BL Ch 3 Chem Reactions and Stoich

Multiple Choice

Which scientist is credited with formulating the Law of Conservation of Mass, which is the basis for stoichiometry?

• Antoine Lavoisier

• Isaac Newton

• Dmitri Mendeleev

• Marie Curie

Open Ended

Why is the Law of Conservation of Mass fundamental to the study of stoichiometry in chemistry?

Multiple Choice

What is the main purpose of a chemical equation?

• To represent chemical reactions concisely

• To describe physical changes

• To list all elements in a compound

• To show the color of chemicals

Multiple Choice

What does the (g) symbol indicate in a chemical equation?

• Gas state

• Solid state

• Liquid state

• Aqueous solution

Multiple Select

Which of the following statements about balancing chemical equations are correct?

• Coefficients are used to balance the equation.

• Changing subscripts changes the identity of the compound.

• Reactants are always on the right side of the equation.

• The law of conservation of mass must be followed.

Open Ended

Explain why coefficients are used in chemical equations instead of changing subscripts.

Multiple Choice

Which of the following is NOT one of the three main types of chemical reactions introduced in the lesson?

• Combination reactions

• Decomposition reactions

• Combustion reactions

• Displacement reactions

Open Ended

Compare and contrast combination reactions and decomposition reactions. How do the reactants and products differ in each type?

Multiple Select

Select all the correct statements about combustion reactions.

• They are generally rapid reactions that produce a flame.

• They usually involve oxygen as a reactant.

• They always produce carbon dioxide and water.

• They can occur without oxygen.

Multiple Choice

Which of the following chemical equations represents a combination reaction?

• 2 Mg(s) + O2(g) → 2 MgO(s)

• CaCO3(s) → CaO(s) + CO2(g)

• CH4(g) + 2 O2(g) → CO2(g) + 2 H2O(g)

• 2 KClO3(s) → 2 KCl(s) + O2(g)

Open Ended

Explain the difference between formula weight and molecular weight, providing an example of each.

Multiple Choice

Why do ionic compounds use empirical formulas instead of molecular formulas?

• Because ionic compounds exist as a three-dimensional order of ions and not as discrete molecules.

• Because ionic compounds are always gases at room temperature.

• Because ionic compounds are made only of metals.

• Because ionic compounds have variable compositions.

Multiple Choice

What does the equation % Element = [(number of atoms)(atomic weight) / FW of the compound] × 100 calculate?

• The percent composition of an element in a compound.

• The molar mass of a compound.

• The number of moles in a sample.

• The empirical formula of a compound.

Open Ended

Explain the significance of Avogadro's number in laboratory measurements and why it is important for chemists.

Multiple Select

Which of the following statements about molar mass are correct?

• The molar mass of a substance is the mass of 1 mole of that substance.

• For diatomic elements, the molar mass is twice the atomic weight.

• The formula weight in amu is numerically equal to the molar mass in g/mol.

• Molar mass is only used for ionic compounds.

Open Ended

Describe how moles act as a bridge between the molecular scale and the real-world scale in chemistry. Give an example to support your explanation.

Open Ended

What is one question you still have about chemical reactions or stoichiometry after this lesson?

Multiple Choice

Which of the following statements best describes the relationship between moles and Avogadro's number for molecules and formula units?

• One mole of molecules contains Avogadro's number of molecules, and one mole of formula units contains Avogadro's number times the number of atoms or ions in the compound.

• One mole of molecules contains twice Avogadro's number of molecules.

• One mole of formula units contains half Avogadro's number of atoms.

• One mole of atoms contains Avogadro's number times the number of molecules.

Open Ended

How does the Law of Conservation of Mass, as described by Antoine Lavoisier, form the basis of stoichiometry in chemistry?

Open Ended

List and briefly describe the steps required to determine the empirical formula from percent composition.

Open Ended

The compound para-aminobenzoic acid (PABA) is composed of carbon (61.31%), hydrogen (5.14%), nitrogen (10.21%), and oxygen (23.33%). Find the empirical formula of PABA.