Practice: Chemical Equations

How many HCl molecules do you need to balance this equation?

2Mg + ​ (a)   HCl ---> 2MgCl₂ + 2H₂

• 4
• 1
• 2
• 3

What coefficient should be used to make the following equation balanced?

N₂+O₂--> __?__NO

• 1

• 2

• 3

• 4

• 3
• 2

Balance this equation ​ (a)   N₂ + ​ (b)   H₂ --> ​ (c)   NH₃

• 1
• 3
• 2

Balance this equation. _CF₄ + _Br₂ → _CBr₄ + _F₂

• 3,1,2,1

• 1,2,1,2

• 2,2,2,2

According to the Law of Conservation of Mass (Matter), Matter cannot be ​ (a)   or ​ (b)   , it can only be ​ (c)   . This means however many atoms of an element we have before a reaction must be ​ (d)   to the number after a reaction.

• created
• destroyed
• changed
• equal

What is the total number of atoms present in 5Na₃PO₄

• 5
• 40
• 55
• 8

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

• Coefficient 

• Subscript

• Atom

• Equation

Which of the following equations are correctly balanced?

• 12CO₂ +H₂O --> C₆H₁₂O₆ + O₂

• CO₂ + 9H₂O --> C₆H₁₂O₆ + O₂

• CO₂ + H₂O --> 3C₆H₁₂O₆ + O₂

• 6CO₂ + 6H₂O --> C₆H₁₂O₆ + 6O₂

In 3P₂O₅, there are ​ (a)   phosphorus (P) atoms and ​ (b)   oxygen (O) atoms.

• 6
• 15
• 8
• 3
• 12
• 21