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Q: Is current a scalar or a vector quantity? Because it is equal to V/R. Both of them are scalars. But also it has both, direction and magnitude ?
Ans: (I) Electric current I = q/t. As both charge and time are scalars, therefore electric current is a scalar quantity.(II) We show electric current in a wire by an arrow to indicate the direction of flow of positive charge. But such arrows are not vectors because they do not obey the laws of vector algebra. This point can be explained y referring to fig. The wire OA and OB carry currents of 3A and 4A respectively. The total current in the wire CO is 3 + 4 = 7A irrespective of the angle between the wires OA and OB. This is not surprising because the charge is conserved so that magnitudes of current in wires OA and OB must add to give the magnitude of current in wire CO.

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(xv) Why the compounds of Sn+4 are covalent in nature while those of Sn+2 are ionic?
Ans; the valence electronic configuration of 4A group is ns2,np2. It means that these elements can show the oxidation state of 4 as well as 2.the top elements like C and Si always exist in +4 oxidation state while the bottom elements like Sn and Pb show +2 as well as +4 oxidation state.
As Sn+4 is small in size than Sn+2, and fajan,s rule state that small cation of high charge density has high polarizing tendency than larger cation of lower charge density. Therefore Sn+4 ion pull the electrons clouds more easily from the respective anion such that the electrons are effectively shared. That is why SnCl4 is covalent. Therefore SnCl4 is discrete molecule or molecular compound.
SnCl2 has more ionic character because of the higher size of Sn+2 ion. And exist in polymeric form.

why carboxylic acids are stronger acids than phenol, alcohol and water but weaker than mineral acids.
Ans: Carboxylic acids as well as carboxylate ion both are stabilized by resonance. However, carboxylate ion is more stabilized by resonance because its contributing structures are exactly identical. Carboxylic acids are stronger acids than phenols. It can be understood by comparing the hybrid structures of carboxylate ion and phenoxide ions. In carboxylate ion, the negative charge is equally distributed over two electronegative atoms (oxygen atoms) while in phenoxide ion, it is present only on one oxygen. Thus, carboxylate ion is more stabilized as compared to phenoxide ion. Hence, carboxylic acids ionize to the greater extent than phenols furnishing higher concentration of H+ ions. Therefore carboxylic acids behave as stronger acids than phenols.similar is the case with alcohol and water

Differentiate between alcohol and phenol?
Alcohol
1; when OH attached to aliphatic hydrocarbon, called alcohol.
2; examples are, CH3OH, CH3CH2OH
Alcohol have acidic properties but less than phenol.
alcohol does not react with NaOH and with FeCl3

Phenol
1;When OH attached to the aromatic carbon is called phenol.
C6H5OH.
phenol is more acidic than alcohol but less than carboxylic acid.
Phenol react with react with NaOH and with FeCl3.

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