A solution of sodium hydroxide is standardized against potassium hydrogen phthalate. From the fo

A solution of sodium hydroxide is standardized against...

Key Concepts

Acid-Base Titration

Acid-base titration is an analytical method used to determine the concentration of an unknown acid or base solution by reacting it with a solution of known concentration. The point at which the reaction is exactly complete, called the equivalence point, marks the stoichiometrically equivalent amounts of acid and base, which is pivotal in calculating unknown concentrations.

Standardization

Standardization is the process of determining the exact concentration of a titrant solution by using a primary standard – a substance of known purity and stability. This step is vital in analytical chemistry to ensure that volumetric analyses provide accurate and reliable results.

Primary Standard

A primary standard is a highly pure, stable, and non-hygroscopic compound used to accurately determine the concentration of a solution in titrations. Its known molar mass and reactivity allow it to serve as a benchmark against which the titrant’s concentration is adjusted.

Stoichiometry

Stoichiometry is the quantitative relationship between reactants and products in a chemical reaction, defined by a balanced chemical equation. It allows for the calculation of moles and the subsequent determination of concentrations, which is fundamental in titration analyses.

Molarity

Molarity is a concentration unit defined as the number of moles of a solute per liter of solution. It is a key concept in analytical chemistry, especially in titration procedures, since calculating molarity accurately is critical for quantifying the properties of chemical solutions.

Transcript

00:01 In this question, we need to determine the malarity of sodium hydroxide that's being standardized against a certain mass of potassium hydrogen thallate.

00:14 Now, potassium hydrogen thallate can be abbreviated by khp.

00:22 So i'm going to use the abbreviation most of the time when i talk about potassium hydrogen thalate.

00:27 But i've used the complete formula in the equation that i've written down here.

00:38 So this is khp, that is the abbreviation of potassium hydrogen thallate.

00:48 Now, the mass of the khp is given, and then also the volume of the sodium nitroxide before titration started.

00:58 And then once the titration is done.

01:02 So i still need to calculate the total volume of sodium hydroxide that was used for this standardization.

01:14 And this i can do by saying the final volume, 37 .26 millimeters minus the initial volume of 0 .233 milliliters.

01:27 And this gives a value of 37 .37 .3 .0 .0 .03 .03mm .03mm.

01:42 Right.

01:45 So i'm going to use that volume as the volume of sodium nitroxide that was used during this standardization.

01:53 Now, for a standardization, it means, actually means that the sodiumide, hydroxide reacts with the k -hp according to the stoichiometric ratio of this reaction.

02:08 And the stoichiometric ratio here of sodium hydroxide to k -hp is one -to -one.

02:17 The reaction is balanced as it is.

02:21 So for us in order to use the stoichiometric ratio, we need to work with number of moles.

02:28 So the first thing would be here to convert the mass of khp to the number of moles of khp.

02:40 And then i can use my stochymetric ratio of 1 to 1 to determine the number of moles of sodium hydroxide, which will just actually be the same because of the 1 to 1 mole ratio here.

02:53 And then once i have the number of moles of sodium hydroxide, it's going to be easy to calculate.

02:59 Molecularity because i already have the volume of sodium hydroxide.

03:04 All right.

03:06 So for my first step here, i need to go and calculate the number of moles of khp, and that is going to be the mass of khp, 0 .5536 grams, divided by the molar mass of khp.

03:26 Now, instead of dividing by the molar mass, i can also multiply by, the reciprocal.

03:32 So the molar mass of khp is 204.

03:37 I'm just going to write it down here because i've pre -calculated it.

03:42 So the molar mass of khp is 204 .4 .2 grams per mole.

03:53 So instead of saying i divide by 204 .4 .2.

04:01 Grams per one mole, i can say i multiply with a reciprocal.

04:05 So it's per, it's one mole at the top and then 204 .2 grams at the bottom.

04:13 So instead of saying divide by 204 .2 grams per mole, i say i multiply with the reciprocal, which is one mole over 204 .2 grams.

04:28 Right...