ChemistryQ1–6 of 6 questions
Page 1 of 1 · English
1
ChemistryEasyMCQIIT JEE · 1978
$A$ chemical reaction is at equilibrium when
A
Reactants are completely transformed into products
B
The rates of forward and backward reactions are equal
C
Formation of products is minimised
D
Equal amounts of reactants and products are present
Solution
(B) If the rate of forward reaction equals the rate of backward reaction,then the reaction is said to be in equilibrium. At this stage,there is no further change in the concentrations of reactants as well as products.
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2
ChemistryEasyMCQIIT JEE · 1978
The reaction $A + B \rightleftharpoons C + D + \text{heat}$ has reached equilibrium. The reaction may be made to proceed forward by:
A
Adding more $C$
B
Adding more $D$
C
Decreasing the temperature
D
Increasing the temperature
Solution
(C) The given reaction is $A + B \rightleftharpoons C + D + \text{heat}$.
Since heat is released as a product,the reaction is exothermic.
According to Le Chatelier's principle,for an exothermic reaction,decreasing the temperature shifts the equilibrium in the forward direction to produce more heat.
Since heat is released as a product,the reaction is exothermic.
According to Le Chatelier's principle,for an exothermic reaction,decreasing the temperature shifts the equilibrium in the forward direction to produce more heat.
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3
ChemistryEasyMCQIIT JEE · 1978
The composition formula of gypsum is
A
$(CaSO_4)_2 \cdot H_2O$
B
$2CaSO_4$
C
$CaSO_4 \cdot 2H_2O$
D
$2CaSO_4 \cdot H_2O$
Solution
(C) Gypsum is a naturally occurring mineral composed of calcium sulfate dihydrate.
Its chemical formula is $CaSO_4 \cdot 2H_2O$.
Its chemical formula is $CaSO_4 \cdot 2H_2O$.
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4
ChemistryMediumMCQIIT JEE · 1978
$A$ black sulphide is formed by the action of $H_2S$ on
A
Cupric chloride
B
Cadmium chloride
C
Zinc chloride
D
Sodium chloride
Solution
(A) The reaction of $H_2S$ with metal salts leads to the formation of metal sulphides.
$CuCl_2 + H_2S \to CuS \text{ (Black ppt.)} + 2HCl$.
$CdCl_2 + H_2S \to CdS \text{ (Yellow ppt.)} + 2HCl$.
$ZnCl_2 + H_2S \to ZnS \text{ (White ppt.)} + 2HCl$.
$NaCl$ does not react with $H_2S$ to form a sulphide precipitate.
Therefore,the correct option is $A$.
$CuCl_2 + H_2S \to CuS \text{ (Black ppt.)} + 2HCl$.
$CdCl_2 + H_2S \to CdS \text{ (Yellow ppt.)} + 2HCl$.
$ZnCl_2 + H_2S \to ZnS \text{ (White ppt.)} + 2HCl$.
$NaCl$ does not react with $H_2S$ to form a sulphide precipitate.
Therefore,the correct option is $A$.
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5
ChemistryMediumMCQIIT JEE · 1978
Copper can be extracted from
A
Kupfernickel
B
Dolomite
C
Galena
D
Malachite
Solution
(D) is the correct answer. Malachite is a carbonate ore of copper with the chemical formula $Cu(OH)_2 \cdot CuCO_3$. It is a significant source for the extraction of copper.
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6
ChemistryEasyMCQIIT JEE · 1978
The metallurgical process in which a metal is obtained in a fused state is called:
A
Smelting
B
Roasting
C
Calcination
D
Froth floatation
Solution
(A) The process of extraction of a metal in its molten (fused) state by using a reducing agent in the presence of a flux is called $Smelting$.
For example,oxides of less electropositive metals like $Pb$,$Zn$,$Fe$,and $Cu$ are reduced by carbon or other reducing agents at high temperatures to obtain the metal in a fused state.
For example,oxides of less electropositive metals like $Pb$,$Zn$,$Fe$,and $Cu$ are reduced by carbon or other reducing agents at high temperatures to obtain the metal in a fused state.
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