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Posted by Divyanshi Dhakad 5 years, 1 month ago
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Meghna Thapar 5 years, 1 month ago
Scientific evidence shows that the physical and behavioral traits shared by all people originated from apelike ancestors and evolved over a period of approximately six million years. One of the earliest defining human traits, bipedalism -- the ability to walk on two legs -- evolved over 4 million years ago. On the biggest steps in early human evolution scientists are in agreement. The first human ancestors appeared between five million and seven million years ago, probably when some apelike creatures in Africa began to walk habitually on two legs. They were flaking crude stone tools by 2.5 million years ago.
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Chemical reactions can be classified in following types:
- Combination Reaction
- Decomposition Reaction
- Displacement Reaction
- Double Displacement Reaction
- Oxidation and Reduction Reaction
Combination Reaction: Reactions in which two or more reactants combine to form one product are called COMBINATION REACTION.
A general combination reaction can be represented by the chemical equation given here.
<i>A + B ⇨ AB</i>
<hr />Example: When magnesium is burnt in air (oxygen), magnesium oxide is formed. In this reaction, magnesium is combined with oxygen.
<i>Mg + O2 ⇨ 2MgO</i>
<i>Magnesium + Oxygen ⇨ Magnesium oxide</i>
When carbon is burnt in oxygen (air), carbon dioxide is formed. In this reaction, carbon is combined with oxygen.
<i>C + O2 ⇨ CO2</i>
<i>Carbon + Oxygen ⇨ Carbon dioxide</i>
When hydrogen reacts with chlorine, hydrogen chloride is formed.
<i>H2 + Cl2 ⇨ 2HCl</i>
<i>Hydrogen + Chlorine ⇨ Hydrogen chloride</i>
When calcium oxide reacts with water, calcium hydroxide is formed
<i>CaO + H2O ⇨ Ca(OH)2</i>
<i>Calcium oxide + Water ⇨ Calcium hydroxide</i>
When carbon monoxide reacts with oxygen, carbon dioxide is formed.
<i>2CO + O2 ⇨ 2CO2</i>
<i>Carbon monoxide + Oxygen ⇨ Carbon dioxide</i>
<hr />Decomposition Reaction: Reactions in which one compound decomposes in two or more compounds or element are known as DECOMPOSITION REACTION. Decomposition reaction is just opposite of combination reaction.
A general decomposition reaction can be represented as follows:
<i>AB ⇨ A + B</i>
Example: When calcium carbonate is heated, it decomposes into calcium oxide and carbon dioxide
<i>CaCO3 ⇨ CaO + CO2</i>
<i>Calcium carbonate ⇨ Calcium oxide + Carbon dioxide</i>
When ferric hydroxide is heated, it decomposes into ferric oxide and water
<i>2Fe(OH)3 ⇨ Fe2O3 + 3H2O</i>
<i>Ferric hydroxide ⇨ Ferric oxide + Water</i>
When lead nitrate is heated, it decomposes into lead oxide, nitrogen dioxide and oxygen.
<i>2Pb(NO3)2 ⇨ 2PbO + 4NO2 + O2</i>
<i>Lead nitrate ⇨ Lead oxide + Nitrogen oxide + Oxygen</i>
In above examples, compound is decomposed because of heating, so, these reactions are called THERMAL DECOMPOSITION REACTION.
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Gaurav Seth 5 years, 1 month ago
The human excretory system comprises of the following structures: two bean-shaped kidneys, two ureters, one urinary bladder, and one urethra.
Kidneys are the main organ of the human excretory system. The kidneys are paired organs and are located one on each side of the spine at the level of the liver. They are divided into three regions- the renal cortex which is the outer layer, the renal medulla which is the inner layer and the renal pelvis which is responsible for carrying the urine from the kidney to the ureter. The functional unit of a kidney is called the nephron.
There is one ureter that comes out of each kidney as an extension of the renal pelvis. The ureter is a thin muscular tube that carries urine from the kidneys to the bladder.
The bladder receives urine from the ureters, one from each kidney. It is a sac-like structure that is lined with smooth muscle layer and is responsible for storage of urine till it is expelled from the body by micturition (urination).
The urethra is a tube that arises from the urinary bladder and expels urine by micturition. The urethra is shorter in females and longer in the males. In males, the urethra functions as a common path for sperms and urine. The opening of the urethra is guarded by a sphincter that is voluntary.
Posted by Anjali Kushwaha 5 years, 1 month ago
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Rakshit Sharma 5 years, 1 month ago
Gaurav Seth 5 years, 1 month ago
Its due to Total internal reflection (TIR) . When the light rays enter diamond it acts as a prism and disperses the light in its seven constituent colours and after when these colours strike the others surface of diamond TIR takes place and then after emerging the white light again combines into white light and we see the diamonds as if they are sparkling
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Gaurav Seth 5 years, 1 month ago
Resistance is the property of a conductor, which determines the quantity of current that passes through it when a potential difference is applied across it.
A resistor is a electrical componet with a predetermined electrical resistance, like 1 ohm, 10 ohms 100 ohms 10000 ohms etc.
Depending on how much current you want to pass through a circuit, you would design the circuit with the required resistors.
When it comes actual circuit designing, dealing with components or physical board designing, these two words become interchangeable.For example, if we say "a resistor of 22 ohms" or we say "a resistance of 22 ohms", both are accpetable.
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Gaurav Seth 5 years, 1 month ago
ANSWER
Na is the most electropositive element because as we move left to right in a period electropositivity decreases.
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Hydrogenation is the chemical reaction between hydrogen and other compounds in the presence of catalyst. . Hydrogenation is an addition reaction.
Industrial application: Hydrogenation is used in many industrial applications.
For example; in Petrochemical Industry, hydrogenation is used to convert alkenes into alkanes (paraffins) and cycloalkanes. Hydrogenation is also used to prepare vegetable ghee from vegetable oils.
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Gaurav Seth 5 years, 1 month ago
(i) The controversy over the Hindi and English as the official language started when our Constitution made the provision that the use of English for official purposes was to stop in 1965.
(ii) However, many non-Hindi speaking states demanded that the use of English should continue. In Tamil Nadu, this movement took a violent form.
(iii) So the central government responded by agreeing to continue the use of English along with Hindi for official purposes.
(iv) Thus, the flexibility shown by Indian political leaders helped our country to avoid the tense situation like that in Sri Lanka.
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King?Adithya H. M.. 5 years, 1 month ago
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