Question

Determine the number of moles in each substance.
a. 3.25 x 1020 atoms of lead
b. 4.96 x 1024 molecules of glucose
c. 1.56 x 1023 formula units of sodium hydroxide
d. 1.25 x 1025 copper(ll) ions

Answer 1

Answer:

a) 5.4 * 10^-4 moles

b) 8.2 moles

c) 0.26 moles

d) 20.76 moles

Explanation:

a)Since 1 mole of a substance has 6.02 * 10^23 atoms

x moles is present in  3.25 x 1020 atoms of lead

3.25 x 1020 atoms of lead/6.02 * 10^23 atoms = 5.4 * 10^-4 moles

b) Since 1 mole of a substance has 6.02 * 10^23 molecules

x moles is present in  4.96 x 1024 molecules of glucose

x = 4.96 x 1024 molecules of glucose/6.02 * 10^23 molecules = 8.2 moles

c) Since 1 mole of a substance has 6.02 * 10^23 formula units

x moles is present in 1.56 x 1023 formula units of sodium hydroxide

x =  1.56 x 1023 formula units /6.02 * 10^23 = 0.26 moles

d) Since 1 mole of a substance has 6.02 * 10^23 ions

x moles is present in 1.25 x 1025 copper(ll) ions

x = 1.25 x 1025 copper(ll) ions/6.02 * 10^23 ions = 20.76 moles

Answer 2

The number of moles in lead is 5.40 × 10⁻⁴ moles

The number of moles in glucose is 8.24 moles

The number of moles in sodium hydroxide is 0.259 moles

The number of moles in copper (II) ions is 20.76 moles

The number of moles of a substance is equal to 6.022 × 10²³ atoms. The number of moles of each given substance can be calculated by relating it to the Avogadro's constant 6.022 × 10²³ atoms.

Starting with a from the given parameters, we have:

a)

• 1 mole of substance = 6.022 × 10²³ atoms
• x mole present in = 3.25 × 10²⁰ atoms of lead

Making x the subject of the formula, we have:

$\mathbf{x = \dfrac{1 \ mole \times 3.25 \times 10^{20} \ atoms }{6.022 \times 10^{23} \ atoms}}}$

x = 5.40 × 10⁻⁴ moles

b)

• 1 mole of substance = 6.022 × 10²³ molecules
• x moles present in = 4.96 ×10²⁴ molecules of glucose

$\mathbf{x = \dfrac{1 \ mole \times 4.96 \times 10^{24} \ molecules }{6.022 \times 10^{23} \ molecules}}}$

x = 8.24 moles

c)

• 1 mole of substance = 6.022 × 10²³ molecules
• x moles present in = 1.56 × 10²³ units of NaOH

$\mathbf{x = \dfrac{1 \ mole \times 1.56 \times 10^{23} \ units}{6.022 \times 10^{23} \ units}}}$

x = 0.259 moles

d)

• 1 mole of substance = 6.022 × 10²³ molecules
• x moles present in = 1.25 × 10²⁵ copper ions

$\mathbf{x = \dfrac{1 \ mole \times 1.25 \times 10^{25} \ ions }{6.022 \times 10^{23} \ ions}}}$

x = 20.76 moles

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