3.1.2.3 The ideal gas equation & 3.1.2.4 Empirical and molecular formula

What is the ideal gas equation?

PV = nRT, where P is pressure, V is volume, n is moles, R is the gas constant, and T is temperature.

What are potential errors in using a gas syringe?

Gas escaping before bung is inserted, syringe sticking, and some gases being soluble in water.

What is the relationship between equal volumes of gases at the same temperature and pressure?

They contain equal numbers of molecules.

What volume does 1 mole of any gas occupy at room temperature and pressure?

24 dm³

What is the molar volume of gas at standard conditions?

22.4 liters (or 22.4 dm³) at 0°C and 1 atm.

How do you convert Celsius to Kelvin?

To convert Celsius to Kelvin, add 273.

What is the effect of temperature on gas pressure? /

Increasing temperature increases pressure if volume is constant.

What is an empirical formula?

An empirical formula is the simplest integer ratio of atoms of each element in a compound.

What is the general method for calculating an empirical formula?

1. Divide each mass (or % mass) by the atomic mass of the element.

2. Divide each result by the smallest number obtained.

3. Multiply to get whole numbers if necessary.

What is a molecular formula?

A molecular formula is the actual number of atoms of each element in a compound.

How do you determine the molecular formula from the empirical formula?

Divide the relative molecular mass (Mr) by the mass of the empirical formula to find how many times the empirical formula fits into the Mr.

WORKED EXAMPLE

If you have 0.400 mol dm⁻³ of MgCl2, how many moles of chloride ions are present?

There are 0.800 moles of chloride ions, as there are two chloride ions for every mole of MgCl2.

What happens when soluble ionic solids dissolve in water? Why does this matter?

They dissociate into separate ions. SO the ion concentrations CAN differ to solute’s concentrations, i.e;

MgCl2(s) +aq → Mg2+(aq) + 2Cl-(aq)

0.1 mol 0.1 mol 0.2 mol

IF substance doesnt dissolve well in beaker

the beaker and its contents could be heated gently until all the solid had dissolved

What is the process for making a solution from a solid?

Weigh the solid, dissolve in water, and make up to the mark in a volumetric flask.

What is the dilution process of a solution using a volumetric pipette?

Pipette a specific volume of the original solution and dilute with distilled water.

What safety precautions should be taken when handling hazardous substances?

Wear goggles, gloves, and avoid skin contact.

Diluting a solution effect on moles, concentration and volume:

will not change the amount of moles of solute present increase the volume of solution

the concentration will lower

What is the significance of the meniscus in volumetric measurements?

The bottom of the meniscus should sit on the line for accurate measurement.

What is the significance of the limiting reactant in a chemical reaction?

It determines the maximum amount of product that can be formed.