Question

Calculate the mass in grams of each elemental sample:

1. 1.16×10²⁰ uranium atoms

2.  3.88×10²² zinc atoms

3.  4.04×10²³ lead atoms

4.  6.55×10²⁴ silicon atoms

Answer 1

1.) ANSWER:

Number of uranium atom = 1.16 x 10²⁰ uranium atom

Atomic mass of uranium atom = 238.029 g/mol

6.022 x 10²² atoms of uranium = 1 mole of uranium

1 atom of uranium = 1/(6.022 x 10²³) mole of uranium = 1.67 x 10^-24 moles of uranium

1.16 x 10²⁰ atoms uranium atom = 1.16 x 10²⁰ x 1.67 x 10^-24 moles of uranium

= 1.94 x 10^-4 moles of uranium.

Now,

mass of uranium atom = molecular mass x number of moles

= 238.029 g/mol x 1.94 x 10^-4 mol

= 0.0462 g

Hence, mass of uraniun atom is 0.0462 grams.

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2.) ANSWER:

Number of zinc atom = 3.88 x 10²² zinc atom

Atomic mass of zinc atom = 65.409 g/mol

6.022 x 10²² atoms of zinc = 1 mole of zinc

1 atom of zinc = 1/(6.022 x 10²³) mole of zinc = 1.67 x 10^-24 moles of zinc

3.88 x 10²² atoms zinc atom = 3.88 x 10²² x 1.67 x 10^-24 moles of zinc

= 6.48 x 10^-2 moles of zinc.

Now,

mass of zinc atom = molecular mass x number of moles

= 65.409 g/mol x 6.48 x 10^-2 mol

= 4.24 g

Hence, mass of zinc atom is 4.24 grams.

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3.) ANSWER:

Number of lead atom = 4.04 x 10²³ lead atom

Atomic mass of lead atom = 207.2 g/mol

6.022 x 10²² atoms of lead = 1 mole of lead

1 atom of lead = 1/(6.022 x 10²³) mole of lead = 1.67 x 10^-24 moles of lead

4.04 x 10²³ atoms lead atom = 4.04 x 10²³ x 1.67 x 10^-24 moles of lead

= 6.75 x 10^-1 moles of lead.

Now,

mass of lead atom = molecular mass x number of moles

= 207.2 g/mol x 6.75 x 10^-1 mol

= 139.86 g

Hence, mass of lead atom is 139.86 grams.

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4.) ANSWER:

Number of silicon atom = 6.55 x 10²⁴ silicon atom

Atomic mass of silicon atom = 30.974 g/mol

6.022 x 10²² atoms of silicon = 1 mole of silicon

1 atom ofsilicon = 1/(6.022 x 10²³) mole of silicon = 1.67 x 10^-24 moles of silicon

6.55 x 10²⁴ atoms silicon atom = 6.55 x 10²⁴ x 1.67 x 10^-24 moles of silicon

= 10.94 moles of silicon.

Now,

mass of silicon atom = molecular mass x number of moles

= 30.974 g/mol x 10.94 mol

= 43.48 g

Hence, mass of silicon atom is 43.48 grams.

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