Calculate the concentration of all species in a 0.155 M solution of H2 CO3 .

Name: Problem 114, Chapter 16: Chemistry A Molecular Approach
Uploaded: 2020-02-24T00:40:47-08:00
Duration: 6 min 45 s
Channel: Ahmed Ali
Description: Calculate the concentration of all species in a 0.155 M solution of H2 CO3 .

Calculate the concentration of all species in a 0.155 M...

Key Concepts

Equilibrium Constant Expression

The equilibrium constant expression is derived from the balanced chemical equation for the dissociation reaction. It relates the concentrations of the reactants and products at equilibrium. Setting up the correct expression is essential for solving the concentrations of different species in a weak acid solution.

Mass and Charge Balance

Mass and charge balance equations are constraints that ensure the total amounts of atoms and charges in the solution remain constant. They are used in conjunction with the equilibrium expression to solve for unknown concentrations in the system, ensuring that all species in a closed system are accounted for.

Acid Dissociation Constant (Ka)

The acid dissociation constant, Ka, quantifies the extent of dissociation of a weak acid in solution. It is defined by the ratio of the concentrations of the products (proton and conjugate base) to the concentration of the undissociated acid at equilibrium. The magnitude of Ka indicates how strong or weak the acid is, with smaller values corresponding to less dissociation.

Acid-Base Equilibrium

Acid-base equilibrium refers to the reversible ionization of acids in water, where a weak acid only partially dissociates into its conjugate base and hydronium ions. This balance between the undissociated acid and its ionized forms is governed by the acid’s dissociation constant (Ka), and it is crucial for predicting the concentrations of various species in solution.

Stepwise Dissociation in Polyprotic Acids

Polyprotic acids, such as carbonic acid, can donate more than one proton sequentially. Each dissociation step has its own equilibrium and Ka value. Understanding stepwise dissociation is important because each ionization step alters the equilibrium concentrations and affects the overall speciation in the solution.

Transcript

00:01 Everyone my name is ahmad ali in this question we have carbonic acid this carbonic acid has concentration is 0 .155 molarity we want to know when this compound dissolved in water we want to calculate the concentration of each species exists in water so first of all when this compound dissolved in water it ionized which we one proton from carbonic go to the water to leave the carbonic as a bicarbonate and for hydronic but not all carbonic will ionize the proton which only small amount of am which is x that ionized to the proton depending on its k a1 value so now according to create a1 value which is equal 4 .3 times by timbauer negative 7 which is means that small amount of carbonic acid will ionize.

01:17 Okay, so now if we want to write the k equation, it will be the concentration of the product time each other, divided by the remaining concentration of carbonic, so if you write it by the concentration, it will be x times x, so x squared, divided by 0 .155 negative to x and due to the value of ka is very small so x is neglected comparing to the initial value to be the calculation of x is equal the root of 0 .155 times by 4 .3 times by 10 power negative 7.

02:05 To be the result 2 .6 times by timbauer negative 4.

02:12 So now if we remove this and remove this and remove this we will put here the concentration is 2 .6 times by team over negative 4 the concentration of this 2 .6 times by 10 negative 4 and here we say 0 .155 negative to 2 .6 times by tim power negative 4.

02:41 Here comparing to 0 .15 we can neglect it.

02:46 So we can neglect this to be the concentration of carbonic is 0 .155.

02:55 Then this by carbonate a small amount of a transferable proton to water to form co3 negative 2 plus h 3 or positive...

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