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1. A metal oxide contains 34.78% of oxygen. The vapour density of metal chloride is 75.75. The atomic weight of metal is:
2. The relative atomic mass of chlorine is 35.5. A sample of chlorine is a mixture of Cl-35 and Cl-37. What are relative percentage of two isotopes of chlorine?
3. Calculate total number of mole in a reaction mixture of 4 gm of `H_2` and 48 gm of `O_2`.
4. When treated with dilute HCl, 0.3 g of magnesium liberate 290 ml of hydrogen at NTP. Calculate equivalent weight of Magnesium.
5. Calculate mass of an atom of Sulphur.
6. Calculate number of electrons present in 1.8 gm of `H_2O`.
7. Explain equivalent weight.
Equivalent weight is the combining weight of the species.
Equivalent weight= Atomic weight / Valency
Equivalent weight of acid= Molecular weight / Basicity
The basicity of an acid is the number of replaceable H atom.
| Acid | Basicity | Eqv.Wt. |
| `HNO_3` | 1 | 63 |
| `HCl` | 1 | 36.5 |
| `H_2SO_4` | 2 | 49 |
| `H_3PO_4` | 3 | 32.66 |
| `HCOOH` | 1 | 46 |
| `C_2H_2O_4` | 2 | 45 |
Some Exceptions:
- The basicity of hypophosphorous acid (`H_3PO_2`) is 1.
- The basicity of Phosphorous acid (`H_3PO_3`) is 2.
- In reaction `CO_2+2NaOH-->Na_2CO_3 + H_2O` the basicity of `CO_2` is 2.
- In reaction `N_2O_5+2NaOH-->2NaNO_3+H_2O` the basicity of `N_2O_5` is 2
- In reaction `P_2O_5+6NaOH-->2Na_3PO_4+3H_2O` the basicity of `P_2O_5` is 6.
The equivalent weight of base = Molecular weight / Acidity
The acidity of a base is the number of `OH^-` ion or twice the `O^- -` ion present in the base.
| Base | Acidity | Eqv. Wt. | |
| `NaOH` | 1 | 40 | |
| `KOH` | 1 | 56 | |
| `CaO` | 2 | 28 | |
| `Fe_2O_3` | 6 | 26.66 | |
| `Ca(OH)_2` | 2 | 37 |
Equivalent weight of salt=( Molecular weight of salt ) / (Total number of positive charges cations or negative charges on anions)
Equivalent weight can be determined by following methods:
- By hydrogen displacement method
- By oxide formation method
- By double displacement method
By hydrogen displacement method:
This method is used for metals that can displace `H_2` gas from acids.
`Equival ent\ weight\ of m e tal = (wt. of me ta l)/(wt.\ of\ H_2\ displ aced)**1.008`
`=(wt. of me ta l)/(wt.\ of\ H_2\ displ aced\ at\ STP \ ( l))**11.2`
By oxide formation method:
`Equival ent\ weight\ of\ e l ement = (wt. of\ el ement)/(wt.\ of\ o xyg e n)**8`
By double displacement method:
The equivalent weight is calculated from the weight of the compounds using the reactions.
`(Eq. weight\ of\ AB)/(Eq. weight\ of\ CD)=(weight\ of\ AB)/( weight\ of\ AB)`
8. 4.2 g of metal carbonate on heating gave 1.12 l of `CO_2` gas at STP. Calculate equivalent weight of metal.
9. Calculate total number of atoms present in 2.8 l of ethane gas at STP?
10. Explain molecular weight of an element.
Molecular weight of a substance is the relative weight which is the number of times a molecule of a substance is heavier than `1/12` of an atom of C-12.
It is the algebraic sum of atomic weight.
Molecular weight can be determined by following three methods:
- By diffusion method
- By vapour density method
- By avogadros method
By diffusion method:
This method is based on Grahams law of diffusion and is applicable only for gases.
`r_1/r_2=root()(M_2/M_1)`
Where r represents the rate of diffusion.
If equal volume of gas have diffused, then
`t_1/t_2=root()(M_2/M_1)`
By vapour density method:
Molecular weight of unknown gas=Vapour density * molecular weight of reference gas.
If reference gas is not specified then it is assumed to be Hydrogen.
By avogadros method:
Molecular weight=2 * V.D
where, V.D=Density of gas/ (Density of `H_2` gas under same temperature and pressure)
Under same temperature and pressure, equal volume of any gas contains same number of molecules or moles.
All Chapters
Chemical Arithmetic
Volumetric Analysis
Ionic Equilibrium
Language Of Chemistry
Introduction to Metallurgy
Alkali Metals and their Compounds
Copper and Its Compounds
Zinc
Iron
Chemical Bond
- Electronic Theory of valency
- Types and properties of Chemical Bond
- Lewis Dot Structures and Octet rule
- Polar and non polar bonds
- Dipole Moment
- Fajans Rule
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Radioactivity
State of Matter-Solid,Liquid and gaseous state
Chemical Airthmetics Model Exam
Atomic Structure Model Exam
Periodic Table Model Exam
The Chemical Bond
OXIDATION AND REDUCTION
Electro-Chemistry
CHEMICAl KNEMATICS
Chemistry Basic Concepts
Structure of Atom
Classification of Elements and Periodicity in Properties
Chemical Bonding and Molecular Structure
States of Matter
Thermodynamics
Equilibrium
Redox Reactions
Hydrogen
s-Block Elements
p-Block Elements
Organic Chemistry – Basic Principles and Technique
Hydrocarbons
Environmental Chemistry
Solid State
Solutions
Electrochemistry
Chemical Kinetics
Surface Chemistry
General Principles and Processes of Isolation of Elements
P-Block Elements
D and F-Block Elements
Coordination Compounds
Haloalkanes and Haloarenes
Alcohols, Phenols and Ethers
Aldehydes, Ketones and Carboxylic Acids
Amines
Biomolecules
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Chemistry in Everyday Life
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IIT Competitive exams MCQ of chemistry
A metal oxide contains 34.78% of oxygen. The vapour density of metal chloride is 75.75. The atomic weight of metal is:
The relative atomic mass of chlorine is 35.5. A sample of chlorine is a mixture of Cl-35 and Cl-37. What are relative percentage of two isotopes of chlorine?
Calculate total number of mole in a reaction mixture of 4 gm of `H_2` and 48 gm of `O_2`.
When treated with dilute HCl, 0.3 g of magnesium liberate 290 ml of hydrogen at NTP. Calculate equivalent weight of Magnesium.
Calculate mass of an atom of Sulphur.
Calculate number of electrons present in 1.8 gm of `H_2O`.
Explain equivalent weight.
4.2 g of metal carbonate on heating gave 1.12 l of `CO_2` gas at STP. Calculate equivalent weight of metal.
Calculate total number of atoms present in 2.8 l of ethane gas at STP?
