6. Quantitative Chemistry Flashcards
What is the principle of conservation of mass in chemical reactions?
No atoms are lost or made during a chemical reaction, so the mass of the products equals the mass of the reactants.
How can the masses of reactants and products be calculated?
The masses of reactants and products can be calculated from balanced symbol equations.
Why might it not be possible to obtain the calculated amount of a product?
Because the reaction may not go to completion, some product may be lost during separation, or some reactants may react in unexpected ways.
What is the relative formula mass (Mr) of a compound?
The relative formula mass (Mr) is the sum of the relative atomic masses of the atoms in the numbers shown in the formula.
How is the percentage by mass of an element in a compound calculated?
It is calculated from the relative atomic mass of the element and the relative formula mass of the compound.
What can be calculated from the masses or percentages of elements in a compound?
The empirical formula of the compound.
What is one mole of a substance?
The relative formula mass of a substance, in grams, is known as one mole of that substance.
What is Avogadro’s constant?
One mole contains 6.02 × 10^23 atoms or molecules.
How is the concentration of a solution calculated?
Concentration (mol/dm3) = number of moles / volume of solution (in dm3).
How can the volumes of acid and alkali solutions that react be measured?
By titration using a suitable indicator.
What can titration results be used for if the concentration of one reactant is known?
To find the concentration of the other reactant.
What is the molar gas volume at room temperature and pressure?
24 dm3.
