Unit 9 Formula Stoich Test Review

Name the following hydrate:  NaCl * 5H₂O

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

Tags

NGSS.MS-PS1-1

A compound is a hydrate when it...

• is composed of only hydrogen and oxygen
• is a state of water
• contains water in the compound

• repels water from the compound

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.
• is the actual formula of a molecular compound.

• a relationship between an empirical formula and its molecular formula.

Which of the following is an empirical formula? 

• CH₂O

• C₂H₄O₂

• C₄H₈O₄

• C₆H₁₂O₆

How do you calculate the percent by mass of an element in a compound? 

• Add up the mass of protons and neutrons, then divide by two.

• Divide the mass of the element by the total mass of the compound and multiply by 100.

• Add up the atomic masses of the elements, then divide by the number of the elements.

• Find the relative mass of any atom by adding the number of protons to the number of neutrons, then dividing by that total number.

Tags

NGSS.HS-PS1-7

A 15.67 g sample of a hydrate of magnesium carbonate was heated to drive off the water. The mass was reduced to 7.58 g. What is the formula of the hydrate?

• MgCO₃ · 5H₂O
• MgCO₃ · 4H₂O
• MgCO₃ · 6H₂O
• MgCO₃ · 1H₂O

Tags

NGSS.HS-PS1-2

NGSS.HS-PS1-7

A 4.175 gram sample of a certain hydrate of copper (II) sulfate, CuSO4•xH2O, is heated until all the water is driven off. The resulting anhydrous compound weighs 3.120 grams. What is the formula of the hydrate?

• CuSO4•H2O

• CuSO4•3H2O

• CuSO4•6H2O

• CuSO4•4H2O

Tags

NGSS.HS-PS1-7

A 5.018 gram sample of a certain hydrate of magnesium sulfate, MgSO4•xH2O, is heated until all the water is driven off. The resulting anhydrous compound weighs 2.449 grams. What is the formula of the hydrate?

• MgSO4•9H2O

• MgSO4•8H2O

• MgSO4•7H2O

• MgSO4•6H2O

Tags

NGSS.HS-PS1-7

Find the percent composition of Cu₂S?

• Cu= 67.987%; S= 32.013%

• Cu= 79.854%: S= 20.145%

• Cu= 35.946%; S= 64.054%

• Cu= 39.925%; S= 20.151%

Tags

NGSS.HS-PS1-7

A sample with a molar mass of 34.00 g/mol is found to consist of 0.44 g H and 6.92 g O. Find its molecular formula.

• HO

• H₂O₂

• H₂O

• H_1/2O_1/2

Tags

NGSS.HS-PS1-1