Chapter 3 Section 5

An empirical formula:

• is a formula that calculates the coefficients of a compound in a balanced equation.
• is the simplest whole-number ratio of moles of elements in the compound.

Which one is empirical?

• H₂O₂
• C₂H₆O₁₂
• CaCl₂
• N₂O₈

Which pair has the same empirical formula?

• NaCrO₄ and Na₂Cr₂O₇
• C₂H₄O₂ and C₆H₁₂O₆
• C₃H₆O₃ and C₂H₆O₂
• CH₄ and C₂H₆

Name the following ionic compound: MgSO₄*7H₂O

• magnesium sulfate * hexahydarte
• magnesium sulfate hexahydarte
• magnesium sulfate heptahydrate
• magnesium sulfate* heptahydrate

Name the following hydrate:  NaCl * 5H₂O

• sodium chloride 
• sodium monochloride pentahydrate
• sodium chloride pentahydrate
• pentahydrate

What is the best method for removing water from a hydrated compound?

• freezing

• filtration

• distillation

• heating

A hydrate of magnesium chloride is present and the following data is collected:

mass of evaporating dish = 22.130 grams

mass of dish + hydrate = 25.290 grams

mass of dish and contents after heating = 23.491 grams

What is the mass of the anhydrous MgCl₂?

• 1.799 g

• 3.160 g

• 1.361 g

• 23.491 g

Tags

NGSS.HS-PS1-7

If 15.6 g of hydrate are heated and only 11.7 g of anhydrous salt remain, calculate the % of water lost.

• 25.9%
• 19.2%
• 37.9%
• 76.3%

Crucible, cover: 19.8 g
Crucible, cover, and hydrate: 23.0g
Crucible, cover, and salt: 21.5g
Calculate % of water lost.

• 90.0%
• 46.9%
• 39.3%
• 45.5%

T/F
A compounds molecular formula can be the same as its empirical formula

• True
• False