Question

calculate the number of moles in a) 1.11 gram of calcium chloride
b) 1.5 into 10^30 molecules of ammonia

Answer 1

Answer:

a.3 mole.

b.the figures

Explanation:

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Answer 2

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Given:

• 1.11 grams of calcium chloride
• 1.5 × 10^ 30 molecules of ammonia

To find:

Moles = ?

Solution:

1) Calcium chloride = CaCl2

Mass of calcium (Ca) = 40 gm

Mass of chlorine (Cl) = 35.5 gm

Molecular mass of CaCl2 = 40 + 35.5 + 35.5 = 111g

Mass = 1.11 gm

$\\ \\ Moles = \dfrac{ Mass }{ \: Molar \: mass} \\ \\ = \dfrac{1.11}{111} \\ \\ = \dfrac{111 \times 10 {}^{ - 2} }{ 111}$

$\\ \\ = 1 \times 10 {}^{ - 2} \: moles \: or \: 0.01 \: moles$

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2) Ammonia = NH3

Avogadros number = 6.02 × 10^23

Number of molecules = 1.5 × 10^30 molecules

$\\ \\ Moles = \dfrac{ \:Number \: of \: molecules }{6.02 \times 10 {}^{23} } \\ \\ = \dfrac{1.5 \times {10}^{30} }{6.02 \times 10 {}^{23} } \\ \\ = 0.25 \: \times 10 {}^{7} moles$

Answer:

• Moles of 1.11 gm calcium chloride is 1 × 10 ^-2 or 0.01 moles
• Moles of 1.5 × 10^30 molecules ammonia is 0.25 × 10^ 7 moles

Formulas:

$\\ \\ Moles \: = \dfrac{mass}{molar \: mass} \\ \\ Moles = \dfrac{molecules}{6.02 \times 10 {}^{23} } \\ \\ Moles = \dfrac{volume}{22.4}$

Basic points:

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