- Basic Math and Science Chemical Reactions and Stoichiometry Questions and Answers Flashcards

Which of the following describes an exothermic reaction?

Answer: Energy is released to the surroundings

Exothermic reactions release energy to the surroundings, making the products lower in energy than the reactants.

When balancing the equation __Fe + __O₂ → __Fe₂O₃, what are the correct coefficients?

Answer: 4, 3, 2

The balanced equation is 4Fe + 3O₂ → 2Fe₂O₃, conserving iron (4 atoms each side) and oxygen (6 atoms each side).

What is the molarity of a solution containing 2 moles of NaCl dissolved in 0.5 liters of solution?

Answer: 4 M

Molarity = moles of solute / liters of solution = 2 mol / 0.5 L = 4 M.

In a single replacement reaction, Zn + CuSO₄ → ZnSO₄ + Cu, what is the driving force?

Answer: Zinc is more reactive than copper and displaces it

Zinc is higher on the activity series than copper, so it displaces copper from the solution.

If 2 moles of H₂ react with 1 mole of O₂ to form water, and you start with 3 moles of H₂ and 1 mole of O₂, which is the limiting reagent?

Answer: O₂

O₂ is the limiting reagent because 1 mol O₂ can only react with 2 mol H₂, leaving 1 mol H₂ unused.

What is the law of conservation of mass as applied to chemical reactions?

Answer: The total mass of reactants equals the total mass of products

The law of conservation of mass states that matter is neither created nor destroyed in a chemical reaction, so mass is conserved.

How many grams of NaCl (molar mass 58.5 g/mol) are needed to make 2 moles of NaCl?

Answer: 117 g

Mass = moles × molar mass = 2 mol × 58.5 g/mol = 117 g.