Question

.a. Calculate the molecular mass of Ca(OH)2 (atomic mass: Ca 40u: O:16u H:1u)


b. Write the formula for Aluminium Chloride and calculate its molecular mass( atomic msss: Al 27u: Cl: 35.5u) 1.5+1.5

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Answer 1

Answer -

a) Molecular mass is the sum total of mass of each atoms present in it.

➩ Molecular mass of $\rm Ca(OH)_2 = Mass\: of \:Ca + 2 ( Mass\: of \:O + Mass\: of \:H )$

$\rm = 40 + 2 ( 16 + 1 )$

$\rm = 40 + 2 ( 17 )$

$\rm = 40 + 34$

$\rm = 74 u$

➩ Molecular mass of $\rm Ca(OH)_2 = 74u$

b) Aluminium chloride

➩ Valency of Al - 3

➩ Valency of Cl - 1

By cross multiplication

➩ Aluminium chloride = $\rm AlCl_3$

Calculating molecular mass -

$\rm AlCl_3 = 27 + 3 ( 35.5 )$

$\rm = 27 + 106.5$

$\rm = 133.5 u$

Molecular mass of $\rm AlCl_3 = 133.5u$

Answer 2

Answer:

a) Molecular mass is the sum total of mass of each atoms present in it.

➩ Molecular mass of \rm Ca(OH)_2 = Mass\: of \:Ca + 2 ( Mass\: of \:O + Mass\: of \:H )Ca(OH)

2

=MassofCa+2(MassofO+MassofH)

\rm = 40 + 2 ( 16 + 1 )=40+2(16+1)

\rm = 40 + 2 ( 17 )=40+2(17)

\rm = 40 + 34=40+34

\rm = 74 u=74u

➩ Molecular mass of \rm Ca(OH)_2 = 74uCa(OH)

2

=74u

b) Aluminium chloride

➩ Valency of Al - 3

➩ Valency of Cl - 1

By cross multiplication

➩ Aluminium chloride = \rm AlCl_3AlCl

3

Calculating molecular mass -

\rm AlCl_3 = 27 + 3 ( 35.5 )AlCl

3

=27+3(35.5)

\rm = 27 + 106.5=27+106.5

\rm = 133.5 u=133.5u

Molecular mass of \rm AlCl_3 = 133.5uAlCl

3

=133.5u

Explanation:

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