Atoms, Molecules & Stoichiometry

Flashcards for Cambridge (CIE) AS Chemistry - Reacting Masses & Volumes, Formulas, The Mole & the Avogadro Constant, and Relative Masses of Atoms & Molecules.

How do you calculate the number of moles?

mass of a substance (g) / molar mass (g mol⁻¹)

How do you calculate percentage yield?

(actual yield / predicted or theoretical yield) x 100

How do you calculate concentration (mol dm⁻³)?

number of moles of solute (mol) / volume of solution (dm³)

What is a key characteristic of ionic compounds regarding their electrical charge?

Ionic compounds are electrically neutral; the positive charges equal the negative charges.

What are the common charges of metals in Group 1, Group 2, and Group 13?

Metals in Group 1, Group 2, and Group 13 have charges of 1+, 2+, and 3+ respectively.

Why are Roman numerals used with some compounds of transition elements?

Transition elements can have varying charges, indicated by Roman numerals.

What is a common characteristic of non-metal ions in Group 15 to 17?

Non-metals in Group 15 to 17 have a negative charge and typically end with the suffix 'ide'.

What is a symbol equation?

A symbol equation is a shorthand way of describing a chemical reaction using chemical symbols.

What fundamental principle is applied when balancing chemical equations?

Atoms cannot be created or destroyed, so the number of each atom on each side of the reaction must be the same.

What does the state symbol (s) represent?

Solid

What does the state symbol (l) represent?

Liquid

What does the state symbol (g) represent?

Gas

What does the state symbol (aq) represent?

Aqueous

What are spectator ions?

Ions that do not participate in a reaction.

What does an ionic equation show?

Shows only the ions or particles taking part in a reaction, without spectator ions.

What is the empirical formula?

The simplest whole number ratio of elements in a compound.

What is the molecular formula?

The number and type of each atom in a molecule.

What is compound called when it contains water of crystallization?

Hydrated compound.

What is a compound called which doesn't contain water of crystallisation?

Anhydrous compound.

Hydrated copper(II) sulfate is heated to form anhydrous copper(II) sulfate, what is the reaction equation?

CuSO4.5H2O = CuSO4+5H2O

What is the Avogadro constant?

The number of particles equivalent to the relative atomic mass or molecular mass of a substance.

What is the value of the Avogadro constant (NA)?

6.02 x 10^23 mol-1

What is a mole (mol)?

The mass of a substance containing the same number of fundamental units as there are atoms in exactly 12.00 g of 12C.

How is relative atomic mass calculated?

Σ (isotope percentage abundance * isotope mass number) / 100

What is relative molecular mass (Mr)?

Weighted average mass of molecules in a sample.