Counting Atoms and Balancing Chemical Equations

What does the Law of Conservation of Mass state?

• The number of atoms never changes during a chemical reaction

• The number of atoms always changes during a chemical reaction

• The number of atoms sometimes changes during a chemical reaction

• The number of molecules never changes during a chemical reaction

Tags

NGSS.MS-PS1-5

What is the left part of a chemical equation called?
2H_{2 +} O₂ --> 2H₂O

• Reactants
• Products 
• Yields 
• Chemical Equation 

What is the right part of a chemical equation called...
2H_{2 +} O₂ --> 2H₂O

• Reactants
• Products 
• Yields 
• Chemical Equation 

What is the total number of atoms present in 5Na₃PO₄

• 5
• 40
• 55
• 8

Tags

NGSS.MS-PS1-1

How many Mn atoms are found in the following compound?
3Cr(MnO₄)₆

• 3
• 4
• 6
• 18

Tags

NGSS.MS-PS1-1

What is the little number after an element in a chemical equation called.
Example: H₂

• Coefficient 
• Subscript
• Atom
• Equation

Tags

NGSS.MS-PS1-1

What is the number before a chemical formula called?
Ex: 2H₂ + O₂ --> 2H₂O

• Coefficient
• Subscript
• Atom
• Equation

How many aluminum atoms are in Al₂(SO₄)₃?

• 1
• 2
• 3
• 4

Tags

NGSS.MS-PS1-1

We learned to determine if a chemical equation is balanced

• By counting the number of atoms before and after the reaction.

• By calculating the molar mass of all the substances involved.

• By calculating the moles of all the substances involved.

• By dividing the number of atoms by the number of moles for each substance involved

Tags

NGSS.MS-PS1-5

Is the following equation balanced?
2C₂H₂ + 5O₂ --> 4CO₂ + 2H₂O

• yes
• no

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5