Theme 3 - Stoichiometry Measurements Flashcards
(19 cards)
What is a solution composed of?
Solvent & solute
Solvent is the larger quantity, while solute is the substance dissolved in the solvent.
Define solvent.
Larger quantity in a solution
Define solute.
Substance dissolved in solvent
What is a true solution?
Mixture where solute molecules are distributed fairly in the solvent
Define concentration.
Amount of solute dissolved per unit volume in the solvent
What is molarity?
Molar concentration - number of moles per Litre
Molarity is used in stoichiometry to determine relative amounts of reactants and products in a chemical reaction.
What does percentage composition express?
Weight-to-volume percent (w/v %) - percent of solute mass to solvent volume
When is parts per million or parts per billion used?
For very dilute solutions
What is mass per volume used for?
Used for drug solutions and biochemistry - protein/nucleic acid solutions
What is the SI unit to measure the amount of a substance?
Mole
What does one mole contain?
As many elementary entities as there are atoms in 0.012 kg of carbon-12 ($^{12}C$)
What is Avogadro’s number?
Approximately 6.02 × 10^{23} particles in a mole
Define molecular weight.
Unitless measure of the mass of 1 mole of a substance
What is molar mass?
Mass of 1 mole of a substance in g mol^{-1}
How do you calculate the number of moles of a substance?
{Mass of substance} (m) ➗ Molecular weight (Mr)
Calculate the number of moles in 36g of H2O.
2 moles
Calculation: H ≈ 1 g/mol, O ≈ 16 g/mol; mol = {36}➗{16+1+1} = {36}➗{18}
What does molarity define?
Concentration of a solution in terms of the number of moles of a substance in 1L of a solution
What is the formula for molarity?
molarity (M) = number of moles (mol) / volume (L)
Calculate the molarity if there are 0.5 moles in 2.5L.
0.2 mol^{-1}
Calculation: Molarity = {0.5 mol}➗{2.5 L}
