Chemical Reactions and Stoichiometry Flashcards

In the reaction 2H₂ + O₂ → 2H₂O, how many moles of water are produced from 4 moles of H₂?

Answer: 4 moles

The molar ratio of H₂ to H₂O is 1:1, so 4 moles of H₂ produce 4 moles of H₂O.

Which type of reaction involves a single compound breaking down into two or more simpler substances?

Answer: Decomposition

Decomposition reactions break one compound into simpler products, such as 2H₂O → 2H₂ + O₂.

What is the molar mass of CO₂? (C=12, O=16)

Answer: 44 g/mol

CO₂ has one carbon (12) and two oxygens (2×16=32), giving 12+32=44 g/mol.

In a chemical equation, what does the law of conservation of mass require?

Answer: The number of atoms on both sides must be equal

Conservation of mass means atoms are neither created nor destroyed, so both sides must have the same number of each type of atom.

How many grams of NaCl (molar mass = 58.5 g/mol) are in 2 moles of NaCl?

Answer: 117 g

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

Which of the following is an example of a synthesis reaction?

Answer: 2Na + Cl₂ → 2NaCl

A synthesis reaction combines two or more substances into one product; 2Na + Cl₂ → 2NaCl is a classic example.

If 10 g of hydrogen reacts with excess oxygen, and the molar mass of H₂ is 2 g/mol, how many moles of H₂ are present?

Answer: 5 moles

Moles = mass ÷ molar mass = 10 g ÷ 2 g/mol = 5 moles.