Quantitative Chem 1 Flashcards
(17 cards)
How do you calculate moles from mass and Mr?
Moles = Mass (g) ÷ Mr.
How do you calculate mass from moles and Mr?
Mass = Moles × Mr.
How do you calculate Mr from mass and moles?
Mr = Mass ÷ Moles.
What are the units for mass, Mr, and moles?
Mass in g, Mr is unitless, moles in mol.
What is the law of conservation of mass?
Mass is neither created nor destroyed in a chemical reaction.
Why might mass appear to increase in a reaction?
Because a gas is taken in from the air (e.g., oxygen).
Why might mass appear to decrease in a reaction?
Because a gas is released and escapes (e.g., CO₂).
How can you check mass is conserved in an equation?
Total Mr of reactants equals total Mr of products.
What is a limiting reactant?
The reactant that is completely used up first in a reaction.
What is an excess reactant?
The reactant that is not fully used up in a reaction.
Why do chemists use moles in equations?
To calculate the amounts of substances involved.
What is the mole ratio?
The ratio of moles of substances in a balanced chemical equation.
How do you find the limiting reactant in a reaction?
Compare the number of moles available for each reactant with the balanced equation.
What is percentage yield?
(Actual yield ÷ Theoretical yield) × 100.
What is theoretical yield?
The maximum mass of product expected based on the balanced equation.
Why is actual yield usually less than theoretical yield?
Due to loss during transfer, side reactions, or incomplete reactions.
What are common reasons for mass changes in reactions?
Gas entering or leaving, not all reactants reacting, product lost during separation.
