Chemistry Class 11 NCERT Solutions: Chapter 1 Some Basic Concepts of Chemistry Part 4

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Q: 10. In three moles of ethane calculate following:

(i) Number of moles of carbon atoms

(ii) Number of moles of hydrogen atoms

(iii) Number of molecules of ethane

Answer:

(i) 1 mole of contains moles of carbon atoms.

∴ Number of moles of carbon atoms in moles of

(ii) 1 mole of contains 6 moles of hydrogen atoms.

∴ Number of moles of carbon atoms in moles of

(iii) 1 mole of contains molecules of ethane.

∴ Number of molecules in 3 moles of

Q: 11. What is the concentration of sugar

In are dissolved in enough water to make a final volume up to ?

Answer:

Molarity (M) of a solution is given by,

∴ Molar concentration of sugar

Q: 12. If the density of methanol is what is its volume needed for making of its 0.25 M solution?

Answer:

Molar mass of methanol

Molarity of methanol solution

(Since density is mass per unit volume)

Applying,

(Given solution) (Solution to be prepared)