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Atoms And Molecules

Question
CBSEENSC9005072
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Which has more number of atoms, 100 grams of sodium or 100 grams of iron (given atomic mass of Na = 23 u, Fe = 56 u)?

Solution
23 space g r a m space a t o m i c space u n i t space o r space 23 space g r a m space s o d i u m space left parenthesis 1 space m o l e right parenthesis space space space equals space 6.022 space cross times space 10 to the power of 23 space a t o m s therefore space space space 100 space g r a m space a t o m i c space u n i t space o r space space 23 space g r a m space s o d i u m space left parenthesis 1 space m o l e right parenthesis space space space space equals space fraction numerator 6.022 space cross times space 10 to the power of 23 space cross times space 100 over denominator 23 end fraction equals space 2.617 space cross times space 10 to the power of 24 space space a t o m s
Again space 56 space gram space atomic space unit space or space 56 space grams space iron space left parenthesis 1 space mole right parenthesis space space space equals space 6.022 space cross times space 10 to the power of 23 space atoms space space space therefore space space space 100 space gram space atomic space unit space or space 56 space grams space iron space left parenthesis 1 space mole right parenthesis space equals space 1.075 space cross times space 10 to the power of 23 space atoms Thus space 100 space straight g space of space space carbon space has space more space atoms space than space 100 space straight g space of space iron space atoms.

Some More Questions From Atoms And Molecules Chapter

What are polyatomic ions? Give examples.

Write the chemical formulae of the following:

(a) Magnesium chloride
(b) Calcium oxide
(c) Copper nitrate 
(d) Aluminium chloride
(e) Calcium carbonate

Give the names of the elements in the following compounds.

(a) Quick lime
(b) Hydrogen bromide
(c) Baking powder 
(d) Potassium sulphate.

Calculate the molar mass of the following substances:

(a) Ethylene
(b) Sulphur molecule, S8
(c) Phosphorus molecule, P4
(d) Hydrochloric acid, HCl
(e) Nitric acid, HNO3.

What is the mass of:

(a) 1 mole of nitrogen atoms

(b) 4 moles of aluminium atoms

(c) 10 moles of sodium sulphite.

Convert into mole

(a) 12 gm of oxygen gas

(b) 20 gm of water

(c) 22 gm of carbon dioxide.

What is the mass of?

(a) 0.2 mole oxygen atoms.

(b) 0.5 mole of water molecules.

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.

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