A 0.06 M standard solution of sodium carbonate was made up by weighing out X grams of anhydrous sodium carbonate (Na2CO3), dissolving it in deionised water, and making the solution carefully up to the mark in a suitable 1 litre flask - Leaving Cert Chemistry - Question 2 - 2006

A should be inverted. This is important to ensure that the solution is well mixed and homogeneous.

A standard solution is a solution whose concentration is known with high accuracy, which can be used for titration and calibration purposes.

To find the mass, we use the formula:

$X = M imes V imes M_w$

Where:

• M = molarity (0.06 M)
• V = volume (1 L) = 1000 cm³
• M_w = molar mass of Na2CO3 = 106 g/mol

Substituting the values:

$X = 0.06 imes 1000 imes 106 = 6.36 ext{ g}$

B is a pipette and C is a burette.

A suitable indicator is methyl orange. The colour changes from yellow to pink/orange to red.

The walls of the conical flask should be washed down with deionised water and swirled to ensure that all contents are mixed properly.

Using the titration data:

rac{25.0 ext{ cm}^3 imes 0.06 ext{ M}}{V_{ ext{HCl}}} = rac{30.0 ext{ cm}^3 imes C_{ ext{HCl}}}{1}

Letting the volume of HCl be the remaining volume, we deduce:

Based on stoichiometry, if 25.0 cm³ of Na2CO3 was required, the concentration of the HCl solution would be calculated to be:

$C_{ ext{HCl}} = 0.10 ext{ M}$