Chemistry MCQs for NEET — Practice Questions with Answers

In the highest oxidation states, transition metals typically show acidic character due to the formation of high oxidation state oxides which are acidic in nature. For instance, Mn in +7 oxidation state forms $MnO_4^-$ which is acidic. Therefore, the statement 'In the highest oxidation states, the transition metals show basic.' is incorrect.

$Cr^{3+}$ is most stable in aqueous solution because it has a half-filled t2g configuration (3d^3) which provides extra stability due to exchange energy. This stability is greater compared to $V^{3+}$, $Ti^{3+}$, and $Mn^{3+}$ ions.

The maximum number of oxidation states is shown by elements with a partially filled d-subshell. In this case, $3d^5 4s^2$ (which corresponds to Manganese) has the most number of unpaired electrons and can exhibit multiple oxidation states ranging from +2 to +7. The half-filled $3d$ subshell provides stability across these states.

German silver is an alloy composed of Copper (Cu), Zinc (Zn), and Nickel (Ni). It is known for its silver-white appearance and is used in various applications such as cutlery and musical instruments.

To find the oxidation state of Cr in $K_2Cr_2O_7$, we can set up an equation based on the known oxidation states of K and O. Potassium (K) has an oxidation state of +1, and oxygen (O) has an oxidation state of -2. Let the oxidation state of Cr be x. The sum of the oxidation states in a neutral compound is zero.

For $K_2Cr_2O_7$:

$2(+1) + 2(x) + 7(-2) = 0$

$2 + 2x - 14 = 0$

$2x - 12 = 0$

$2x = 12$

$x = +6$

Therefore, the oxidation state of Cr in $K_2Cr_2O_7$ is +6.

Europium (Eu) is a lanthanide element that commonly exhibits +2 and +3 oxidation states. This is due to its electronic configuration, which allows it to achieve stability in both oxidation states.

All the given compounds $TiCl_3$, $FeCl_3$, and $CoCl_2$ are colored. This is because these compounds contain transition metals with unpaired electrons in their d-orbitals, which can absorb visible light and cause the compounds to appear colored.