Interpreting a balanced chemical reaction - class-IX

interpreting a balanced chemical reaction

45 Questions Published

Questions

Question 1 Multiple Choice (Single Answer)

0.05 mole of $LiAlH _4$ in ether solution was placed in a flask containing 74g (1 mole ) of t-butyl alcohol.The product $LiAlHC _{12}H _{27}O _3$ weighed 12.7 g. If Li atoms are conserved, the percentage yield is : (Li=7, Al=27, H=1, C=12, O=16).

  1. 25%
  2. 75%
  3. 100 %
  4. 15 %
Question 2 Multiple Choice (Single Answer)

$1.25$ g of sample of limestone on heating gives $0.44$ g carbon dioxide. The percentage purity of $CaCO _3$ in limestone is:

  1. $75\%$
  2. $85\%$
  3. $90\%$
  4. $80\%$
Question 3 Multiple Choice (Single Answer)

$50\ g$ of an impure calcium carbonate sample decomposes on heating to give carbon dioxide and $22.4\ g$ calcium oxide. The percentage purity of calcium carbonate in the sample is:

  1. $60\%$
  2. $80\%$
  3. $90\%$
  4. $70\%$
Question 4 Multiple Choice (Single Answer)
Statement (A):The constant temperature at which a solid change into liquid state by absorbing heat energy is called melting point.
Statement (B): The constant temperature at which a liquid changes into gaseous state by absorbing heat energy is called point.
Statement (C): The melting and boiling points of a pure substance is always a constant and is a good measure of finding the purity of the substance.
  1. All the statement are correct
  2. All the statement are incorrect
  3. A, B are correct and C is incorrect
  4. A, B are incorrect and C is correct
Question 5 Multiple Choice (Single Answer)

If the percentage yield of the $1 st$ step is $80% $ and that of the $2nd $ step is $75% $, then what is the expected overall percentage yield for producing $CaO _3$ from $CaCl _{2} $?

  1. $50\%$
  2. $70\%$
  3. $55\%$
  4. $60\%$
Question 6 Multiple Choice (Single Answer)

What is the purity of concentrated $H _2SO _4$ solution $(d=1.8gm/mol)$ if $5\text{ ml}$ of these solution is neutralized by $84.5 \text{ ml}$ of $2N \text{ NaOH}$ solution. 

  1. $93 \text {%}$
  2. $94.6 \text {%}$
  3. $92.12 \text {%}$
  4. $91.5 \text {%}$
Question 7 Multiple Choice (Single Answer)

For the reaction, $2Fe(NO _3) _3+3Na _2CO _3\rightarrow Fe _2(CO _3) _3+6NaNO _3$ initially 2.5 mole of $Fe(NO _3) _2$ and 3.6 mole of $Na _2CO _3$ are taken. If 6.3 mole of $NaNO _3$ is obtained then % yield of given reaction is:

  1. 50
  2. 84
  3. 87.5
  4. 100
Question 8 Multiple Choice (Single Answer)

$12.5$ g of an impure sample of limestone on heating gives $4.4$ g of carbon dioxide. The percentage purity of $CaCO _{3}$ in the sample is:

  1. $72$%
  2. $75$%
  3. $80$%
  4. $85$%
Question 9 Multiple Choice (Single Answer)

For the complete reduction of $5.8g$ of acetone to isopropyl alcohol, the quantity of $LiAIH _{4}$ required (assuming chemical yield to be $100%$ ) is approximately [mass:$Li=6.9,Al=27$]

  1. $5.8\ g$
  2. $3.8\ g$
  3. $1.9\ g$
  4. $15.2\ g$
Question 10 Multiple Choice (Single Answer)

0.2828 g of iron wire was dissolved in excess of dilute $H _2SO _4$ and the solution was made upto 100 ml. 20 ml of this solution required 30 ml. of $\dfrac{N}{30} K _2Cr _2O _7$ solution for oxidation. Calculate % purity of iron in the wire:

  1. 99
  2. 95
  3. 90
  4. 85
Question 11 Multiple Choice (Single Answer)

To a $10$ml $1M$ aqueous solution of $Br _2$,excess of NaOH is added so that all $Br _2$ is disproportional to $Br^-$ and $BrO _3^-$, the resulting solution is freed from $Br^-$,by extraction and excess of $OH^-$ neutralised by acidifying the solution. The resulting solution is sufficient the react with $1.5$gm of impure $CaC _2I _4$ $(M=128gm /mol)$ sample. The purity by mass of Oxalate sample is the relevant reaction s are $Br _2(aq.)+OH^- \rightarrow (aq.)+BrO _3^-$
$Bro _3^-+C _2O _4^{2-}\rightarrow Br^-+CO _2$

  1. $85.3\%$
  2. $12.5\%$
  3. $90\%$
  4. $50\%$
Question 12 Multiple Choice (Single Answer)

In the decomposition of 10 g of $Mg{ CO } _{ 3 }$, 0.1 mole ${ CO } _{ 2 }$ and 4.0 g MgO are obtained. Hence, percentage purity of $Mg{ CO } _{ 3 }$ is:

  1. 50%
  2. 60%
  3. 40%
  4. 84%
Question 13 Multiple Choice (Single Answer)

$10g$ of limestone on heating produces $4.2g$ of $CaO$. the percentage purity of $Ca{ CO } _{ 3 }$ in limestone is: 

[Atomic mass of $Ca =$ $40$]

  1. $85%$
  2. $75%$
  3. $95%$
  4. $80%$
Question 14 Multiple Choice (Multiple Answers)

Which of the following is not the criterion of purity of a substance?

  1. Solubility
  2. Melting point
  3. Boiling point
  4. Density
Question 15 Multiple Choice (Single Answer)

Consider the following reaction sequence${ CaCl } _{ 2(aq) }\quad +\quad { CO } _{ 2(g) }\quad +\quad { H } _{ 2 }O\rightarrow { CaCO } _{ 3(s) }\quad +\quad { 2HCl } _{ (aq) }$${ CaCO } _{ 3(s) }\quad \xrightarrow { heat } { CaO } _{ (s) }\quad +\quad { H } _{ 2 }{ O } _{ (g) }$if the percentage yield of the $1st$ step is $80%$ and that of the $2nd$ is $75%$, then what is the expected overall percentage yield producing $CaO$ from ${ CaCl } _{ 2 }$?

  1. $50%$
  2. $70%$
  3. $55%$
  4. $60%$
Question 16 Multiple Choice (Single Answer)

Methyl benzoate is prepared by the reaction between benzoic acid and methanol, according to the equation 
$ C _{ 6 }H _{ 5 }COOH+CH _{ 3 }OH\longrightarrow C _{ 6 }H _{ 5 }COOCH _{ 3 }+H _{ 2 }O$
Benzoic acid     Methanol           Methyl benzoate
In an experiment 24.4 gm of benzoic acid were reacted with 70.0 mL of $ CH _3OH $. The density of $ CH _3OH $ is $ 0.79 g mL^{-1} $. The methyl benzoate produced had a mass of 21.6g. What was the percentage yield of product ?

  1. 91.7%
  2. 79.4%
  3. 71.5%
  4. 21.7%
Question 17 Multiple Choice (Single Answer)

A sample contain $Fe\left (SO _{4}  \right ) _{3},$ $FeSO _{4a}$ and impurities. A 600 g sample contains 48g impurities ans equal moles of $Fe _{2}\left (SO _{4}.  \right )in the % of Fe _{2}\left ( SO _{4} \right ) _{3}$ in the mixture is:

  1. 33.33%
  2. 66.7%
  3. 83.33%
  4. none of these
Question 18 Multiple Choice (Single Answer)

Percentage purity of a sample of gold is $$. How many atoms of gold are present in its $1$ gram
(Atomic mass of gold =$197 u.) 

  1. $2.6*{10^{21}}$
  2. $2.6*{10^{23}}$
  3. $3.0*{10^{21}}$
  4. $4.5*{10^{20}}$
Question 19 Multiple Choice (Single Answer)

For the reaction :

     
$CaO + 2HCl \to CaC{l _2} + {H _2}O$

$2.46 g$ of CaO is reacted with excess of HCl and $3.7 g$ $ CaC{l _2}$ is formed. What is  percentage yield? 

[$Note :  %  Yield = \dfrac{{Actual,yield}}{{Theoretical,yield}} \times 100$] 

  1. 86%
  2. 26%
  3. 76%
  4. 16%
Question 20 Multiple Choice (Single Answer)

$4$ g of hydrogen $(H _2)$, $64$g of sulphur (S) and $44.8$ L of $O _2$ at STP react and form $H _2SO _4$. If $49$g of $H _2SO _4$ is formed, then $%$ yield is  ?

  1. $25\%$
  2. $50\%$
  3. $75\%$
  4. $100\%$
Question 21 Multiple Choice (Single Answer)

With the amounts of reactants provided, it was possible to produce $0.667\ g$ of aspirin. One student produces $0.333\ g$ of aspirin. What was the percent yield for this student's laboratory work?

  1. $40$%
  2. $33$%
  3. $67$%
  4. $50$%
Question 22 Multiple Choice (Single Answer)

A decomposition reaction produces sodium carbonate from sodium bicarbonate.
If the collected mass of sodium carbonate was $3.7\ g$ and the predicted amount was $4.0\ g$, what is the percent yield of the reaction?

  1. $92.5\%$
  2. $95\%$
  3. $7.5\%$
  4. $90\%$
Question 23 Multiple Choice (Single Answer)

A metal oxide (MO) is reduced by heating it in a stream of hydrogen. It is found that after complete reduction, 7.95 g of oxide requires 0.2 g of $H _2$ to yield 6.35 g of the metal. We may deduce that:

  1. The atomic weight of the metal is 48
  2. The atomic weight of the metal is 16
  3. The atomic weight of the metal is 12
  4. The atomic weight of the metal is 63.5
Question 24 Multiple Choice (Single Answer)

20 g of a magnesium carbonate sample decomposes on heating to given carbondioxide, and 8g magnesium oxide. What will be the percentage of purity of ${\text{MgC}}{{\text{O}} _3}$ sample ? 

  1. 96
  2. 60
  3. 84
  4. 75
Question 25 Multiple Choice (Single Answer)

How is percent yield calculated?

  1. $\displaystyle \text { Percent yield } = \dfrac { \text { actual yield } }{ \text { theoretical yield } } \times 100 $
  2. $\displaystyle \text { Percent yield } = \dfrac { \text { actual yield } }{ \text { theoretical yield } \times 100 } $
  3. $\displaystyle \text { Percent yield } = \dfrac { \text { actual yield } }{ \text { theoretical yield } } $
  4. $\displaystyle \text { Percent yield } = \dfrac { \text { theoretical yield } }{ \text { actual yield } } $
  5. $\displaystyle \text { Percent yield } = \text { actual yield } \times \text { theoretical yield } \times 100 $
Question 26 Multiple Choice (Single Answer)

What equation is used to calculate percent yield?
Note: $E=$ experimental; $T=$ theoretical

  1. $\cfrac{E}{T}\times 100$
  2. $\cfrac{(E-T)}{T}\times 100$
  3. $\cfrac{T}{E}\times 100$
  4. $\cfrac{(T-E)}{T}\times 100$
Question 27 Multiple Choice (Single Answer)

$^{14} _6C\rightarrow ^{14} _7N+X$
Water is formed by the addition of 4.0g of $H _2(g)$ to an excess of $O _2(g)$. If 27 g of $H _2O$ is recovered, what is the percent yield for the reaction?

  1. 25%
  2. 50%
  3. 75%
  4. 100%
  5. Cannot be determined
Question 28 Multiple Choice (Single Answer)

Consider the reaction:
$2ZnS + 3O _{2}\rightarrow 2ZnO + 2SO _{2}$
This reaction has an $80.0$ yield.
What mass of $ZnO$ is produced when $50.0\ g\ ZnS$ is heated in an open vessel untill no further weight loss is observed?

  1. $33.4\ g$
  2. $40.4\ g$
  3. $43.4\ g$
  4. $3240\ g$
Question 29 Multiple Choice (Single Answer)

$2Ag{ NO } _{ 3 }+Cu\rightarrow Cu{ \left( { NO } _{ 3 } \right)  } _{ 2 }+2Ag$
What is the percent yield when $0.17\ g$ of $Ag{NO} _{3}$ in aqueous solution reacts with excess copper to produce $0.08\ g$ $Ag$? (At. mass of $Ag=107\ g/mol$) 

  1. $74$%
  2. $47$%
  3. $89$%
  4. $65$%
Question 30 Multiple Choice (Single Answer)

$Zn+{H} _{2}{SO} _{4}\rightarrow Zn{SO} _{4}+{H} _{2}$
A reaction of zinc metal with sulfuric acid produces $1.5\times {10}^{-2}\ mol$ of $Zn{SO} _{4}$ from $2.0\times {10}^{-2}\ mol$ of $Zn$.
What was the percent yield of this reaction?

  1. $25$%
  2. $75$%
  3. $33$%
  4. $67$%
Question 31 Multiple Choice (Single Answer)

$4Co+3{ O } _{ 2 }\rightarrow 2C{ o } _{ 2 }{ O } _{ 3 }$
$66.8\ g$ of Cobalt reacted with oxygen and $70.50\ g$ of $C{ o } _{ 2 }{ O } _{ 3 }$ was collected after the reaction was completed. Calculate the percent yield. (At. mass of $Co=59\ g/mol$)

  1. $75$%
  2. $80$%
  3. $85$%
  4. $90$%
Question 32 Multiple Choice (Single Answer)

A reaction produced $30.0$ grams of carbon dioxide. If the theoretical (expected) yield was $45$ grams, what is the percentage yield?

  1. $15$%
  2. $30$%
  3. $67$%
  4. $150$%
Question 33 Multiple Choice (Single Answer)

When the fertilizer plant completes its small batch process, they find that they have only collected $26\ mL$ of $NH _{3}$ which was supposed to be $100\ mL$. They are disappointed with this result due to the low yield. What is the % yield of their process?

  1. $26$%
  2. $38$%
  3. $52$%
  4. $76$%
Question 34 Multiple Choice (Single Answer)

A reaction is known to have a percent yield of $80$%. It the actual yield is $25$ grams, what was the expected yield?

  1. $3.2\ grams$
  2. $19\ grams$
  3. $31.25\ grams$
  4. $190\ grams$
Question 35 Multiple Choice (Single Answer)

A bacterium can convert xylose to lactic acid with a percent yield of $85$%. What mass of lactic acid would be produced from $50.0\ g$ sample of xylose by this bacterium? (At. mass of xylose$(C _5H _{10}O _5) =150\ g/mol,$ At. of lactic acid$(C _3H _6O _3)=90\ g/mol$).

  1. $58.8\ g$
  2. $85\ g$
  3. $50\ g$
  4. $42.5\ g$
Question 36 Multiple Choice (Single Answer)

A student conducts an experiment to produce a $Ca{CO} _{3}$ precipitate. The student collects $1.80\ g$ of product after predicting it should be possible to produce $2.00\ g$ of the product.
What is the student's percent yield for this experiment?

  1. $-10$%
  2. $+90$%
  3. $+10$%
  4. $+111$%
Question 37 Multiple Choice (Single Answer)

If $100\ mL$ of the acid is neutralised by $100\ mL$ of $4\ M\ NaOH$, the purity of concentrated $HCl$ (sp. gravity $= 1.2)$ is:

  1. $12$%
  2. $98$%
  3. $73$%
  4. $43$%
Question 38 Multiple Choice (Single Answer)

$50\ g$ of a sample of $NaOH$ required for complete neutralisation of $1\ litre\ N\ HCl$. What is the percentage purity of $NaOH$?

  1. $80$
  2. $70$
  3. $60$
  4. $50$
Question 39 Multiple Choice (Single Answer)
In a reaction vessel,100 g $H _2$ and 100 g $Cl _2$ are inbred and suitable conditions are provided for take following reaction: 

$H _2 ( g)+ Cl _2(g)\rightarrow 2HCl(g)$

The amount of $HCI$ formed (at 90% yield) will be:
  1. 36.8 g
  2. 62.5 g
  3. 80 g
  4. 91.98 g
Question 40 Multiple Choice (Single Answer)

In the Haber process:
$N _2(g) + 3H _2(g) \rightarrow 2NH _3(g) $
$30 L$ of $H _2$ and $30 L$ of ${N _2}{^-}$ were taken for reaction which yielded only $50%$ of expected product. What will be the composition of the gaseous mixture in the end?

  1. 20 L $NH _3$, 25 L $N _2$ and 20 L $H _2$
  2. 10 L $NH _3$, 25 L $N _2$ and 15 L $H _2$
  3. 20 L $NH _3$, 10 L $N _2$ and 30 L $H _2$
  4. 20 L $NH _3$, 25 L $N _2$ and 15 L $H _2$
Question 41 Multiple Choice (Single Answer)

$0.5\ g$ of impure ammonium chloride was heated with caustic soda solution to evolve ammonia gas, the gas is absorbed in $150\ mL$ of $N/5\ H _{2}SO _{4}$ solution. Excess sulphuric acid required $20\ mL$ of $1\ N\ NaOH$ for complete neutralization. The percentage of $NH _{3}$ in the ammonium chloride is:

  1. $68$%
  2. $34$%
  3. $48$%
  4. $17$%
Question 42 Multiple Choice (Single Answer)

A sample of $CaCO _3$ is 50% pure. On heating $1.12 L$ of $CO _2$ (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
Question 43 Multiple Choice (Single Answer)

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
Question 44 Multiple Choice (Multiple Answers)

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 $\phi _{gas} << \phi _{solution}$
Question 45 Multiple Choice (Single Answer)

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