Chapter 7 Section 3.2: Molar Mass & Percentage Composition

Chapter 7 Section 3.2: Molar mass & Percentage Composition

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What is the formula mass of (NH₄)₂CO_3?

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What is the molar mass of (NH₄)₂CO_3?

​Recall

​Practice problem H on page 240 what is the mass in grams of 2.50 mol of oxygen gas (O₂)

​Practice problem H on page 240 what is the mass in grams of 2.50 mol of oxygen gas (O₂)

​Practice problem H on page 240 what is the mass in grams of 2.50 mol of oxygen gas (O₂)

​Practice problem H on page 240 what is the mass in grams of 2.50 mol of oxygen gas (O₂)

​Sample Problem I on Board

​Why find percentage composition?

​Sample problem J: Find the percentage composition of copper(I) sulfide Cu₂S

• ​First step: find the total molar mass of the compound Cu₂S

  • ​2 Cu= 2 x 63.55

  • ​1 S= 1 x 32.07

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What is the formula mass for Cu₂S (Round to 1 decimal place)

​​Sample problem J: Find the percentage composition of copper(I) sulfide Cu₂S

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Find the percentage composition of lead in PbCl_2.

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Find the percentage composition of Chlorine in PbCl_2.