Topic 3 Stoichiometry Flashcards
(31 cards)
What does the molecular formula show?
The number and type of different atoms in one molecule.
What is the empirical formula?
The simplest whole number ratio of the different atoms or ions in a compound.
How do you find the molecular formula from the empirical formula?
Molecular Formula = n × (Empirical Formula), where n = Molar Mass ÷ Empirical Formula Mass.
How do you deduce the formula of a simple molecular compound?
By using the relative number of atoms in a model or diagram.
How do you deduce the formula of an ionic compound?
From the charges on the ions or from a model showing their ratio.
What is needed for a word equation?
Show how reactants form products.
When is a symbol equation balanced?
When there are equal numbers of atoms and charges on both sides.
What are the four state symbols in chemical equations?
(s) = solid, (l) = liquid, (g) = gas, (aq) = aqueous solution.
What ending do compounds have if they contain only two elements?
“-ide” (e.g., Sodium chloride).
What ending do compounds have if they contain oxygen?
-ate” (e.g., Sulfate, Nitrate).
What is relative atomic mass (Ar)?
The average mass of an element’s isotopes compared to 1/12th the mass of a carbon-12 atom.
What is relative molecular mass (Mr)?
The sum of relative atomic masses of all atoms in one molecule.
What is a mole?
The amount containing 6.02 × 10²³ particles (atoms, ions, molecules).
What is Avogadro’s constant?
6.02 × 10²³ particles per mole
How much volume does 1 mole of gas occupy at room temperature and pressure (r.t.p.)?
24 dm³.
What is the formula to find the number of moles using mass?
Moles = Mass ÷ Molar Mass.
What is the formula for moles in solution?
Moles = Concentration × Volume (in dm³).
How do you convert cm³ to dm³?
Divide by 1000.
How do you find the volume of gas at r.t.p.?
Volume = Number of Moles × 24 dm³.
How can concentration be measured?
In mol/dm³ or g/dm³.
How to convert concentration from mol/dm³ to g/dm³?
Multiply by molar mass.
What is the formula for moles in acid-base titration?
Moles = (Concentration × Volume) ÷ 1000.
What is the formula for percentage composition by mass?
(Mass of element ÷ Molecular mass) × 100.
What are the steps to calculate percentage composition by mass?
1.Find molar mass
2.Find mass of specific element
3.Apply formula
4.Multiply by 100
