Which of the following is true regarding the physical science?
Which of the following is not correct ?
-
Solution
Lithium does not form peroxide.
Among the following components of cement which is present in highest amount?
-
Solution
Composition of cement depends upon its type.
Portland cement is most common kind and contains 51% tricalcium silicate, 24% of dicalcium silicate and 6% of tricalcium aluminate.
In crystals which one of the following ionic compounds would you expect maximum distance between centres of cations and anions?
-
Solution
As Cs+ ion has larger size than Li+ and I- has larger size than F-, therefore maximum distance between centres of cations and anions is in CsI.
Strongest bond is in between
-
Solution
According to Fajan rules, ionic character increases with increase in size of the cation and decrease in size of the anion.
Thus, CsF has higher ionic character than NaCl and hence bond in CsF is stronger than in NaCl.
Which compound will show the highest lattice energy ?
-
Solution
With the same anion, smaller the size of the cation, higher is the lattice energy.
The correct order of size of cations is –Na+ < K+ < Rb+ < Cs+
Hence, the lattice energy of NaF will be maximum.i.e., NaF.
Largest difference in radii is found in case of the pair
-
Solution
Radii of atoms increase as we go down the group due to the addition of extra energy shell.
Nuclear charge also increases on moving down the group but the influence of addition of energy shell predominates.
This predomination is larger in case when we move from Na to K among all the options given.
Which one of the following properties of alkali metals increases in magnitude as the atomic number rises ?
-
Solution
Within a group, ionic radius increases with increase in atomic number.
The melting points decrease down the group due to weakening of metallic bond.
The electronegativity and the 1st ionization energy also decreases down the group.
The pair whose both species are used in ant-acid medicinal preparations is :
-
Solution
NaHCO3 is used in medicine to neutralise the acidicty in the stomach.
Mg(OH)2 is basic in nature and dissolves in acids forming corresponding salts.
So both are used in antacid medicinal preparations.
Nitrolium is:
-
Solution
Nitrolim is CaCN2 + C.
It is used as fertilizer since it reacts with H2O to form NH3.
CaCN2 + 3H2O → CaCO3 + 2NH3.