Moles, Molar Mass, and Mass percent of compounds

Calculate the number of iron atoms in a 4.48 mole sample of iron

• 2.70 × 10²⁴ Fe atoms

• 5.70 × 10²⁴ Fe atoms

• 2.90 × 10⁴ Fe atoms

• 1.30 × 10³⁴ Fe atoms

A silicon chip used in an integrated circuit of a microcomputer has a mass of 5.68 mg. How many silicon (Si) atoms are present in the chip?

▫Convert mg to g : 5.68 mg X 10 ^-3

• 2.02 X 10 ^-4 atoms

• 1.22 X 10^-7 atoms

• 2.23 X 10²² atoms

• 1.22 X 10²⁰ atoms

A sample of element silver (Ag) has a mass of 21.46 g. how many moles of silver are in sample? How many atoms of silver are in sample?

• 2.198 X 10²⁰ atoms

• 0.1989 atoms

• 1.198 X 10²³ atoms

• 1.178 X 10²¹ atoms

What is the weight of 7.81 X 10 ²² atoms of Calcium?

• 5.19 g Co

• 4.19 g Co

• 12.14 g Co

• 7.10 g Co

Cobalt (Co) is a metal that is added to steel to improve its resistance to corrosion. Calculate the number of moles in a sample of cobalt containing 5.00 X 10²⁰ atoms

• 1.33 X 10 ^-12 mole

• 7.30 X 10 ^-2 mole

• 8.30 X 10 ^-4 mole

• 2.34 X 10 ^-3 mole

Calculate the molar mass of potassium dichromate K₂Cr₂O₇

• 354.30 g/mole

• 294.20 g/mole

• 221.30 g/mole

• 122.20 g/mole

What are the molecular weights of H₃PO₄

• 88.00 grams

• 91.00 grams

• 98.00 grams

• 92.00 grams

What are the molecular weights of Mn₂Se₇

• 662.60 grams

• 682.30 grams

• 622.30 grams

• 662.60 grams

What are the molecular weights of (NH₄)₂ SO₄

• 120.11 grams

• 132.17 grams

• 112.16 grams

• 113.19 grams

Mass percent of iron in iron(III) oxide, (Fe₂O₃)

• 89.68 %

• 44.36 %

• 78.69 %

• 69.94 %