Unit 8 – Chemical Reactivity (Short Questions)
Q.1 Why reactivity of metals increases down the group?
Q.2 Why reactivity of metals increases down the group?
Q.3 Why nitrogen forms compounds with alkaline earth metals directly?
Q.4 Why the second ionization energy of magnesium is higher than the first one?
Q.5 How oxygen reacts with group II A metals?
Q.6 What is relationship between electro positivity and ionization energy
Q.7 Why electro positivity decreases from left to right in a period?
Q.8 How electro positivity depends upon size and nuclear charge of an atom?
Q.9 Why ionization energies of alkaline earth metals are higher than alkali metals?
Q.10 Why silver and gold are least reactive?
Q.11 Can pure gold be used for making ornaments?
Q.12 Why copper is used for making electrical wires?
Q.13 What is the trend of variation in densities of alkali metals?
Q.14 Which metal is used for metal work?
Q.15 Why magnesium is harder than sodium?
Q.16 Why calcium is more electropositive than to magnesium?
Q.17 Why ionization energy of Na is less than Mg?
Q.18 Why the ionization energy of Na is more than K?
Q.1 Why reactivity of metals increases down the group?
Answer:
Reactivity of metals depends upon its tendency to lose electrons which is dependent upon the size of atoms. Thus reactivity of metals increases down the group because of increasing atomic size and decreasing ionization energy.
Q.2 Why reactivity of metals increases down the group?
Answer:
Physical properties of metals:
i. Almost all metals are solids (except mercury).
ii. They have high melting and boiling points.
iii. They possess metallic luster.
iv. They are malleable and ductile.
v. They are good conductors of heat and electricity.
vi. They have high densities.
Q.3 Why nitrogen forms compounds with alkaline earth metals directly?
Answer:
Nitrogen forms compounds with alkaline earth metals directly because alkaline earth metals from di-positive cations (M++). They have high charge density and polarization power. They can polarize nitrogen atoms easily and produce stable covalent nitrides with nitrogen.
3Mg +N2 → Mg3N2
Q.4 Why the second ionization energy of magnesium is higher than the first one?
Answer:
Second Ionization energy of magnesium is higher than the first one because after the removal of its electron nuclear charge increases and atomic size decreases. The remaining electrons will be attracted by the nucleus more strongly.
Q.5 How oxygen reacts with group II A metals?
Answer:
They are less reactive towards oxygen and they form oxides on heating.
2Mg + O2 —> 2MgO
Q.6 What is relationship between electro positivity and ionization energy
Answer:
Electropositivity depends upon the ionization energy which in turn depends upon size and nuclear charge of the atom. Small sized atoms with high nuclear charge have high ionization energy. Atoms having high ionization energy are less electropositive or metallic
Q.7 Why electro positivity decreases from left to right in a period?
Answer:
Electropositivity decreases across the period from left to right in the periodic table because. Size of atoms decreases due to increase in nuclear charges.
Q.8 How electro positivity depends upon size and nuclear charge of an atom?
Answer:
Electropositivity depends upon size and nuclear charge of an atom because when the size of atoms increases, electropositivity increases as it becomes easier to lose electrons. It also depends upon nuclear charge. If nuclear charge increases the electropositivity decreases because it becomes difficult to remove the electrons from outermost shell.
Q.9 Why ionization energies of alkaline earth metals are higher than alkali metals?
Answer:
Ionization energies of alkalme earth metals are higher than alkalimetals because the atomic size of alkalme earth metals one smaller and greater nuclear charge.
Q.10 Why silver and gold are least reactive?
Answer:
Silver and gold are least reactive because these metals do not lose their electrons easily.They do not have the tendency to make cations.
Q.11 Can pure gold be used for making ornaments?
Answer:
If not why? Ans: No, pure gold cannot be used for making ornaments because gold is too soft to be used as such. It is always alloyed with copper, silver or some other metal.
Q.12 Why copper is used for making electrical wires?
Answer:
Copper is used for making of electrical wires because it is a good conductor of electricity and can easily be drawn into wires.
Q.13 What is the trend of variation in densities of alkali metals?
Answer:
Densities of alkali metals increase down the group in the periodic table due to increase atomic mass.
Q.14 Which metal is used for metal work?
Answer:
Metal work means objects that are made in an artistic and skilful way. Copper metal is used in metal work because it is easily workable. It is used in many ornaments, plumbing, roafing and other operations.
Q.15 Why magnesium is harder than sodium?
Answer:
Magnesium is harder than sodium because in magnesium metallic bonding is stronger, than sodium. Magnesium involves 2 valence electrons in metallic bonding as compared to sodium which involves only one valence electron. Moreover magnesium has smaller atomic size and high ionization energy.
Q.16 Why calcium is more electropositive than to magnesium?
Answer:
Calcium is more electropositive than magnesium because calcium has larger size and greater nuclear charge than magnesium and in turn lower ionization energy than magnesium
Q.17 Why ionization energy of Na is less than Mg?
Answer:
Ionization energy of Na is less than Mg because Na has larger size and lower nuclear charge than Mg. It results in less nuclear attraction on valance electron in sodium.
Q.18 Why the ionization energy of Na is more than K?
Answer:
The ionization energy of sodium is more than K because down the group electropositive character increases and ionization energy decreases. It becomes easier for potassium to ose electrons than sodium