S2 Unit 7 Week 1 Homework (Due 01-12-2024)

What is the percent of oxygen by mass in a pure sample of FeC₂O₄?

• 39%

• 52%

• 44%

• 9.5%

Match the following compounds with their percent by mass of nitrogen.

• Ammonium sulfate

• 47%

• Ammonium nitrate

• 35%

• Urea (CH₄N₂O)

• 26%

• Ammonium chloride

• 21%

What is the percentage by mass of fluorine in sulfur hexafluoride, a potent greenhouse gas?

• 22.0%

• 59.2%

• 78.0%

• 87.7%

Tags

NGSS.HS-PS1-7

Find the mass percentage of water in ZnSO₄·7 H₂O.

• 43.86%

• 46.98%

• 10.04%

• 24.56%

• 56.54%

What is the mass percentage of water in the hydrate CuSO₄ · 5 H₂O?

• 36.08%

• 40.58%

• 24.56%

• 56.54%

A sample of a calcium chloride hydrate, CaCl₂ · x H₂O(s), has a mass of 4.72g. After heating to constant mass, the mass of the anhydrate is found to be 3.56g. What is the formula of the hydrate?

• CaCl₂ · 2H₂O

• CaCl₂ · H₂O

• CaCl₂ · 3H₂O

• CaCl₂ · 4H₂O

Answer explanation

The mass lost in this experiment is water. Convert the masses of water and anhydrous salt to moles and find the mole ratio to get the number of water molecules in the formula of the hydrate.

Be sure you have a correct chemical formula for the salt!

Tags

NGSS.HS-PS1-7

What is the name of Na₂CO₃ · 10 H₂O?

• sodium carbonate decahydrate

• sodium (II) carbonate decahydrate

• sodium carbon trioxide decahydrate

• sodium carbonate nonahydrate

Answer explanation

Name the salt as usual. Add the prefix corresponding to the number of water molecules to the word "hydrate" for the second part of the name.

The name of FeSO₄ · 7 H₂O is (a)  

• iron (II) sulfate heptahydrate
• iron sulfate heptahydrate
• iron (III) sulfate heptahydrate
• iron (II) sulfide hexahydrate

Answer explanation

Name the salt as usual. Add the prefix corresponding to the number of water molecules to the word "hydrate" for the second part of the name.

When a 100. g sample of a hydrate of X₂CO₃ (anhydrous molar mass = 153 g mol⁻¹) is heated until all the water is removed, it loses 54 percent of its mass. The formula of the hydrate is

• X₂CO₃·3 H₂O

• X₂CO₃·5 H₂O

• X₂CO₃·7 H₂O

• X₂CO₃·10 H₂O

Answer explanation

The mass lost in this experiment is water. Convert the masses of water and anhydrous salt to moles and find the mole ratio to get the number of water molecules in the formula of the hydrate.

Be sure you have a correct chemical formula for the salt!

Tags

NGSS.HS-PS1-7

A hydrate of Na₂CO₃ has a mass of 4.31 g before heating. After heating, the mass of the anhydrous compound is found to be 3.22 g. Determine the formula of the hydrate, and then identify the correct name of the hydrate.

• sodium carbonate dihydrate

• sodium carbonate bihydrate

• sodium bicarbonate

• sodium carbonate monohydrate

Answer explanation

The mass lost in this experiment is water. Convert the masses of water and anhydrous salt to moles and find the mole ratio to get the number of water molecules in the formula of the hydrate.

Be sure you have a correct chemical formula for the salt!

Tags

NGSS.HS-PS3-4