# We are aiming to accurately prepare a standard solution of 0.1 M (mol dm-3) sodium carbonate; this solution will then be used to calculate the concentration of a hydrochloric acid solution

by keesha_andre (student)

Serena Wright

Gardner

Titration

Aim

A common practise carried out in the laboratory is to accurately prepare chemical solutions.

We are aiming to accurately prepare a standard solution of  0.1 M (mol dm-3) sodium carbonate; this solution will then be used to calculate the concentration of a hydrochloric acid solution.

Background

The most convenient ways to express concentration is in:

g dm-3  grams per cubic decimetre or grams per litre

mol dm-3 the number of moles per cubic decimetre

For measuring accurately, you will use equipment like pipettes, burettes and volumetric flasks.

Experiment 1

Making a solution of sodium carbonate (alkali) by weighing

Below is the standard procedure that I followed I copied and pasted it into my work:

Calculate the mass of sodium carbonate needed, m1.

Weigh a clean weighing bottle, and record its mass, m2. (See figure a)  With a clean spatula, add pure anhydrous sodium carbonate until the combined mass of weighing bottle and sodium carbonate = m1+m2.

Transfer the sodium carbonate carefully into a clean beaker.  (See figure b)  Use a washed bottle of distilled water so that all the washings run into the beaker.  Add about 100 cm3 of distilled water.  Stir with a glass rod until the entire solid has dissolved.  (See figure c)

Pour all the solution carefully through a filter funnel into a graduated flask (see figure d).  Wash all the solution out of the beaker and off the glass rod (see figures e, f)

Add distilled water until the level is about 2cm below the graduation mark on the graduated flask.  Add the rest of the distilled water drop by drop from a dropping pipette until the bottom of the meniscus is level with the graduation mark when viewed at eye level (see figure g).  Insert the stopper of the flask and invert the flask several times to mix the solution (see figure h)

Safety

Sodium carbonate is an irritant

Wear goggles

Adaptation to standard procedure:

The first thing that we changed was point number 2; we put the weighing bottle on the scales, and zeroed the scales. This is making m2 (weighing bottle) effectively zero.

The volumetric flask we were given was not 110cm3, it was 250cm3, and so we had to make up 250cm3 of 0.1-mol dm-3 sodium carbonate.

Calculating m1- the mass of sodium carbonate needed, m1.

To find the mass of sodium carbonate (Na2CO3) we need to find its molecular mass.

To calculate the molecular mass of Sodium Carbonate = Na2CO3

Making a 0.1 M (mol dm-3) solution of sodium carbonate in 1000 cm3

A 1 M (mol dm-3) solution of sodium carbonate (Na2CO3 ) means: -106 g of sodium carbonate is dissolved in a cubic decimetre (1000 cm3).                                     ...