Chemical Equations

What is a chemical equation?

• a.A way of calculating how many molecules are produced in a chemical reaction
• b.A shorthand representation of what happens in a chemical reaction
• c.A shorthand representation of the bonding in a molecule
• d.A method of comparing diatomic molecules.

What are the substances on the left side of a chemical equation called?

• a.Electrons
• b.Groups
• c.Products
• d.Reactants

What does the number in front of a molecular formula mean in a chemical equation?

• a.It shows that there is only one molecule present in a reaction
• b.It shows the number of reactions that took place
• c.It shows the number of that type of molecule involved in the reaction
• d.All of the choices

Can the subscripts in a chemical reaction be changed?

• a.Sometimes, depending on the energy released in the reaction
• b.Yes, to balance the equation
• c.Only for hydrogen, if there are water molecules on both sides of the reaction.
• d.o, the subscripts define the molecules in the reaction

Lavoisier observed that the mass of reactants is the same as the mass of the products after a reaction. Which of the following can you NOT conclude based on Lavosiers observation:

• a.The number of atoms in the reactants must be the same as the number of atoms in the products
• b.The number of molecules of reactant must be the same as the number of molecules of products
• c.No mass is lost or gained in the reaction
• d.The Law of Conservation of Mass

The law of definite proportions implies that:

• a.A chemical compound produced in a reaction will always have the same ratio of elements by mass, no matter what the source or amount of the reactants.
• b.Each particular chemical reaction produces substances with definite sizes and physical proportions
• c.The reactants in any chemical reaction will always create products in a one-to-one ratio
• d.In a chemical reaction, the ratio of product molecules will always equal the ratio of reactant molecules

What does it mean when a chemical equation is balanced?

• a.The equation represents equal weights of reactants and products
• b.The total of the coefficients (including those that equal 1) is the same on both sides of the equation
• c.There are the same number of molecules on either side of the equation
• d.There are equal numbers of each type of atom on both sides of the equation

What coefficient should be in front of the oxygen? 4 Al + __ O₂ → 2 Al₂O₃

• a.2
• b.3
• c.6
• d.No number (the equivalent of the number 1)

What are the correct coefficients to balance this equation? 12 HClO₄ + ___ P₄O₁₀ → ____ H₃PO₄ + _____Cl₂O₇

• a.1, 4, and 6
• b.2, 4, and 4
• c.1, 6, and 8
• d.2, 6, and 4

If you begin this reaction with 1 mole of Ba₃N₂ and 6 moles of HF, how many moles of each product do you get? Ba₃N₂ + 6 HF → ___ BaF₂ + ___ NH₃

• a.1 and 1
• b.6 and 6
• c.3 and 2
• d.3 and 6