Stoichiometry Lecture Flashcards

Comprehensive practice flashcards covering key stoichiometry concepts, valencies, ionic equations, mole calculations, empirical/molecular formulas, percentage yields/purities, and solution concentrations.

How is valency determined for elements in Periodic Table Groups I through IV?

For elements in Groups I to IV, $\text{Valency} = \text{group number}$.

How is valency determined for elements in Periodic Table Groups V through VII?

For elements in Groups V to VII, $\text{Valency} = 8 - \text{group number}$.

What is the valency of elements in Group VIII (Group 0)?

Elements in Group VIII/0 have a valency of $0$.

What are the chemical formula, valency, and charge of the Carbonate ion?

The formula is $\text{CO}_3^{2-}$, the valency is $2$, and the charge is $2-$.

What are the chemical formula, valency, and charge of the Sulfate ion?

The formula is $\text{SO}_4^{2-}$, the valency is $2$, and the charge is $2-$.

What are the chemical formula, valency, and charge of the Nitrate ion?

The formula is $\text{NO}_3^{-}$, the valency is $1$, and the charge is $1-$.

What are the chemical formula, valency, and charge of the Ammonium ion?

The formula is $\text{NH}_4^{+}$, the valency is $1$, and the charge is $1+$.

What is the formula for ammonium sulfate using compound ions?

The formula for ammonium sulfate is $\text{(NH}_4\text{)}_2\text{SO}_4$.

Which non-metal elements must always be written as diatomic molecules in chemical equations?

The non-metals that must be written as molecules are $\text{H}_2$, $\text{N}_2$, $\text{O}_2$, $\text{F}_2$, $\text{Cl}_2$, $\text{Br}_2$, and $\text{I}_2$.

What do the chemical state symbols (s), (l), (g), and (aq) represent?

$(s)$ represents solid, $(l)$ represents liquid, $(g)$ represents gas, and $(aq)$ represents aqueous solution.

What is an ionic equation and what are spectator ions?

An ionic equation shows only those ions and molecules taking part in the reaction. Spectator ions are ions that do not take part in the reaction.

What is the net ionic equation for the reaction of magnesium with dilute sulfuric acid?

The net ionic equation is $\text{Mg}(s) + 2\text{H}^{+}(aq) \rightarrow \text{Mg}^{2+}(aq) + \text{H}_2(g)$.

What is the definition of relative atomic mass (Ar)?

Relative atomic mass ($A_r$) is the average mass of naturally occurring atoms of an element on a scale where a carbon-12 atom has a mass of exactly $12$ units.

What is a mole and what is the value of the Avogadro Constant (L)?

A mole is the amount of substance that contains $6.02 \times 10^{23}$ atoms, molecules, or ions. The Avogadro Constant ($L$) is $6.02 \times 10^{23}$.

What formula relates mass, number of moles, and molar mass?

$$\text{Number of moles} = \frac{\text{mass}}{\text{molar mass}}$$

What volume does 1 mole of any gas occupy at room temperature and pressure (r.t.p)?

At room temperature and pressure, $1\text{ mole}$ of any gas occupies $24\text{ dm}^3$ (or $24\text{ liters}$).

What is the formula for finding the volume of a gas at room temperature and pressure (r.t.p)?

$$\text{Volume (dm}^3\text{)} = \text{moles} \times \text{molar volume}$$

What is a limiting reactant?

The limiting reactant is the reactant that is not in excess. It is used up first, causing the reaction to stop.

What is the difference between an empirical formula and a molecular formula?

An empirical formula shows the simplest whole-number ratio of atoms present in a compound, whereas a molecular formula shows the actual number of atoms of each element present in a molecule.

How is percentage yield calculated?

$$\text{Percentage yield} = \frac{\text{Actual yield}}{\text{Predicted yield}} \times 100$$

How is percentage purity calculated?

$$\text{Percentage purity} = \frac{\text{mass of pure substance}}{\text{mass of impure substance}} \times 100$$

What is the formula for solution concentration in mol/dm³ using volume in dm³?

$$\text{Concentration (mol/dm}^3\text{)} = \frac{\text{number of moles of solute (mol)}}{\text{volume of solution (dm}^3\text{)}}$$

How is solution concentration expressed in g/dm³ calculated?

$$\text{Concentration (g/dm}^3\text{)} = \frac{\text{mass of solute (g)}}{\text{volume of solution (dm}^3\text{)}}$$