Free HSC Year 11 Chemistry Flashcard Review
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Define an element.
A pure substance made of one type of atom that cannot be broken down chemically.
Homogeneous vs heterogeneous mixture?
Homogeneous looks uniform throughout; heterogeneous has visibly different regions.
Which property does filtration use?
Difference in particle size (insoluble solid versus liquid).
Formula for percentage composition by mass?
(mass of component ÷ total mass) × 100.
How many neutrons in a nuclide with mass number A and atomic number Z?
A − Z (mass number minus atomic number).
Define isotopes.
Atoms of the same element with the same protons but different numbers of neutrons.
Why does a flame test give a coloured flame?
Excited electrons fall to lower levels and emit photons of specific energy, hence specific colours.
Electron configuration of sulfur?
1s² 2s² 2p⁶ 3s² 3p⁴.
Trend in first ionisation energy down a group?
Decreases, because the outer electron is further away and more shielded.
What shape is H₂O and is it polar?
Bent, with two lone pairs; polar.
Which intermolecular force is strongest?
Hydrogen bonding (H bonded to N, O or F).
Why does graphite conduct electricity?
Each carbon bonds to only three others, leaving delocalised electrons that move between layers.
State the law of conservation of mass.
Mass is neither created nor destroyed in a chemical reaction, so total reactant mass equals total product mass.
What is Avogadro's number?
6.022 × 10²³ particles per mole.
Write the formula linking moles, mass and molar mass.
n = m/M
How do you identify the limiting reagent?
Divide each reactant's moles by its coefficient; the smallest value is the limiting reagent.
Empirical versus molecular formula?
The empirical formula is the simplest ratio of atoms; the molecular formula is the actual number of atoms and is a whole-number multiple of it.
How is percentage composition of an element calculated?
(Mass of that element in one mole ÷ molar mass of compound) × 100.
What is the dilution equation?
c₁V₁ = c₂V₂, because the moles of solute stay constant.
What is a spectator ion?
An ion present in solution that does not take part in the reaction and is left out of the net ionic equation.