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CHEMISTRY [2 Mark Question Answer]

Chemical Reactions · ICSE STD 8 (ICSE - English Medium). 21 questions.

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[2 Mark Question Answer]

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21 questions · timed · auto-graded

Question 12 Marks
What do you observe when Ammonia is brought in contact of hydrogen chloride.gas.
Answer
Ammonia and hydrogen chloride, both compounds, combine to form a compound, ammonium chloride.
$\underset{\text { ammonia }}{\mathrm{NH}_3(\mathrm{~g})}+\underset{\text { hydrogen chloride }}{\mathrm{HCl}(\mathrm{g})} \longrightarrow \underset{\text { ammonium chloride }}{\mathrm{NH}_4 \mathrm{Cl}(\mathrm{s})}$
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Question 22 Marks
What do you observe when Magnesium ribbon is burnt in oxygen.
Answer
Magnesium ribbon bums with a dazzling white light and produces a white powder which is magnesium oxide.
The reaction can be represented as
$\ce{2Mg + O_2 }\rightarrow \ce{2MgO}\  ($white powder$)$
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Question 32 Marks
What do you observe when Lead nitrate is heated.
Answer
The pale yellow solid is lead monoxide, the reddish brown gas is nitrogen dioxide and the colourless gas is oxygen.
$ \underset{\text { lead nitrate }}{2 \mathrm{~Pb}\left(\mathrm{NO}_3\right)_2}(\mathrm{~s}) \xrightarrow{\text { heat }} \underset{\text { lead monoxide }}{2 \mathrm{PbO}(\mathrm{s})}+\underset{\text { nitrogen dioxide }}{4 \mathrm{NO}_2(\mathrm{~g})}+\underset{\text { oxygen }}{\mathrm{O}_2(\mathrm{~g})} $
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Question 42 Marks
Define catalyst.
Answer
A catalyst is a substance that either increases or decreases the rate of a chemical reaction without itself undergoing any chemical change.
$\mathrm{N}_2+3 \mathrm{H}_2 \underset{450^{\circ} \mathrm{C}}{\text { Iron (Catalyst) } 200-900} 2 \mathrm{NH}_3+$ Heat
here iron act as a catalyst and increases the rate of chemical reaction.
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Question 52 Marks
Define neutralization.
Answer
Neutralization: A chemical reaction in which a base or an alkali reacts, with an acid to produce salt and water only.
$\underset{\text { sodium hydroxide }}{\mathrm{NaOH}(\mathrm{aq})}+\underset{\text { hydro chloride acid }}{\mathrm{HCl}(\mathrm{aq})} \longrightarrow \underset{\text { sodium cholride }}{\mathrm{NaCl}(\mathrm{aq})}+\underset{\text { water }}{\mathrm{H}_2 \mathrm{O}}$
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Question 62 Marks
Classify the following reactions as neutralization .Also balance the equations. Also balance the equations.
$(A) \mathrm{CaCO}_3(\mathrm{~s}) \xrightarrow{\text { heat }} \mathrm{CaO}(\mathrm{s})^{+} \mathrm{CO}_2(\mathrm{~g})$
$(B) \mathrm{Zn}(\mathrm{s})+\mathrm{H}_2 \mathrm{SO}_4 \rightarrow \mathrm{ZnSO}_4(\mathrm{~S})+\mathrm{H}_2(\mathrm{~g})$
$ (C) \mathrm{AgNO}_3 (aq) +\mathrm{NaCl}(\mathrm{aq}) \rightarrow \mathrm{AgCl}(\mathrm{S})+\mathrm{NaNO}_3$
$(D) \mathrm{NH}_3(\mathrm{~g})+\mathrm{HCl} (g) \rightarrow \mathrm{NH}_4 \mathrm{Cl} (S)$
$(E) \mathrm{CuSO}_4 (aq) +\mathrm{H}_2 \mathrm{~S} (g) \rightarrow \mathrm{CuS} (S) +\mathrm{H}_2 \mathrm{SO}_4$
$(F) \mathrm{} \mathrm{Zn}(\mathrm{S})+\mathrm{CuSO}_4(\mathrm{aq}) \rightarrow \mathrm{ZnSO}_4 \mathrm{~N} (aq) +\mathrm{Cu}(\mathrm{s})$
$(G) \mathrm{Ca}(\mathrm{s}) \mathrm{O}_2(\mathrm{~g}) \xrightarrow{\text { heat }} \mathrm{CaO}(\mathrm{s})$
$(H) \text { } \mathrm{NaOH}+\mathrm{HCl} \rightarrow \mathrm{NaCl}+\mathrm{H}_2 \mathrm{O} $
$(I) \mathrm{KOH}+\mathrm{H}_2 \mathrm{SO}_4 \rightarrow \mathrm{K}_2 \mathrm{SO}_4+\mathrm{H}_2 \mathrm{O}$
Answer
neutralization Reaction:
$ \text { (H) } \mathrm{NaOH}+\mathrm{HCl} \rightarrow \mathrm{NaCl}+\mathrm{H}_2 \mathrm{O} $
$ \text { (I) } \mathrm{KOH}+\mathrm{H}_2 \mathrm{SO}_4 \rightarrow \mathrm{K}_2 \mathrm{SO}_4+\mathrm{H}_2 \mathrm{O} $
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Question 72 Marks
Classify the following reactions as decomposition, Also balance the equations.
$(A) \mathrm{CaCO}_3(\mathrm{~s}) \xrightarrow{\text { heat }} \mathrm{CaO}(\mathrm{s})^{+} \mathrm{CO}_2(\mathrm{~g})$
$(B) \mathrm{Zn}(\mathrm{s})+\mathrm{H}_2 \mathrm{SO}_4 \rightarrow \mathrm{ZnSO}_4(\mathrm{~S})+\mathrm{H}_2(\mathrm{~g})$
$ (C) \mathrm{AgNO}_3$ (aq) $+\mathrm{NaCl}$ (aq) $\rightarrow \mathrm{AgCl}(\mathrm{S})+\mathrm{NaNO}_3$
$(D) \mathrm{NH}_3(\mathrm{~g})+\mathrm{HCl}(\mathrm{g}) \rightarrow \mathrm{NH}_4 \mathrm{Cl}(\mathrm{S})$
$(E) \mathrm{CuSO}_4$ (aq) $+\mathrm{H}_2 \mathrm{~S}(\mathrm{~g}) \rightarrow \mathrm{CuS}(\mathrm{S})+\mathrm{H}_2 \mathrm{SO}_4(\mathrm{I})$
$(F) \mathrm{} \mathrm{Zn}(\mathrm{S})+\mathrm{CuSO}_4(\mathrm{aq}) \rightarrow \mathrm{ZnSO}_4 \mathrm{~N}(\mathrm{aq})+\mathrm{Cu}(\mathrm{s})$
$(g) \mathrm{Ca}(\mathrm{s}) \mathrm{O}_2(\mathrm{~g}) \xrightarrow{\text { heat }} \mathrm{CaO}(\mathrm{s})$
$(H) \mathrm{NaOH}+\mathrm{HCl} \rightarrow \mathrm{NaCl}+\mathrm{H}_2 \mathrm{O}$
$(I) \mathrm{KOH}+\mathrm{H}_2 \mathrm{SO}_4 \rightarrow \mathrm{K}_2 \mathrm{SO}_4+\mathrm{H}_2 \mathrm{O}$
Answer
precipitation Reaction:
$(C) \mathrm{AgNO}_3 (aq) +\mathrm{NaCl}(\mathrm{aq}) \rightarrow \mathrm{AgCl}(\mathrm{S})+\mathrm{NaNO}_3$
$(E) \mathrm{CuSO}_4 (aq) +\mathrm{H}_2 \mathrm{~S}(\mathrm{~g}) \rightarrow \mathrm{CuS}(\mathrm{S})+\mathrm{H}_2 \mathrm{SO}_4 (I)$
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Question 82 Marks
Classify the following reactions as decomposition, Also balance the equations.
$(A) \mathrm{CaCO}_3(\mathrm{~s}) \xrightarrow{\text { heat }} \mathrm{CaO}(\mathrm{s})^{+} \mathrm{CO}_2(\mathrm{~g})$
$(B) \mathrm{Zn}(\mathrm{s})+\mathrm{H}_2 \mathrm{SO}_4 \rightarrow \mathrm{ZnSO}_4(\mathrm{~S})+\mathrm{H}_2(\mathrm{~g})$
$(C) \mathrm{AgNO}_3 (aq) +\mathrm{NaCl} (aq) \rightarrow \mathrm{AgCl}(\mathrm{S})+\mathrm{NaNO}_3$
$(D)\mathrm{NH}_3(\mathrm{~g})+\mathrm{HCl}(\mathrm{g}) \rightarrow \mathrm{NH}_4 \mathrm{Cl}(\mathrm{S})$
$(E) \mathrm{CuSO}_4 (aq) +\mathrm{H}_2 \mathrm{~S}(\mathrm{~g}) \rightarrow \mathrm{CuS}(\mathrm{S})+\mathrm{H}_2 \mathrm{SO}_4 (I)$
$(F) \mathrm{} \mathrm{Zn}(\mathrm{S})+\mathrm{CuSO}_4(\mathrm{aq}) \rightarrow \mathrm{ZnSO}_4 \mathrm{~N}(\mathrm{aq})+\mathrm{Cu}(\mathrm{s})$
$(g) \mathrm{Ca}(\mathrm{s}) \mathrm{O}_2(\mathrm{~g}) \xrightarrow{\text { heat }} \mathrm{CaO}(\mathrm{s})$
$(H) \mathrm{NaOH}+\mathrm{HCl} \rightarrow \mathrm{NaCl}+\mathrm{H}_2 \mathrm{O} $
$(I) \mathrm{KOH}+\mathrm{H}_2 \mathrm{SO}_4 \rightarrow \mathrm{K}_2 \mathrm{SO}_4+\mathrm{H}_2 \mathrm{O}$
Answer
Displacement Reaction:
$(\mathrm{F}) \mathrm{Zn}(\mathrm{S})+\mathrm{CuSO}_4(\mathrm{aq}) \rightarrow \mathrm{ZnSO}_4 \mathrm{~N}(\mathrm{aq})+\mathrm{Cu}(\mathrm{s}) $
$(B) \mathrm{Zn}(\mathrm{s})+\mathrm{H}_2 \mathrm{SO}_4 \rightarrow \mathrm{ZnSO}_4(\mathrm{~S})+\mathrm{H}_2(\mathrm{~g})$
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Question 92 Marks
Classify the following reactions as decomposition, Also balance the equations.
$(A)\mathrm{CaCO}_3(\mathrm{~s}) \xrightarrow{\text { heat }} \mathrm{CaO}(\mathrm{s})^{+} \mathrm{CO}_2(\mathrm{~g})$
$(B) \mathrm{Zn}(\mathrm{s})+\mathrm{H}_2 \mathrm{SO}_4 \rightarrow \mathrm{ZnSO}_4(\mathrm{~S})+\mathrm{H}_2(\mathrm{~g})$
$(C) \mathrm{AgNO}_3(\mathrm{aq})+\mathrm{NaCl}(\mathrm{aq}) \rightarrow \mathrm{AgCl}(\mathrm{S})+\mathrm{NaNO}_3$
$(D) \mathrm{NH}_3(\mathrm{~g})+\mathrm{HCl}(\mathrm{g}) \rightarrow \mathrm{NH}_4 \mathrm{Cl}(\mathrm{S})$
$(E) \mathrm{CuSO}_4 (aq) +\mathrm{H}_2 \mathrm{~S} (g) \rightarrow \mathrm{CuS}(\mathrm{S})+\mathrm{H}_2 \mathrm{SO}_4 (I)$
$(F) \mathrm{Zn}(\mathrm{S})+\mathrm{CuSO}_4(\mathrm{aq}) \rightarrow \mathrm{ZnSO}_4 \mathrm{~N} (aq) +\mathrm{Cu}(\mathrm{s})$
$(g) \mathrm{Ca}(\mathrm{s}) \mathrm{O}_2(\mathrm{~g}) \xrightarrow{\text { heat }} \mathrm{CaO}(\mathrm{s})
 \text { (H) } \mathrm{NaOH}+\mathrm{HCl} \rightarrow \mathrm{NaCl}+\mathrm{H}_2 \mathrm{O} $
$(I)\mathrm{KOH}+\mathrm{H}_2 \mathrm{SO}_4 \rightarrow \mathrm{K}_2 \mathrm{SO}_4+\mathrm{H}_2 \mathrm{O} x$
Answer
$2.$ Decomposition Reactions:
$\mathrm{CaCO}_3(\mathrm{~s}) \xrightarrow{\text { heat }} \mathrm{CaO}(\mathrm{s})^{+} \mathrm{CO}_2(\mathrm{~g})$
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Question 102 Marks
Classify the following reactions as combination. Also balance the equations.
Also balance the equations.
$(a)\mathrm{CaCO}_3(\mathrm{~s}) \xrightarrow{\text { heat }} \mathrm{CaO}(\mathrm{s})^{+} \mathrm{CO}_2(\mathrm{~g})$
$(b) \mathrm{Zn}(\mathrm{s})+\mathrm{H}_2 \mathrm{SO}_4 \rightarrow \mathrm{ZnSO}_4(\mathrm{~S})+\mathrm{H}_2 (g)$
$(c) \mathrm{AgNO}_3 (aq) +\mathrm{NaCl} (aq) \rightarrow \mathrm{AgCl}(\mathrm{S})+\mathrm{NaNO}_3$
$(d) \mathrm{NH}_3 (g) +\mathrm{HCl}(\mathrm{g}) \rightarrow \mathrm{NH}_4 \mathrm{Cl} (S)$
$(e) \mathrm{CuSO}_4 (aq) +\mathrm{H}_2 \mathrm{~S} (g) \rightarrow \mathrm{CuS}(\mathrm{S})+\mathrm{H}_2 \mathrm{SO}_4$ 
$(f) \mathrm{Zn}(\mathrm{S})+\mathrm{CuSO}_4 (aq) \rightarrow \mathrm{ZnSO}_4 \mathrm{~N} (aq) +\mathrm{Cu} (s)$
$(g) \mathrm{Ca}(\mathrm{s}) \mathrm{O}_2(\mathrm{~g}) \xrightarrow{\text { heat }} \mathrm{CaO}(\mathrm{s})$
$(H)\mathrm{NaOH}+\mathrm{HCl} \rightarrow \mathrm{NaCl}+\mathrm{H}_2 \mathrm{O}$
$(I) \mathrm{KOH}+\mathrm{H}_2 \mathrm{SO}_4 \rightarrow \mathrm{K}_2 \mathrm{SO}_4+\mathrm{H}_2 \mathrm{O}$
Answer
$1.$ Combination reactions.
$(d) \mathrm{NH}_3 (g) +\mathrm{HCl} (g) \rightarrow \mathrm{NH}_4 \mathrm{Cl}(\mathrm{S})$
$(g)\mathrm{Ca}(\mathrm{s}) \mathrm{O}_2(\mathrm{~g}) \xrightarrow{\text { heat }} \mathrm{CaO}(\mathrm{s})$
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Question 112 Marks
What do you observe when when dilute sulphuric acid is added to barium chloride solution ?
Answer
When few drops of dilute sulphuric acid is added to barium chloride solution, a white precipitate of barium sulphate is formed.
$\underset{\text { Barium chloride solution }}{\mathrm{BaCl}_2}+\underset{\text { Sulphuric acid }}{\mathrm{H}_2 \mathrm{SO}_4} \longrightarrow \underset{\text { (Barium sulphate)(White precipitate) }}{\mathrm{BaSO}_4 \downarrow}+\underset{\text { Hydrochloride acid }}{2 \mathrm{HCl}}$
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Question 122 Marks
What do you observe when ferrous sulphate solution is added to an aqueous solution of sodium hydroxide.
Answer
When ferrous sulphate solution is added to sodium hydroxide solution, a dirty green ppt. of ferrous hydroxide is formed.
$\ce{FeSO_4 (aq)} + \ce{2NaOH (aq) → Fe(OH)_2} ↓ +\ce{ Na_2SO_4(aq)}$
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Question 132 Marks
What do you observe when silver nitrate is added to a solution of sodium chloride?
Answer
When a solution of silver nitrate is added to a solution of sodium chloride, white insoluble ppt. of silver chloride is formed.
$\ce{AgNO_3 (aq)} + \ce{NaCl (aq) }\rightarrow \ce{AgCl (ppt)} + \ce{NaNO_3 (aq)}$
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Question 142 Marks
Name three biochemical catalysts found in the human body.
Answer
Biochemical catalysts found in human body:
$1.$ Pepsin
$2.$ Tryspin
$3.$ lipase.
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Question 152 Marks
Define; catalyst.
Answer
Catalyst: A catalyst is a substance that either increases or decreases the rate of a chemical reaction without itself undergoing any chemical change during the reaction.
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Question 162 Marks
How do the following help in bringing about a chemical change? heat.
Answer
Some chemical reactions take place only in the presence of heat.
e.g. When lead nitrate is heated, it breaks into lead monoxide, nitrogen dioxide and oxygen.
$\underset{\text { (lead nitrate) }}{2 \mathrm{~Pb}\left(\mathrm{NO}_3\right)_2} \xrightarrow{\text { heat }} \underset{\text { lead monoxide }}{2 \mathrm{PbO}}+\underset{\text { nitrogen dioxide }}{4 \mathrm{NO}_2}+\mathrm{O}_2$
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Question 172 Marks
How do the following help in bringing about a chemical change? light.
Answer
Some chemical reactions can take place in the presence of light. Ex. Photosynthesis.
$6 \mathrm{CO}_2+6 \mathrm{H}_2 \mathrm{O} \underset{\text { Chlorophyll }}{\stackrel{\text { sunlight }}{\rightleftharpoons}} \mathrm{C}_6 \mathrm{H}_{12} \mathrm{O}_6+6 \mathrm{O}_2$
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Question 182 Marks
How do the following help in bringing about a chemical change? pressure.
Answer
Some chemical reactions take place when reactants are subjected to high pressure.
e.g: Nitrogen and hydrogen when subjected to high pressure produce ammonia gas.
$\mathrm{N}_2+3 \mathrm{H}_2 \underset{200 \mathrm{~atm}}{\stackrel{450^{\circ} \mathrm{C}}{\rightleftharpoons}} 2 \mathrm{NH}_3$
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Question 192 Marks
Give one example each of which illustrates the following characteristics of a chemical reaction change in state
Answer
The reaction between hydrogen sulphide and chlorine $($both gases$)$ produces sulphur $($solid$)$ and hydrogen chloride $($gas$)$.
$\underset{\text { hydrogen sulphide }}{\mathrm{H}_2 \mathrm{~S}(\mathrm{~g})}+\underset{\text { chlorine }}{\mathrm{Cl}_2(\mathrm{~g})} \longrightarrow \underset{\text { hydrogen chloride }}{2 \mathrm{HCl}(\mathrm{gas})}+\underset{\text { sulphur yellow solid }}{\mathrm{S}(\mathrm{s})}$
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Question 202 Marks
Give one example each of which illustrates the following characteristics of a chemical reaction : change of colour
Answer
When blue coloured copper sulphate reacts with hydrogen sulphide gas, a black coloured substance copper sulphide is formed.
$\underset{\text { copper sulphate solution, blue }}{\mathrm{CuSO}_4}+\underset{\text { hydrogen sulphide }}{\mathrm{H}_2 \mathrm{~S}} \longrightarrow \underset{\text { copper sulphide black solid }}{\mathrm{CuS}}+\underset{\text { sulphuric acid }}{\mathrm{H}_2 \mathrm{SO}_4}$
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Question 212 Marks
Give one example each of which illustrates the following characteristics of a chemical reaction : evolution of a gas
Answer
When Zinc reacts with dil. sulphuric acid. Hydrogen gas is evolved, with an effervescence
$\underset{\text { zinc }}{\mathrm{Zn}}+\underset{\text { dil.suphuric acid }}{\mathrm{H}_2 \mathrm{SO}_4} \longrightarrow \underset{\text { zinc sulphate }}{\mathrm{ZnSO}_4}+\underset{\text { hydrogen }}{\mathrm{H}_2}$
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[2 Mark Question Answer] - CHEMISTRY STD 8 Questions - Vidyadip