24. Give reason for the following:
[2]
a) Non metals in general, do not displace hydrogen from dilute acids.
b) Aluminium easily combines with oxygen but still it can be used for making
kitchen utensils.
25. Two circular coils A and B are placed closed to each other. If the current in the
coil A is changed , will some current be induced in the coil B? give reason . [2]
26. Mendel first crossed pure breed pea plants having round yellow seeds with pure
breed
pea plants having wrinkled green seeds and found that only round yellow
seeds were produced in the F1 generation. When F1 generation pea plants
having round yellow seeds were cross breed by self pollination then peas having
round yellow seeds and wrinkled green seeds were produced. Mendel collected
a total of 2224 seeds. What will be the number of
(i) Round yellow seeds (ii) Wrinkled green seeds?
[2]
Answers
Explanation:
a)
Metals are usually electron donors, that is, they are electropositive. Hydrogen is also an electron donor in Water molecule to Oxygen atom. Metals with more electropositivity can replace Hydrogen from water like Sodium. So such metals replace Hydrogen in dilute acids and form salts.
Example: 2 Na + 2 H CI ==> 2 Na Cl +
H2
Non metals can be electron acceptors or electron donors. If they are electron acceptors, then they are electronegative. They may replace Oxygen or Hydroxide or a Halogen. But they do not replace Hydrogen.
Many non-metals are below Hydrogen in the reactivity series. They are weaker than Hydrogen. So they do not displace Hydrogen from dilute acids. So nonmetals do not react with dilute acids.
b)
Even though aluminum can easily react with oxygen, it is used in making of kitchen utensil because when aluminum reacts with oxygen to form aluminum oxide. It forms a layer over surface of the surface of the metal.
4A1 + 302 → 2Al2O3
It will help to reduce the corrosion of aluminum metal. If any other metal used for making the utensils then it reacts with oxygen and forms their respective oxides. These oxides may cause harmfulness to us and change the chemical composition of utensils.
25)
When two circular coils A and B are placed close to each other, and the current in the coil A is changed then some current will be induced in the coil B and the magnetic field associated with it also changes. Thus the magnetic field around coil B also changes. This change in the magnetic field lines around coil B induces an electric current in it. This process is known as electromagnetic induction.
26)
In Fi generation only the dominant traits are expressed. All of them are same genotypically and phenotypically because all are formed from the same kind of gametes.. But as the offsprings are crossbred the recessive characteristics start showing up in the phenotype to give new combinations. Many new genotypic and phenotypic combinations are made due to different kinds of gametes available A punnets square can help in a better understanding of these new phenotypes. Hence we see yellow and round, yellow and wrinkled, green and round, green and wrinkled.