anachem terms

Steps in Qualitative Analysis

Sample is dissolved in water → Sample Solution with analyte separates into Ions → Separation and Isolation of Analyte → Individual Ions is isolated → Confirmative Test for the Identity of the Ion → identification of Ion by color response and formation of a precipitate

one at a time

Ionization of H+ from an acid occurs ______________

1. Dissolving and Precipitation Reaction

2. Ionization Reaction

Two Main Reactions in Qualitative Analysis

Dissolving and Precipitation Reactions

needed for the initial step done on the sample and the succeeding steps for separation and isolation of ions

Sample or substance is slightly soluble in water

problem encountered for dissolving and precipitation reaction

Ionization Reaction

Refers to the separation of a substance (analyte) into ions

Substance (analyte) is partially ionized when dissolved in water

problem encountered for ionization reaction

Equilibrium Condition

determines the amount of solid dissolved when it is slightly soluble

Equilibrium Condition

determines the amount of ions formed when it is partially ionized

General Type of Reversible Reaction

May be a homogenous reversible reaction or a heterogenous reversible reaction

General Type of Reversible Reaction

𝑎𝐴 + 𝑏𝐵 ⇌ 𝑐𝐶 + 𝑑𝐷 is what kind of equilibrium condition?

𝐾𝑒𝑞

equilibrium constant symbol

Dissolving and Precipitation

equilibrium condition For Heterogenous Reversible Reaction

Dissolving and Precipitation

𝑨𝒙𝑩𝒚 ⇌ 𝒙𝑨 +𝒚 (𝒂𝒒) + 𝒚𝑩 −𝒙 (𝒂𝒒) is the equation for:

Ksp

Solubility product constant symbol

Ionization Reaction

Equilibrium Condition Reaction of Homogenous Equilibria (For homogenous reversible reaction)

Ionization Reaction

𝐇𝐀 ⇌ H +(𝒂𝒒) + OH−(𝒂𝒒) is the equation for:

Ki = Ka = Kb

Ionization Constant symbol

Equilibrium between H+ and OH-

Reaction in any aqueous solution

Equilibrium between H+ and OH-

𝐇𝟐𝐎 ⇌ H + + OH is the equation for:

1x10^-14

Ion-Product Constant of water

Acidic

A solution has 0.41M of H and 0.32M OH, is this solution acidic or basic?

basic anions

salts whose anions are proton acceptors

Basic

A solution has 0.55M of OH and 0.42M H, is this solution acidic or basic?

Non-Electrolytes & Electrolytes

2 Kinds of Solutes based on the Extent of Ionization

Non-Electrolytes

Solutes that will not separate into ions when dissolved in water. Refer to covalent compounds (mostly organic compounds)

Electrolytes

Solutes that separates into ions when dissolved in water. Refer to ionic compounds (mostly inorganic compounds)

weak and strong electrolytes

2 kinds of electrolytes

Strong electrolytes

completely separate into ions. Ex. Strong acids, strong bases, salts

Weak Electrolytes

partially/incompletely separate into ions Ex. Weak Acids, weak bases

Solubility product principle

The product of the molar concentration of the ions produced from the portion of the solid solute dissolved at equilibrium/saturation each raised to exponents equal to their coefficients in the balanced chemical equation is equal to the Ksp value – solubility product constant.

Solubility

Refers to the maximum amount of solute that can be dissolved in a given amount of solvent or solution at equilibrium

[𝑨 +] 𝒙 [𝑩 −] 𝒚 < 𝑲𝒔p // solubility value is less than Ksp value

• Conditions occurring in the mixture containing AxBy:

  • Solution is unsaturated

  • more AxBy can still dissolve in the solution

  • No precipitation occurs

[𝑨 +] 𝒙 [𝑩 −] 𝒚 = 𝑲𝒔𝒑 // Solubility is equal to Ksp value

• Conditions occurring in the mixture containing AxBy:

  • Solution is saturated

  • It is About to start precipitation when any excess of AxBy is added.

[𝑨 +] 𝒙 [𝑩 −] 𝒚 > 𝑲𝒔p
Solubility is greater than Ksp value

• Conditions occurring in the mixture containing AxBy:

  • Not Possible

  • Mixture is heterogenous with precipitate formed.

Ionization Reaction

Involves the separation of an electrolyte (ionic compound)

Irreversible Ionization Reaction

Refers to the complete ionization reaction of strong electrolytes (strong acids, strong bases, and almost all salts)

Reversible Ionization Reaction

Refers to the complete ionization or partial ionization of weak electrolytes (weak acids and weak bases) into ions. Common Types of weak acids found in the Ka-Table.

Inorganic weak base (NH3 or NH4OH) and organic weak bases (amine or amino compound)

common types of weak bases

Percentage/Fractional Ionization

Measure of the extent of ionization undergone by a weak electrolyte

p-value

used to express exponential values into an “almost” whole number value and eliminates the inconvenience of using exponential values

pH and pOH

measures of the molar concentration of H+ and OH- present in the solution

pH and pOH

measures the acidity and basicity of the solution

buffer solutions

contains a mixture of weak electrolytes with corresponding salt

buffer solutions

can resist changes in the pH even when strong acid/base is added

buffer solution

involves application of “common-ion effect” under the Le Chatelier’s Principle

Le Chatelier’s Principle

states that “If a stress/disturbance is applied to a system (reversible reaction) at equilibrium, the system will momentarily shift to a direction to regain equilibrium.”

• Concentration

• Temperature

• Pressure

Stress/Disturbances affecting EQ conditions

Neutral ions

a kind of salt whose ions are aprotic, with no reaction to water ex. NaCl, KCl, Na2SO4

acidic cations

Kinds of salt whose cations are proton-donor

sampling

involves obtaining a sample to be taken for analysis to be taken for analysis whose composition is representative of the whole batch of the original material

qualitative analysis

this type of analysis aims to reveal the chemical identity of the species present in a sample

analytical chemistry

a branch of chemistry concerned with the separation, identification, and determination of relative amounts or purity of components or constituents in an unknown sample of matter

analyte

this is the sought for component or desired component

analysis

refers to the laboratory technique conducted to identify the components or analytes present in a sample

assay

the process of determining how much of a given component or analyte is present in a given sample, this is commonly used for metal or ore samples

quantitative analysis

aims to determine the relative amounts or purity of one or more species or components or analytes in a sample

stoichiometric methods

amount of analyte in the sample is computed through the use of stoichiometric relationships

volumetric or titrimetric methods

amount or purity of analyte is computed from the measured volume and known concentration of a solution made to completely react with the analyte

gravimetric methods

amount or purity of the analyte is computed from the measured mass of a converted weighable substance derived from the analyte

non-stoichiometric methods

also known as instrumental methods, makes use of a readily measurable physical char. or other properties of the analyte eg. colorimetry, spectrophotometry

dissolved in water

sample containing the analyte is always ____________ to form a solution

solution

another term for a homogenous mixture

solute

components present in lesser amount or the one that is being dissolved in solution

solvent

component present in greater amount of the one that is capable of dissolving the other component

concentration of solution

refers to the quantity that specifies or gives the measure of the amount of solute present in solution or dissolved in the solvent

unsaturated solution

solute in solution is less than the maximum amount that can be dissolved in a solution

saturated solution

contains the maximum amount of solute that can possibly dissolve in a solution

supersaturated solution

actual amount of solute dissolved in solution is more than the maximum amount that can be dissolved in the solution

solubility

maximum amount of solute that can be dissolved in a given amount of solvent

dilute solution

a weaker acid/base solution with lesser acid/base-content

concentrated solution

a stronger acid/base solution with greater acid/base content

dilution

process of adding more solvent (water) to a solution in order to decrease its concentration. One of the methods in preparing solutions

water

universal solvent

volumetric / titrimetric methods

a quantitative chemical analysis performed by measuring the volume of a certain solution with accurately-known concentration needed to completely react with the desired constituent or analyte in the sample

standard solution

solutions that are prepared with accurately known concentration

indicators

substances that impart two different colors when placed in solution with different medium

titration

the process of reacting a substance in solution with another substance in solution

standard solution

a solution with an accurately known concentration usually in normality

titrant/titrating agent

the standard solution used in reacting with the analyte in the sample. Solution is placed in the burette

titrant

solution in the erlenmeyer flask, also known as the analyte

indicator

a substance which is capable of imparting two shades of color when subjected to different media solutions

equivalence point

a stage in a reaction between two substances wherein the amount of substances used up in the reaction are just exactly enough according the the stoichiometric amounts needed in order for the reaction to be completed

endpoint

a stage in titration wherein there is a color change of the indicator

neutralization methods

involve reaction between acidic and basic components

redox methods

involve analyte and titrant capable of undergoing oxidation reduction reaction

acid, base

for acidimetry, analyte = ? and standard solution = ?

alkalimetry

for alkalimetry, analyte = ?, standard solution = ?