Balancing Chemical Equations Review

What is a subscript in a chemical formula?

• A number written above and to the left of a chemical symbol that indicates the number of atoms of that element in a molecule.

• A number written below and to the right of a chemical symbol that indicates the number of atoms of that element in a molecule.

• A symbol that represents the type of bond between atoms in a molecule.

• A notation used to indicate the charge of an atom in a chemical formula.

How many atoms of aluminum are in the equation: 4Al + 3O₂ --> 2Al₂O₃?

• 2 atoms

• 4 atoms

• 6 atoms

• 8 atoms

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What does the principle of conservation of mass state?

• Matter can be created or destroyed in a chemical reaction.

• The total mass of the reactants is less than the total mass of the products.

• Matter is not created or destroyed in a chemical reaction; the total mass of the reactants equals the total mass of the products.

• The total mass of the products is always greater than the total mass of the reactants.

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NGSS.MS-PS1-5

What is a chemical equation?

• A symbolic representation of a chemical reaction, showing the reactants and products involved.

• A numerical representation of a chemical reaction.

• A graphical representation of a chemical reaction.

• A written description of a chemical reaction.

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How many phosphorus atoms are in PO₄?

• 1 phosphorus atom

• 2 phosphorus atoms

• 3 phosphorus atoms

• 4 phosphorus atoms

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What is the difference between an ionic bond and a covalent bond?

• An ionic bond is formed when electrons are shared between atoms, while a covalent bond is formed when electrons are transferred from one atom to another.

• An ionic bond is formed when electrons are transferred from one atom to another, while a covalent bond is formed when atoms share electrons.

• An ionic bond is a type of covalent bond that involves unequal sharing of electrons.

• An ionic bond is formed between two nonmetals, while a covalent bond is formed between a metal and a nonmetal.

What is the law of definite proportions?

• A chemical compound can have varying proportions of elements by mass.

• The law of definite proportions states that a chemical compound always contains the same proportion of elements by mass.

• The law of definite proportions applies only to gases and not to solids or liquids.

• The law of definite proportions is a principle that only applies to organic compounds.

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What is the role of coefficients in balancing equations?

• Coefficients are used to multiply the number of molecules of reactants and products to achieve balance in the equation.

• Coefficients indicate the temperature at which a reaction occurs.

• Coefficients represent the energy required for a reaction to take place.

• Coefficients are used to measure the pressure of the reactants.

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What is the significance of the arrow in a chemical equation?

• It indicates the temperature of the reaction.

• It shows the direction of the reaction, indicating that reactants are transformed into products.

• It represents the pressure conditions of the reaction.

• It denotes the phase of the reactants and products.

What is a coefficient in a chemical equation?

• A number that indicates the temperature of the reaction.

• A number placed in front of a chemical formula to indicate how many molecules or moles of that substance are involved in the reaction.

• A symbol that represents a chemical element.

• A type of chemical bond between atoms.

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NGSS.MS-PS1-5