be like:
Answer:int:
Mg combines with O₂ to form a white ash of MgO
Q. 100 ml of a saturated copper sulphate
solution was taken in a beaker. A small amount of iron filings was added to the
beaker and left undisturbed overnight. The mixture was then filtered to obtain
the residue. The residue was found to be what colour?
Answer:
In this reaction copper particles are obtained which appears as reddish brown
residue.
Q. When you place an iron nail in copper
sulphate solution, the reddish brown coating formed on the nail is _______.
Answer:
The reddish brown coating is a soft and dull coating of copper
Q. What is observed when dilute sulphuric acid
is added to zinc granules?
Answer:
Zn reacts with dil. H₂SO₄ to liberate H₂
gas and bubbles start coming from the surface of the Zinc granules.
Q.
Why is magnesium ribbon held with a pair of tongs and not with bare hands, when
it is burnt in air?
Answer: Magnesium metal is a good conductor of heat,
so it gets very hot when it is held in the flame.
VERY VALID QUESTIONS FOR CHEM.. CLASS 10TH(CBSE) BOARD
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