The burning of magnesium in the air conducts that reaction where magnesium and oxygen combine to form magnesium oxide. As two elements combine each other, it is called a combination reaction.
2Mg + O2 ------> 2MgO
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a. Reactants and products.
| Reactants | Products |
| The chemicals that undergo chemical changes are reactants. | The chemicals that are formed as a result of the reaction are products. |
| These are the chemicals before the reaction between them occurs. | These are the chemicals after the reaction between them occurs. |
b. Word equation and formulae equation.
| Word | Formulae |
| It is the representation of chemical equations by words. | It is the representation of chemical equations by symbols. |
| It is less informative. | It is more informative. |
| It is longer and non-convenient. | It is shorter and convenient. |
c. Combination reaction and decomposition reaction.
| Combination | Decomposition |
| In this reaction, different reactants are combined to form a single product. | In this reaction, a single reactant is decomposed to form multiple products. |
| It occurs either in the presence or absence of heat. | It occurs in the presence of heat only. |
d. Positive catalyst and negative catalyst.
| Positive | Negative |
| It increases the rate of a chemical reaction. | It decreases the rate of a chemical reaction. |
| It is used to accelerate the reaction. | It is used to slow down the reaction. |
| Mn02 is an example. | Glycerine is an example. |
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We know, lanthanides are rare earth metals, and actinides are radioactive metals. The properties of lanthanides resemble each other very closely but are different from the rest elements due to the preferential filling of f-orbitals. So, they are placed separately to avoid unnecessary sidewise expansion of the periodic table.
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The atomic weight of an element expressed in grams is called gram atomic weight.
The molecular weight of a substance expressed in grams is called molecular weight.
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For an equipotential surface,
Change in potential difference, ∆V = 0
Work done = q×∆V = q×0 = 0
Also,
Work done = Fs cosA = 0
Where, F = Force due to charges,
s = distance between charged bodies, and
A = angled between direction of F and s
Since, the equipotential surface is formed due to cancellation of equal and opposite electric fields, F and s cannot be 0.
So, Work done = 0 if and only if cos A = 0 → A = 90°
Hence, the equipotential surfaces are always at right angles to lines of electric force.
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In terms of Classical idea:
Oxidation: Addition of oxygen or any other electronegative element to a substance .Conversely , Removal of Hydrogen or any other electropositive element from a substance.
Mg (s) + S (s) ➡MgS (s)
Similarly, Reduction is just opposite process of oxidation.
2FeCl3(aq) + H2(g)➡2FeCl2(aq) + 2HCl (aq)
In terms of Electron transfer reaction:
Oxidation: Loss of electron
Reduction: Gain of electron
Oxidant: Acceptor of electron
Reductant: Donor of electron
- Oxidation number simply denotes the oxdiation state of an element in a compound.
- It is mainly based on basis that electron pair in a covalent bond belongs to entirely to more electronegative element.
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