Q4 of 16 Page 57

Write answers to the following questions and explain your answers.

Explain with examples what is meant by a 'mole' of a substance.

1 mole of a compound is the mass of that substance in grams equal in magnitude to its molecular mass. The SI unit is mol.

Number of moles of a substance (n) =


(Mass of substance in grams)/(Molecular mass of substance)


the molecular mass of oxygen is 32u, and therefore 32g oxygen is 1mole of oxygen. The molecular mass of water is 18u. Therefore, 18g of water make 1 mole of water.


More from this chapter

All 16 →
4

Write answers to the following questions and explain your answers.

Explain the need for a reference atom for atomic mass. Give some information about two reference atoms.

 4

Write answers to the following questions and explain your answers.

What is meant by Unified Atomic Mass.'

 5

Write the names of the following compounds and deduce their molecular masses.

Na2SO4, K2CO3, CO2, NaOH, MgCl2, AlPO4, NaHCO3

 6

Two samples ‘m’ and ‘n’ of slaked lime were obtained from two different reactions. The details about their composition are as follows:

‘sample m’ mass: 7g


Mass of constituent oxygen: 2g


Mass of constituent calcium: 5g


‘sample n’ mass: 1.4g


Mass of constituent oxygen: 0.4g


Mass of constituent calcium: 1.0g


Which law of chemical combination does this prove? Explain.