Tag: basic concepts of chemistry

Questions Related to basic concepts of chemistry

Carbon and oxygen form two compounds. Carbon content in one of them is $42.9$% and in the other is $27.3$%. The given data is in agreement with:

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

  1. law of conservation of mass

  2. law of multiple proportions

  3. law of reciprocal proportions

  4. law of definite proportions

Show answer
Correct Option: B
Explanation:

The given data is in agreement with Law of multiple proportions.

The Law of multiple proportions states that the masses of one element combine with a fixed mass of the second element are in a ratio of whole numbers.
In $100$ $g$ of the first compound $O:C=$$57$ $/42.9$ $=1.33$  
In $100$ $g$ of the second compound $O:C=$$72.7$ $/27.3$ $=2.66$  
Ratio $=2.66:1.33=2:1$
This whole number ratio is consistent with Law of multiple proportions. 

$12g$ of carbon combines with $64g$ sulphur to form ${CS} _{2}$. $12g$ carbon also combines with $32g$ oxygen to form ${CO} _{2}$. $10g$ sulphur combines with $10g$ oxygen to form ${SO} _{2}$. These data illustrate the

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

  1. Law of multiple proportions

  2. Law of definite proportions

  3. Law of reciprocal proportions

  4. Law of gaseous volumes

Show answer
Correct Option: C
Explanation:

Given,

$12g$ $C$ combines with $64g$ $S$ to give $CS _2$
$12g$ $C$ combines with $32g$ $O$ to give $CO _2$
Also, $10gS$ combines with $10gO$ to give $SO _2$
In $CS _2$ $C:S=12:64=3:16$
In $CO _2$ $C:O=12:32=3:8$
From, $CS _2$ & $CO _2$, $S:O=16:8=2:1$
Also in $SO _2$ $S:O=10:10=1:1$
$\Rightarrow 2:1$ is multiple of $1:1$
$\cfrac {1}{1}\times 2=\cfrac {2}{1}$
$\Rightarrow $ Law of reciprocal proportions is illustrated here.

A chemical equation is balanced according to 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. conservation of mass

Show answer
Correct Option: D
Explanation:
When we balance an equation, we determine the ratio of reactants to products which allows for the total number of atoms of reactants to match the number of atoms of the products.

 Since the type of atoms does not change and the number of atoms stays that same, the total mass that goes into the chemical change will match the mass that comes out after the change.

   So, law of conservation of mass is the correct answer.

Carbon and oxygen from two compounds. Carbon content in one of them is 42.9% and in the other is 27.3%. The given data is in agreement with :

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

  1. law of conservation of mass

  2. law of multiple proportions

  3. law of reciprocal proportions

  4. law of definite proportions.

Show answer
Correct Option: B

Law of multiple proportions is illustrated by which one of the  following pairs ?

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

  1. $H _{2}S$ and $SO _{2}$

  2. $NH _{3}$ and $NO _{2}$

  3. $N _{2}O$ and NO

  4. $N _{2}S$ and $Na _{2}O$

Show answer
Correct Option: C
Explanation:
Law of multiple proportions say that if 2 elements form more than one compounds 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.
In $N _{2}O$ and $NO$, the ratio of weight of $N$ reacting with a constant weight of $O$ is $2:1$

State True or False.
If two elements can combine to form more than one compound, the masses of one element that combine with a fixed mass of the other element, are in whole number ratio.

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

  1. True

  2. False

Show answer
Correct Option: A
Explanation:

When two elements can combine to form more than one compound, the masses of one element that combine with a fixed mass of the other element, are in whole number ratio. This is the law of multiple proportions.
Consider two elements $C$ and $O$. They combine to form $CO$ and $CO _2$.
The masses of oxygen that combine with $12$ g of carbon to form $CO$ and $CO _2$ are $16$ g and $32$ g respectively. They are in whole number ratio $1:2$.

$P _xO _y$ what will be correct value of $x$ and $y$ if $P$ and $H$ combine in the mass ratio of $3.1 : 0.3$ and in water $H$ and $O$ combine in the mass ratio $0.2 : 1.6$?

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

  1. $1$ and $1$

  2. $1$ and $2$

  3. $2$ and $3$

  4. $2$ and $5$

Show answer
Correct Option: C
Explanation:

 

$P:H = 3.1 : 0.3 = (3.1 \times : 0.30) \times 2 = 6.2 : 0.6$

$H:O = 0.2 : 1.6 = (0.2 \times 3 : 1.6) \times 3 = 0.6 : 4.8$

$P:O = 6.2 : 4.8 = 3.1 : 2.4 $ (ratio by mass) $= 1.29: 1$

$1.29$ mass $P= 1 $ mass $O$

$x$ mass $P= 16 \ g$ mass $O$

$x= 16 \times 1.29 = 20.64 \ g$ Phosphorous

$= \cfrac {20.64}{31}$ moles Phosphorous

$= 0.66$

$1 \ mole \ O(y) = 0.66 \ mole \ P(x) = \cfrac 23$

$\therefore \ x:y = 2:3 $

$x =2 \ ; \ y=3$

The standard temperature is:

chemistry basic concepts of chemistry measurement of properties effect of temperature and pressure on states of matter general introduction: importance and scope of chemistry

  1. $273^0C$

  2. $273K$

  3. $-273K$

  4. $23K$

Show answer
Correct Option: B
Explanation:

The standard temperature is considered to be $273K$

i.e. $0°C$

The S.I unit of atmospheric pressure is :

chemistry basic concepts of chemistry measurement of properties effect of temperature and pressure on states of matter general introduction: importance and scope of chemistry

  1. $L\ atm$

  2. $N/m$

  3. $Pascal$

  4. None of these

Show answer
Correct Option: C
Explanation:

The S.I unit of atmospheric pressure is $N/m^2$ or $Pascal$.

           $1\quad Pascal =1N/m^2$
           $1\quad atm =101325\quad Pascal$
           $1\quad bar =10^5\quad Pascal$

What is the SI unit of mass? 

chemistry basic concepts of chemistry measurement of properties effect of temperature and pressure on states of matter general introduction: importance and scope of chemistry

  1. kg

  2. LBS

  3. Pounds

  4. None of these

Show answer
Correct Option: A
Explanation:

  • SI unit definition is a unit of measurement that is a universally accepted system used for scientific and technical work all over the world.
  • The kilogram is the SI base unit of mass and is equal to the mass of the international prototype of the kilogram, a platinum-iridium standard that is kept at the International Bureau of Weights and Measures (BIPM).