chem lab final

01 Conductance

Ability of a solution to conduct electricity

01 Resistance

Opposition offered to current flow

01 Specific conductance

Conductance of solution of unit length and unit area

01 Conductivity

Conductance per unit length and cross-sectional area

01 Electrolyte

Substance producing ions in solution

01 Strong electrolyte

Completely ionized electrolyte

01 Weak electrolyte

Partially ionized electrolyte

01 Conductometric titration

Titration using conductance measurements to determine endpoint

01 Equivalent point

Point where acid and base react completely

01 Endpoint

Point detected experimentally indicating completion

01 Ion mobility

Speed of ion movement in electric field

01 Cell constant

Ratio of distance between electrodes to electrode area

01 Conductivity cell

Apparatus used to measure conductance

01 Neutralization

Reaction between acid and base producing salt and water

01 Strong acid

Acid completely ionizing in water

01 Strong base

Base completely ionizing in water

01 Specific resistance

Resistance of unit cube of solution

01 Molar conductance

Conductance of solution containing one mole of electrolyte

01 What is the principle of conductometric titration?

Conductance changes due to replacement of ions with different mobility during titration.

01 What is the principle of this experiment?

H⁺ ions are replaced by Na⁺ ions during neutralization causing conductance variation.

01 What reaction occurs in this experiment?

HCl reacts with NaOH to form NaCl and water.

01 What is measured in conductometry?

Conductance of solution.

01 Why does conductance change during titration?

Ionic composition changes during reaction.

01 Why is HCl used?

Because it is a strong acid and ionizes completely.

01 Why is NaOH used?

Because it is a strong base and ionizes completely.

01 Why does HCl conduct electricity?

Due to presence of H⁺ and Cl⁻ ions.

01 Why does NaOH conduct electricity?

Due to Na⁺ and OH⁻ ions.

01 Why does conductance decrease initially?

H⁺ ions are replaced by less mobile Na⁺ ions.

01 Why does conductance increase after endpoint?

Excess OH⁻ ions increase conductivity.

01 Why is H⁺ highly mobile?

Due to proton hopping mechanism.

01 Why is OH⁻ highly mobile?

Due to rapid proton transfer in water.

01 Why is Na⁺ less mobile?

It moves physically through solution unlike proton hopping.

01 Why does the graph become V-shaped?

Conductance first decreases then increases after endpoint.

01 Why is minimum conductance observed near endpoint?

Highly mobile H⁺ ions are fully neutralized.

01 Why are platinum electrodes used?

Platinum is inert and good conductor.

01 Why are electrodes dipped completely?

For proper electrical contact.

01 Why should air bubbles be avoided?

They reduce effective electrode area.

01 Why is no indicator used?

Endpoint is determined by conductance measurement.

01 Why is conductometric titration suitable for colored solutions?

Color does not affect conductance.

01 Why is stirring necessary?

To ensure uniform mixing.

01 Why should NaOH be added slowly?

To obtain accurate endpoint.

01 Why should temperature remain constant?

Conductance depends on temperature.

01 Why does temperature affect conductance?

Higher temperature increases ion mobility.

01 Why is distilled water used?

To avoid extra ions.

01 Why should apparatus be rinsed?

To prevent contamination.

01 Why is burette rinsed with NaOH?

To avoid dilution error.

01 Why is conductivity cell cleaned before use?

Deposits affect readings.

01 Why is endpoint determined graphically?

Graph gives accurate equivalence point.

01 Why are strong electrolytes better conductors?

They produce more ions.

01 Why is pure water poor conductor?

Very few ions are present.