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Balancing Chemical Equations 4 questions

Balancing Chemical Equations

New Regents original practice • Name: ____________________ Date: __________ Show your work for written answers.

Use the smallest whole-number coefficients when balancing. A coefficient of 1 can be omitted. Keep the subscripts in each chemical formula unchanged.

Question 1

How many oxygen atoms are represented by 3Ca(NO₃)₂?

  1. 6
  2. 8
  3. 9
  4. 18

Question 2

Balance H₂ + O₂ → H₂O. Show how many H and O atoms appear on each side of your balanced equation.

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Question 3

A student balances oxygen by replacing H₂O with H₂O₂. Explain why this change is invalid.

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Question 4

Which equation is balanced?

  1. Al + O₂ → Al₂O₃
  2. 4Al + 3O₂ → 2Al₂O₃
  3. 2Al + O₂ → Al₂O₃
  4. 4Al + 2O₂ → 2Al₂O₃

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Carbon and Hydrogen in a Burner 4 questions

Carbon and Hydrogen in a Burner

Use the information below to answer questions 5–8.

A laboratory burner uses propane, C3H8. When it undergoes complete combustion in oxygen, the products are carbon dioxide and water. The starting equation is C3H8 + O2 → CO2 + H2O.

Question 5

With one molecule of propane reacting, how many molecules of CO₂ are needed to account for all the carbon atoms?

  1. 1
  2. 2
  3. 3
  4. 4

Question 6

Write the balanced equation for complete propane combustion using the smallest whole-number coefficients.

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Question 7

A proposed equation is C₃H₈ + 4O₂ → 3CO₂ + 4H₂O. Identify the unbalanced element and give its atom count on each side.

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Question 8

Explain what the coefficient 4 in front of H₂O means in the balanced propane equation at the particle level.

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