Tag: basic concepts of chemistry

Questions Related to basic concepts of chemistry

$CaCO _3 + 2HCl \rightarrow CaCl _2 + H _2O + CO _2$

The mass of calcium chloride formed when 2.5 g of calcium carbonate is dissolved in excess of hydrochloric acid is:

chemistry basic concepts of chemistry law of multiple proportion law of multiple proportions laws of chemical combination

  1. 1.39 g

  2. 2.78 g

  3. 5.18 g

  4. 17.8 g

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Correct Option: B
Explanation:

CaCO3 + 2HCl -----> CaCl2 + H2O + CO2. 
2.5g? g 
Mass of CaCO3= 40+12+3(16)=52+ 48= 100. 
Molar mass of CaCO3=100g. 
Mass of CaCl2= 40 + 2(35.5)= 40+ 71= 111. 
Molar mass of CaCl2=111g. 
Mass of CaCO3 (g) Mass of CaCl2 (g) 
For 100g of $CaCO _3$, 111g of CaCl_2$ is formed.
let for 2.5g of $CaCO_3$, $x$ g of $CaCl_2$ is formed.
Thus, by cross multiplication,

$x=111\times 2.5/100= 2.775g = 2.78g$.

For describing law of multiple proportions, which among the following pair can be used?

chemistry basic concepts of chemistry law of multiple proportion law of multiple proportions laws of chemical combination

  1. NO and $NO _2$

  2. $CH _4$ and $CO _2$

  3. $ZnO _2$ and $ZnCl _2$

  4. $NH _3$ and $NH _4Cl$

  5. $H _2O$ and HCl

Show answer
Correct Option: A
Explanation:

For describing law of multiple proportions, the pair $\displaystyle  NO$ and $\displaystyle  NO _2$ can be used.
According to the law of multiple proportions, if two elements combine to form more than one compound, then the different masses of one element which combine with fixed mass of other element, bear a simple ratio to one another.
In the pair $\displaystyle  NO$ and $\displaystyle  NO _2$, we have two elements N and O that combine to form more than one compound. In all other examples, more than two elements are present.

A metal forms two oxides with first oxide having 1 and second having 3 oxygen atoms and their masses are 74g and 164 g respectively. If the gram atomic mass of oxygen is 16g, do both compounds follow the law of multiple proportions?

chemistry basic concepts of chemistry law of multiple proportion law of multiple proportions laws of chemical combination

  1. True

  2. False

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Correct Option: A

The law of the multiple proportion was proposed by:

chemistry basic concepts of chemistry law of multiple proportion law of multiple proportions laws of chemical combination

  1. Dalton

  2. Dulong

  3. Petit

  4. Lavoisier

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Correct Option: A
Explanation:

The law of the multiple proportion was proposed by Dalton.
Law of multiple proportions, statement that when two elements combine with each other to form more than one compound, the weights of one element that combine with a fixed weight of the other are in a ratio of small whole numbers.

Hydrogen and oxygen forms two compounds. The hydrogen content in these compounds is 42.9% and 27.3%. These compounds follow which law ?

chemistry basic concepts of chemistry law of multiple proportion law of multiple proportions laws of chemical combination

  1. Law of definite proportion

  2. Law of reciprocal proportion

  3. Law of multiple proportion

  4. Law of combining volumes

Show answer
Correct Option: C
Explanation:

The law of multiple proportions state that if two elements form more than one compound between them then the ratios of the masses of the second element which combine with a fixed mass of the first element will be ratios of small whole numbers.

The chloride of a solid metallic element contains 57.89% by mass of the element. The specific heat of the element is $0.0324\, cal\, deg^{-1}\, g^{-1}$. Calculate the exact atomic mass of the clement. 

chemistry basic concepts of chemistry law of multiple proportion law of multiple proportions laws of chemical combination

  1. 195.2

  2. 195

  3. 195.9

  4. 194

Show answer
Correct Option: A
Explanation:
% of element is given in this question = 57.89
so %  of chlorine is = 100-57.89 = 42.11

Equivalent wt of metal= $\dfrac{57.89}{42.11} \times 35.5$ = 48.8

specific heat of metal= 0.0324

$\rightarrow $ According to Dulong and Petit's law
Approx atomic wt of metal= $\dfrac{6.4}{ specific heat} = \dfrac{6.4}{0.0324}$ = 197.53

Valency of metal= Approximate atomic wt/ Equivalent wt

 = $\dfrac{197.53}{ 48.8}$ = 4.04  = 4

Exact atomic wt of metal = $ Equivalent wt of metal\times Valency of metal$ = 48.8 x 4
  = 195.2
answer is A

Two different oxides of manganese are compared in the table shown below.

Color % Mn (by mass) % O (by mass)
Oxide # $1$ Black $63.19$ $36.81$
Oxide # $2$ Dk Green $77.50$ $22.50$

When substituted for X and Y in the fraction below, which pair CORRECTLY gives a result that illustrates the Law of Multiple Proportions?
$63.19$
$\overline {X}$
$\overline {77.50}$
$\overline {Y}$

chemistry basic concepts of chemistry law of multiple proportion law of multiple proportions laws of chemical combination

  1. $X = 54.94$

    $Y = 54.94$

  2. $X = 36.81$

    $Y = 22.50$

  3. $X = 16.00$

    $Y = 16.00$

  4. $X = 22.50$

    $Y = 36.81$

Show answer
Correct Option: A

Which of the following pairs illustrates the law of multiple proportions?

chemistry basic concepts of chemistry law of multiple proportion law of multiple proportions laws of chemical combination

  1. $PH _3$, $HCl$

  2. $PbO$, $PbO _2$

  3. $H _2S$, $SO _2$

  4. $CuCl _2$, $CuSO _4$

Show answer
Correct Option: B
Explanation:

the law of multiple proportions.: two elements combine to form more than one compound and the masses of one element that combine with a fixed mass of the other element is in the ratio of small whole numbers. 

So all elements are same only the mass ratio of reactants varies the product formation.
thus in $PbO$ and $PbO _2$ the reactants are $Pb$ and $O _2$ that combine in different ratio. other options do not have all the elements common.
option B is correct

Which of the following statements illustrates the law of multiple proportions?

chemistry basic concepts of chemistry law of multiple proportion law of multiple proportions laws of chemical combination

  1. An element forms two oxides, XO and $XO _2$ containing $50\%$ and $60\%$ oxygen respectively. The ratio of masses of oxygen which combines with 1 g of element is 2:3

  2. Hydrogen sulphide contains $5.89\%$ hydrogen, water contains $11.1\%$ hydrogen and sulphur dioxide contains $50\%$ oxygen.

  3. 3.47 g of $BaCl _2$ reacts with 2.36 g of $Na _2SO _4$ to give 3.88 g of $BaSO _4$ and 1.95 g of NaCl.

  4. 20 mL of ammonia gives 10 volumes of $N _2$ and 30 volumes of $H _2$ at constant temperature and pressure

Show answer
Correct Option: A
Explanation:
Law of multiple proportions states that when two elements combine to form two or more compounds, the masses of one element which combine with the fixed mass of another element, will always be in ratio of whole numbers.
The statement is :
An element forms two oxides $XO$ and ${ XO } _{ 2 }$ containing $50$% and $60$% of oxygen respectively. The ratio of masses of ${ O } _{ 2 }$ which combine with $1g$ of element of $2:3$.

In compound A, 1.0 g nitrogen combines with 0.57 g oxygen. In compound B, 2.0 g nitrogen unite with 2.24 g oxygen and in compound C, 3.0 g nitrogen combine with 5.11 g oxygen. These results obey the law of: 

chemistry basic concepts of chemistry law of multiple proportion law of multiple proportions laws of chemical combination

  1. multiple proportions

  2. constant proportions

  3. reciprocal proportions

  4. none of these

Show answer
Correct Option: A
Explanation:

In compound A 1 gm of nitrogen combined with 0.57 gm of oxygen and compound B 1 gm of nitrogen combined with 1.12 gm of oxygen and C 1 gm of nitrogen combined with 1.7 gm of oxygen so the fixed amount of nitrogen is 1: 2 :3 so this follows of multiple proportion rule