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Atoms And Molecules
What is the present accepted or IUPAC (International Union of Pure and Applied Chemistry) system of symbols of elements?
Many of the symbols are the first one or two letters of the element’s name in English. The first letter of a symbol is always written as a capital letter (upper case) and the second letter as a small letter (lower case). For example, Hydrogen is written as H and Aluminium is written as Al.
Some symbols are formed from the first letter of the name and a letter, appearing later in the name. Examples : Chlorine, Cl and Zinc, Zn.
Some other symbols are taken from the names of elements in Latin, German or Greek. For example, the symbol of iron is Fe from Latin name ferrum.
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Calculate the number of molecules of sulphur (S8) present in 16 gm of solid sulphur.
Calculate the number of aluminium ions present in 0.56 gm of aluminium oxide.
Explain law of conservation of mass.
50 g of 10% lead nitrate is mixed with 50 g of 10% sodium chloride in a closed vessel. After the reaction has taken place, it was found that 6.83 g of lead chloride was precipitated. Besides, the reaction mixture contained 90 g water and sodium nitrate. Calculate the amount of sodium nitrate formed.
Name and explain two important laws of chemical combination ?
What are the postulates of Dalton’s atomic theory of matter?
Hydrogen and oxygen combine in two different ways to produce water and hydrogen peroxide. Which of Dalton’s law does this observation confirm? Explain.
State drawbacks of Dalton’s atomic theory of matter.
Give an illustration based on atomic theory for the difference between an element, compound and mixture.
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