KPK 9th Class Chemistry Chapter 8 Chemical Reactivity Short Questions Answers
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Class/Subject: 9th Class Chemistry
Chapter Name: Chemical Reactivity
Board: All KPK Boards
- Malakand Board 9th Class Chemistry Chapter 8 Chemical Reactivity short questions Answer
- Mardan Board 9th Class Chemistry Chapter 8 Chemical Reactivity short questions Answer
- Peshawar Board 9th Class Chemistry Chapter 8 Chemical Reactivity short questions Answer
- Swat Board 9th Class Chemistry Chapter 8 Chemical Reactivity short questions Answer
- Dera Ismail Khan Board 9th Class Chemistry Chapter 8 Chemical Reactivity short questions Answer
- Kohat Board 9th Class Chemistry Chapter 8 Chemical Reactivity short questions Answer
- Abbottabad Board 9th Class Chemistry Chapter 8 Chemical Reactivity short questions Answer
- Bannu Board 9th Class Chemistry Chapter 8 Chemical Reactivity short questions Answer
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KPK 9th Class Chemistry Chapter 8 Chemical Reactivity Short Questions Answers
Identify at least two group that contain only metallic atoms.
The two group of periodic table which just possess metal sare 1st group as;
| IA Group (Alkali Metals) | IIA Group (Alkaline Earth Metals) |
| Li | Be |
| Na | Mg |
| K | Ca |
| Rb | Sr |
| Cs | Ba |
| Fr | Ra |
Write down reactions of IA elements with oxygen with balance equation.
Behaviour with oxygen:
- All metals of this group burns in oxygen and form oxides (M2O)
- Li burns with red flame.
- Na burns with white flame.
- K burns with a little colored flame.
4Li+ 2O2→ 2Li2O
4Na+2O2→ 2Na2O
4K+ 2O2→ 2K2O
State the physical properties of metals.
The metals are generally consisted of the properties of:
- Hardness
- Brightness
- Conductance &
- High electro positivity
How does sodium acts as reducing agent. Write its reaction also.
Na is one of the electro positivity elements. It loses its valence electron easily and reduces another one.
Example: In NaCl, sodium atom (Na) going to lose electron and get oxidation, while Cl2 gains electron and get reduction as;
2Na + Cl2→2NaCl
I.E of alkaline earth metals is higher than alkali metals why?
Nuclear charge, atomic size, and valence electronic configuration are the factors which affect I.E.
Alkaline earth metals have smaller size and high nuclear charge, thus their valence electrons are tightly bonded to nucleus, thus need more and more energy to remove the valence electrons, that is why, I.E of alkaline earth metals is higher than alkali metals.
Na→Na++ e I.E=496Kj/mole.
Mg →Mg+++ e I.E=737.7 Kj/mole
Pure gold is not used for ornaments, why?
Pure gold is a noble metal. It is too much soft resist the stresses. Thus alloying gold with other metals like copper, silver, platinum (which increases it durability) is used for ornaments and jewelry.
What are the of magnesium?
Mg is used in:
- Manufacturing of alloys like duralumin (Al, Cu, Mg, Mu) and Magnalium (Al, Mg) which are used in construction of aircraft and cars.
- Photographic plate, firework etc.
- In extraction of Ti and U as deoxidant.
- MgSO4 is used in paper industry, soap and textile industry.
Write down reaction of Cl2 with NaOH with balance equations.
The expected reaction of Cl2 with NaOH is given below.
NaOH +Cl2 →NaOCl+HCl
How does ionization energies values very group?
Groupwise (top to bottom) I.E of elements decreases. This decrease is due to increase in atomic size and shielding effect.
| Element | I.E (KJ/mol) | Trend |
| Li | 520 |  Decreases |
| Na | 469 | |
| K | 419 | |
| Rb | 403 |
What happens during displacement reaction in halogens?
Generally the upper halogen, replaces lower halogen during displacement reaction as:
2NaBr+Cl2→2NaCl+Br2
2NaCl+F2→2NaF+ 2Cl2
