Science (English Medium) कक्षा १२ - CBSE Question Bank Solutions for Chemistry

When acidified \[\ce{K2Cr2O7}\] solution is added to \[\ce{Sn^{2+}}\] salts then \[\ce{Sn^{2+}}\] changes to ______.

Highest oxidation state of manganese in fluoride is \[\ce{+4 (MnF4)}\] but highest oxidation state in oxides is \[\ce{+7 (Mn2O7)}\] because ______.

Although Zirconium belongs to 4d transition series and Hafnium to 5d transition series even then they show similar physical and chemical properties because ______.

Why is \[\ce{HCl}\] not used to make the medium acidic in oxidation reactions of \[\ce{KMnO4}\] in acidic medium?

Transition elements show magnetic moment due to spin and orbital motion of electrons. Which of the following metallic ions have almost same spin only magnetic moment?

(i) \[\ce{Co^{2+}}\]

(ii) \[\ce{Cr^{2+}}\]

(iii) \[\ce{Mn^{2+}}\]

(iv) \[\ce{Cr^{3+}}\]

Which of the following ions show higher spin only magnetic moment value?

(i) \[\ce{Ti^3+}\]

(ii) \[\ce{Mn2+}\]

(iii) \[\ce{Fe2+}\]

(iv) \[\ce{Co3+}\]

Transition elements form binary compounds with halogens. Which of the following elements will form \[\ce{MF3}\] type compounds?

(i) \[\ce{Cr}\]

(ii) \[\ce{Co}\]

(iii) \[\ce{Cu}\]

(iv) \[\ce{Ni}\]

Which of the following will not act as oxidising agents?

(i) \[\ce{CrO3}\]

(ii) \[\ce{MoO3}\]

(iii) \[\ce{WO3}\]

(iv) \[\ce{CrO^{2-}4}\]

Why does copper not replace hydrogen from acids?

Why E^Θ values for Mn, Ni and Zn are more negative than expected?

Why first ionisation enthalpy of Cr is lower than that of Zn?

Transition elements show high melting points. Why?

Out of \[\ce{Cu2Cl2}\] and \[\ce{CuCl2}\], which is more stable and why?

When a brown compound of manganese (A) is treated with \[\ce{HCl}\] it gives a gas (B). The gas taken in excess, reacts with \[\ce{NH3}\] to give an explosive compound (C). Identify compounds A, B and C.

Although fluorine is more electronegative than oxygen, but the ability of oxygen to stabilise higher oxidation states exceeds that of fluorine. Why?

Although \[\ce{Cr^3+}\] and \[\ce{Co^2+}\] ions have same number of unpaired electrons but the magnetic moment of \[\ce{Cr^3+}\] is 3.87 B.M. and that of \[\ce{Co^2+}\] is 4.87 B.M. Why?

Ionisation enthalpies of Ce, Pr and Nd are higher than Th, Pa and U. Why?

Explain why does colour of \[\ce{KMNO4}\] disappear when oxalic acid is added to its solution in acidic medium.

A solution of \[\ce{KMnO4}\] on reduction yields either a colourless solution or a brown precipitate or a green solution depending on pH of the solution. What different stages of the reduction do these represent and how are they carried out?

The second and third rows of transition elements resemble each other much more than they resemble the first row. Explain why?