Chemistry Conservation of Mass Quiz
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Questions and Answers

What does the law of conservation of mass state about chemical reactions?

  • The mass of reactants must equal the mass of products. (correct)
  • Mass can be created in a chemical reaction.
  • Mass is irrelevant to chemical reactions.
  • Mass can be destroyed in a chemical reaction.

Which of the following is true when balancing chemical equations?

  • Coefficients can be used to adjust the number of atoms. (correct)
  • Balancing is only necessary for gases.
  • You can change the subscripts to balance the equation.
  • Elements with the same mass remain unbalanced.

What is the first step recommended when balancing chemical equations?

  • Balance hydrogen atoms.
  • Begin with an open system.
  • Balance oxygen atoms.
  • Balance elements that are not hydrogen or oxygen. (correct)

In a closed system during a chemical reaction, what happens to gases?

<p>Gases remain trapped and affect mass. (C)</p> Signup and view all the answers

How do coefficients in chemical equations function?

<p>They indicate the amount and ratios of reactants to products. (C)</p> Signup and view all the answers

Which of the following describes a polyatomic ion when balancing chemical equations?

<p>Count it as a whole group if present on both sides. (D)</p> Signup and view all the answers

What must be done if coefficients in a chemical equation can be simplified?

<p>Adjust them to the simplest form. (B)</p> Signup and view all the answers

What is essential to check after balancing a chemical equation?

<p>That all elements have equal amounts on both sides. (A)</p> Signup and view all the answers

What is true about the conservation of mass in a chemical reaction?

<p>The total mass of reactants is equal to the total mass of products. (D)</p> Signup and view all the answers

In an open system, gases can escape during a chemical reaction.

<p>True (A)</p> Signup and view all the answers

What must be balanced first when balancing a chemical equation?

<p>Elements that are not hydrogen or oxygen.</p> Signup and view all the answers

The mass of the _____ must equal the mass of the products in a chemical reaction.

<p>reactants</p> Signup and view all the answers

Match the following steps to their purposes in balancing chemical equations:

<p>Balance hydrogen = Last step in balancing Balance oxygen = Second last step in balancing Count polyatomic ions = Considered as a whole group Check all atoms = Final review to ensure balance</p> Signup and view all the answers

What is the role of coefficients in a chemical equation?

<p>To indicate the amounts of reactants and products (A)</p> Signup and view all the answers

Changing subscript numbers in a chemical formula is acceptable to balance an equation.

<p>False (B)</p> Signup and view all the answers

What is the result of a chemical reaction in a closed system?

<p>Mass remains the same. (C)</p> Signup and view all the answers

Only the product side of a chemical equation must be balanced according to the law of conservation of mass.

<p>False (B)</p> Signup and view all the answers

What must be true about the number of atoms in the reactants and products in a balanced chemical equation?

<p>They must be equal.</p> Signup and view all the answers

The conservation of mass implies that the total mass of the _____ must equal the total mass of the products.

<p>reactants</p> Signup and view all the answers

Match the following elements to the order in which they are balanced in a chemical equation:

<p>Oxygen = 3 Hydrogen = 5 Individual Element = 6 Non-Hydrogen/Oxygen Elements = 1</p> Signup and view all the answers

Which of the following is a rule for balancing chemical equations?

<p>Use coefficients to adjust the number of atoms. (A)</p> Signup and view all the answers

Polyatomic ions should be counted as individual atoms when balancing equations.

<p>False (B)</p> Signup and view all the answers

What should be done to coefficients if they can be simplified after balancing a chemical equation?

<p>They should be reduced.</p> Signup and view all the answers

Flashcards

Law of Conservation of Mass

The law of conservation of mass states that the total mass of the reactants in a chemical reaction must equal the total mass of the products. This means that matter cannot be created or destroyed, only transformed.

Open vs. Closed Systems

A chemical reaction in a closed system follows the law of conservation of mass. An open system allows for matter to escape, which can affect the mass of the products.

Understanding Coefficients

Coefficients in a chemical equation represent the number of molecules of each reactant and product involved in the reaction. They're like scaling factors to balance the number of atoms on both sides of the equation.

Balancing Chemical Equations

Balancing chemical equations ensures that the number of atoms of each element on the reactant side equals the number of atoms of that element on the product side. It's like ensuring all the ingredients are accounted for in a recipe.

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Balancing Rules

To balance an equation, you can only change the coefficients in front of each chemical formula. You can't change the subscripts, as they represent the actual molecule.

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Balancing Order

When balancing chemical equations, start by balancing elements that are not hydrogen or oxygen. These are usually balanced first as the other two elements are more commonly found in multiple reactants and products.

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Balancing Polyatomic Ions

Treat polyatomic ions as a single unit when balancing equations. You would balance the whole group, not each atom individually.

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Balancing Oxygen and Hydrogen

After balancing all other elements, balance oxygen and hydrogen last. They are typically involved in several reactants and products, making them easier to balance at the end.

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Study Notes

Law of Conservation of Mass

  • Mass cannot be created or destroyed in a chemical reaction.
  • The total mass of the reactants equals the total mass of the products (in a closed system).
  • Example: 5g of hydrogen + 2.5g of oxygen = 7.5g of water.
  • Open system: Reaction occurs in a non-sealed container, allowing gases to escape.

Application to Chemical Equations

  • The quantity of matter (number of each atom) in reactants equals the quantity in products.
  • This results in equal mass on both sides. (Atoms are just rearranged, not created or destroyed, following the law).

Coefficients in Chemical Equations

  • Coefficients are numbers placed before chemical formulas to indicate the number of molecules.
  • They represent the ratio of reactants needed to make products.
  • Coefficients balance the number of atoms on both sides of the equation.

Balancing Chemical Equations

  • Balancing ensures equal atoms on both sides, upholding the Law of Conservation of Mass.
  • Do not change subscripts (these define the specific compound).
  • Use coefficients to adjust the number of atoms.

Balancing Equation Order

  • Prioritize balancing elements other than hydrogen and oxygen.
  • Treat polyatomic ions as a single unit if they appear on both sides.
  • Balance oxygen atoms.
  • Balance hydrogen atoms.
  • Balance any remaining single elements.
  • Verify the equality of atoms on both sides.
  • Simplify coefficients (reduce if necessary).

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Description

Test your understanding of the Law of Conservation of Mass in chemistry. This quiz covers key concepts such as mass in chemical reactions, balancing equations, and the role of coefficients. Prepare to apply these principles in various scenarios.

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