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Question 1:

What is the purpose of balancing a chemical equation?

A) To ensure that the reaction obeys the law of conservation of mass
B) To indicate the physical state of each reactant and product
C) To determine the energy change of the reaction
D) To identify the catalysts involved in the reaction

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Explanation: The correct answer is A) To ensure that the reaction obeys the law of conservation of mass. Balancing a chemical equation is important to maintain the law of conservation of mass, which states that matter cannot be created or destroyed in a chemical reaction. By balancing the equation, the number of atoms of each element on both sides of the equation is equal.

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Question 2:

What is the coefficient of oxygen (O2) when the following equation is balanced: CH4 + O2 → CO2 + H2O?

A) 1
B) 2
C) 3
D) 4

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Explanation: The correct answer is B) 2. To balance the equation, the coefficient of oxygen (O2) must be 2. This ensures that there are equal numbers of oxygen atoms on both sides of the equation. The balanced equation becomes: CH4 + 2O2 → CO2 + 2H2O.

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Question 3:

Which of the following guidelines should be followed when balancing a chemical equation?

A) Only adjust the coefficients of the reactants
B) Change the subscripts of the reactants and products
C) Balance the elements in the order they appear in the equation
D) Start by balancing the elements that appear in the smallest number

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Explanation: The correct answer is C) Balance the elements in the order they appear in the equation. When balancing a chemical equation, it is important to balance the elements in the order they appear in the equation. Start with elements that appear only once on each side and then proceed to elements that appear multiple times.

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Question 4:

What is the coefficient of water (H2O) when the following equation is balanced: C2H6 + O2 → CO2 + H2O?

A) 1
B) 2
C) 3
D) 4

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Explanation: The correct answer is D) 4. To balance the equation, the coefficient of water (H2O) must be 4. This ensures that there are equal numbers of hydrogen and oxygenatoms on both sides of the equation. The balanced equation becomes: C2H6 + 7O2 → 2CO2 + 6H2O.

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Question 5:

What is the coefficient of carbon dioxide (CO2) when the following equation is balanced: C3H8 + O2 → CO2 + H2O?

A) 1
B) 2
C) 3
D) 4

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Explanation: The correct answer is A) 1. To balance the equation, the coefficient of carbon dioxide (CO2) is already 1. The equation is already balanced in terms of carbon dioxide.