Tag: chemistry

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Multiple choice chemistry introduction to analytical chemistry interpreting a balanced chemical reaction percentage yield stoichiometric calculations

In ayurvedic preparation of swarnabhasma, what purity of golden will be used?

  1. $42$ % gold + silver
  2. $91$ % amalgam
  3. $24$ carat
  4. $58.5$% copper
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Swarna Bhasma is prepared from Gold. It is used in Ayurvedic treatment of infertility, asthma, tissue wasting, poisoning etc. This medicine should only be taken strictly under medical supervision.

In the given question option A is the correct answer.

Multiple choice chemistry introduction to analytical chemistry interpreting a balanced chemical reaction percentage yield stoichiometric calculations

One mole of photons is known as one Einstein of radiation. According to Stark-Einstein law of photochemical equivalence, one mole of reactant absorbs one Einstien of energy. For a photochemical reaction, a term called quantum yield is defined as:
Quantum yield $ (\phi) = \dfrac {No. \,of \,moles \,of \,reactant \,converted} {No. \,of \,Einstein \,absorbed} $
The correct statement(s) is/are:

  1. for a chain reaction $\phi _{gas} >> \phi _{solution}$
  2. in a photochemical chain reaction $\phi >> 1$
  3. in a photochemical chain reaction $\phi << 1$
  4. for a chain reaction $\phi _{gas} << \phi _{solution}$
Reveal answer Fill a bubble to check yourself
A,B Correct answer
Explanation
$Quantum \ Yield= \cfrac {Number \ of \ moles \ of \ reactant \ converted}{Number \ of \ einstein \ absorbed}$
An einstein of radiation $=$ one mole of photons
For a chain reaction, $\phi _{gas} >> \phi _{solution}$
and ln photochemical chain reaction $\phi >>1$
Multiple choice chemistry introduction to analytical chemistry interpreting a balanced chemical reaction percentage yield stoichiometric calculations

A sample of $CaC{O _3}$ is $50\% $ pure. On heating $1.12{\text{ }}L$ of $C{O _2}$ (at STP) is obtained. Residue left (assuming non-volatile impurity) is:

  1. 7.8 g

  2. 3.8 g

  3. 2.8 g

  4. 8.9 g
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

No. of moles of $CO _2$ evolved $=\cfrac{1.12}{22.4}=0.05$ $moles$

$CaCO _3(s)\overset { \Delta }{ \longrightarrow } CaO\downarrow+CO _2\uparrow$
                             $0.05$        $0.05$ $moles$
So, $0.05$ $moles$ of $CaCO _3$ have  reacted.
Mass $=0.05\times 100=5$ $gm=50\%$ of $CaCO _3$ sample
Total weight $=2\times 5$ $gm=10$ $gm$
Residue left by $CaCO _3=5$ $gm$
Residue left by $CaO=56\times 0.05=2.8$ $gm$
Toatl residue $=5+2.8=7.8$ $gm$

Multiple choice chemistry acids and alkalis acids with carbonates reactions of acids and bases properties of acids and bases

$Ca(HCO _{3}) _{2} + 2HCl \rightarrow $

  1. $CaCl _{2} + 2H _{2}O + 2CO _{2}$
  2. $2CaCl _{2} + 2H _{2}O + 2CO _{2}$
  3. $CaCl _{2} + 4H _{2}O + 2CO _{2}$
  4. $CaCl _{2} + 2H _{2}O + 4CO _{2}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$Ca(HCO _{3}) _{2} + 2HCl \rightarrow CaCl _{2} + 2H _{2}O + 2CO _{2}$ 

Metal carbonates react with  acids to give salt, carbon dioxide and water.

Multiple choice chemistry acids and alkalis acids with carbonates reactions of acids and bases properties of acids and bases

Acids react with carbonate and bicarbonates to liberate $CO _{2}$.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The metal ion displaces the proton $(H^+)$ from the acid and a salt is formed along with carbonic acid $(H _2CO _3)$

However, $(H _2CO _3)$ is unstable in atmospheric conditions.
$MgCO _3+2HCl\longrightarrow MgCl _2+H _2CO _3$ (Equation $01$)
$H _2CO _3\longrightarrow H _2O+CO _2$ (Equation $02$)
By adding $01$ and $02$
$MgCl _2+2HCl\longrightarrow MgCl _2+H _2O+CO _2$
Similarly,
$Na _2CO _3+H _2SO _4\longrightarrow Na _2SO _4+H _2CO _3$
here, $H _2CO _3$ is split into $H _2O+CO _2$
$ZnCO _3+2HNO _3\longrightarrow Zn(NO _3) _2+H _2O+CO _2$

Multiple choice chemistry acids and alkalis acids with carbonates reactions of acids and bases properties of acids and bases

Choose the correct option to complete the reaction.
$CaCO _{3}(s) + 2HCl(aq) \rightarrow $

  1. $2CaCl _{2}(aq) + H _{2}O(l) + CO _{2}(g)$
  2. $CaCl _{2}(aq) + 3H _{2}O(l) + CO _{2}(g)$
  3. $2CaCl _{2}(aq) + 4H _{2}O(l) + CO _{2}(g)$
  4. $CaCl _{2}(aq) + H _{2}O(l) + CO _{2}(g)$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

$CaCO _{3}(s) + 2HCl(aq) \rightarrow CaCl _{2}(aq) + H _{2}O(l) + CO _{2}(g)$ 

All metal carbonates and hydrogen carbonates react with acids to gives corresponding salt, carbon dioxide and water.

Multiple choice chemistry acids and alkalis acids with carbonates reactions of acids and bases properties of acids and bases

$2HCl{(aq)} + MgCO _{3}(s)\rightarrow$

  1. $MgCl _{2}(aq) + CO _{2}(g) + H _{2}O(l)$
  2. $MgCl _{2}(aq) + CO _{2}(g)$
  3. $MgCl _{2}(aq) + H _{2}O(l)$
  4. $MgCl _{2}(aq) + CO _{2}(g) + 3H _{2}O(l)$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$(A)$  $MgCl _{2}(aq)$ + $CO _{2}(g)$ + $H _{2}O(l)$


$Reaction$ : $2HCl(aq)$ + $MgCO _{3}(s)$ $\rightarrow$ $MgCl _{2}(aq)$ + $CO _{2}(g)$ + $H _{2}O(l)$