Balancing Chemical Equations

When dry ice (solid carbon dioxide) sublimes it goes directly from a solid to a gas. What type of change is occurring? 

• Chemical change
• Physical change
• None of the above 

How many oxygen atoms are present in the following? 
4Ca(OH)₂

• 4
• 6
• 8
• 1

Why must we balance chemical equations? 

• Our teacher said so
• to abide by the law of conservation of energy
• to abide by the law of conservation of mass

What is changed in a chemical reaction like this one? 
NaOH + HCl   →  NaCl + H₂O

• the number of atoms is changed
• molecules and compounds are changed 
• atoms are changed
• elements are changed 

 Fill in the blank to balance the chemical equation. 
2KI  +  ____Cl₂ →  2KCl  +  I₂

• 1
• 2
• 3
• 4

What coefficient should go in the blank space to balance the chemical equation? 
2Al  +____  HCl   →    2AlCl₃  +  3H2

• 2
• 4
• 3
• 6

How many atoms of carbon (C) are in C₆H₁₂O₆?

• 3
• 6
• 12
• 24

How many Hydrogen are in 4H₂O?

• 6
• 8
• 2
• 4

Which of the following reactions is balanced?

• 2CH₄ + O₂ -> CO₂ + H₂O
• CH₄ + 2O₂ -> CO₂ + H₂O
• CH₄ + 2O₂ -> CO₂ + 2H₂O
• None of the chemical equations are balanced.

How many HCl molecules do you need to balance this equation? 
Mg +  __HCl --->  MgCl₂ + H₂

• 1
• 2
• 3
• 4