Experiment 5 Properties of Ionic and Covalent Compounds

EXPERIMENT 4 :

THE PROPERTIES PROPERTIES OF IONIC AND COVALENT COMPOUNDS Name : Matrix number : Group : Semester : Lecturer’s name :

Objective : To differentiate properties of ionic and covalent compounds based on the melting point, volatility and solubility.

Introduction : An ionic compound is a chemical compound in which ions are held together in a lattice structure by ionic bonds. Usually, the positively charged portion consists of metal cations and the negatively charged portion is an anion or polyatomic ion. Ions in ionic compounds are held together by the electrostatic forces between oppositely charged bodies. Ionic compounds have high melting and boiling points, and they are hard and very brittle. A covalent compound is a compound in which the atoms that are bonded share electrons rather than transfer electrons from one to the other. While ionic compounds are usually formed when metals bond to nonmetals, covalent compounds are formed when two non-metals bond to each other.

Apparatus and materials : 1. odium chloride crystals !. odium chloride solution "#$% &. 'en(ene ). *istilled water #. +aphthalene powder . +aphthalene solution "#% . /rucible 0. patula . 'unsen burner 12. Wire gau(e 11. Test tubes " ) per group% 1!. Tripod stand 1&. 3lass rod 1). 4vaporating dish

Results :

Sodium chloride

Naphthalene

Melting point

Solubility

White solid turns brown solid when heated gently. The sodium chloride produce ‘pop’ sound and the brown solid become dark brown when heated strongly

React with water  – the sodium chloride dissolve completely in water.

elts completely around !minute when heated

Volatility

Does not evaporates and it has low volatility

React with benzene – insoluble React with water  – does not dissolve in water and the suspended naphthalene "loated

#vaporates $uickly and it has high volatility.

React with benzene – dissolve completely

Discussion : In this e5periment, we as6ed to conduct an e5periment to observe the melting point, solubility and volatility of sodium chloride and naphthalene which is ionic and covalent compounds.

In the e5periment for melting point,a spatula of sodium chloride crystals are placed in a crucible and heated strongly.The changes in physical state are recorded.The e5periment for testing solubility of sodium chloride is carried out by putting sodium chloride crystals in two different test tubes which one containing # ml of ben(ene and the other one containing # ml of water respectively.Then,both test tubes are stirred with a glass rod and all observation are noted.The e5periment part for solubility and melting point are repeated for naphthalene.The e5periment for obtaining the volatility of ionic and covalent compound are conducted by placing ! drops of sodium chloride on an evaporating

dish while ! drops of naphthalene is placed on another evaporating d ish.The resuls are observed after 12 minutes.

The melting point of sodium chloride is higher than naphthalene is due to a stronger electrostatic force acted on oppositely-charged chloride ion and sodium ion present in sodium chloride.o,a lot of heat is re7uired to overcome this force of attraction resulting in high melting point.While,naphthalene has lower melting point because it only needs a small amount of heat to brea6 the wea6 van der waal8s force.

odium chloride is soluble in water instead of ben(ene because water is a polar molecule.9ence,The positive sodium ions and negative chloride ions will move to negative and positive region of water respectively.This will brea6 apart the sodium and chloride ions in their crystal lattice structure causing sodium chloride crystals to dissolve in water.While naphthalene dissolves in ben(ene because it tends to dissolve in non-polar solvent.

+aphthalene has higher volatility than sodium chloride solution because it has high volatile pressure.Thus,it will vapourise in a shorter time.While odium chloride solution has low volatile pressure which indicates longer time to vapourise than naphthalene.

:recaution steps must be ta6en to obtain an accurate result and avoid accident and in;ury.
onclusion : In conclusion, the sodium chloride which is ionic compound has higher intermolecular forces than covalent compound which is naphthalene that has lower intermolecular forces. This factor affect the melting point, solubility and volatility of the ionic and covalent compound.

!uestions : "# Give t$o examples o% ionic compounds and covalent compounds ot&er t&an t&ose used in t&is experiment# The other two e5amples of ionic compouds are lead "II% bromide and (inc nitrate. While the other e5amples of covalent compounds are methanol and ethanol.

'# (xplain )our results on meltin* point o% ionic compound and covalent compound as %ound in t&is experiment# In this e5periment, sodium chloride is one of e5ample of ionic compound used in this e5periment. It has strong electrostatic forces between the ions. o, a lot of of  energy are needed to overcome the forces and this causes the melting point of the sodium chloride which is ionic compound high. 'esides, naphthalene is one of the e5amples of the covalent compound. It has a wea6er =an *er Waals forces between the molecule. o less energy needed to overcome the forces and this causes the melting point of the covalent compound is low.

+# ,&) does nap&t&alene dissolve in or*anic solvents suc& as alco&ol and et&erbut does not dissolve in $ater. +aphthalene is a non-polar substance and only soluble in non-polar solvent such as alcohol and ether.

Re%erences : 1.

>aboratory manual

!.

http%&&en.wikipedia.org&wiki&'onic(compound

&.

http://wiki.answers.com/Q/What_is_covalent_compound_and_its_examples

4. 5.

  http://en.wikipedia.org/wiki/Volatility_(chemistry) www.chemtopic.com