STEM and STEM HONORS Midterm Exam Quiz

Is the following equation balanced or unbalanced?
Fe + S --> FeS

• balanced
• unbalanced

True or False: When balancing chemical equations the subscripts can change.

• true
• false

Which of the Following Correctly Balances this Equation? 
_H₂+_Cl₂ --> _HCl

• 2H₂ + Cl₂ --> 4HCl
• H₂+Cl₂ --> 2HCl
• 3H₂ + 3Cl₂ --> HCl
• H + Cl --> HCl

When balancing equations a ____ can be placed to the left of a formula of a substance to make the equations balanced

• charge
• subscript
• random number
• coefficient

When balancing equations what does
 -->
mean?

• subscript
• equals
• it is just an arrow
• yield

Classify the following chemical reaction:
4P +5O₂ --> P₄O₁₀

• single replacement
• double replacement
• synthesis
• decomposition

Which of the following is an unbalanced equation?

• CaCO₃ --> CaO + CO₂
• PbO₂ + 2H₂-->2Pb + H₂O
• 2Na+ 2H₂O-->2NaOH + H₂
• CS₂ + 2O₂ --> CO₂ + 2SO

Which of the following is an example of synthesis?

• Na + Br₂ --> NaBr
• KClO₃ --> KCl + O₂
• HgO + Cl₂-->HgCl + O₂
• Cl₂ + NaBr --> NaCl + Br₂

Which of the following is evidence of a chemical reaction?

• fizzing
• water changing to ice
• saltwater
• paper being cut in half

When a chemical reaction is classified as decomposition what happens in the experiment?

• The elements are combined to create one chemical formula.
• The elements break down
• The elements replace each other