Question

Which of the following are correct? 
i. V$^{2+}$ liberates hydrogen from a dilute acid
ii. The earlier members of lanthanide series behave more like aluminium 
iii. The ‘silver’ UK coins are made of CuNi alloy 
iv. The maximum oxidation state exhibited by Neptunium is +7

• A. i, iii only
• B. ii, iv only
• C. iii, iv only
• D. i, ii, iii only

Hint:

Oxidation States and Periodic Properties:

• Only some actinides exhibit high oxidation states like +6 and +7.
• Cu-Ni alloys are commonly used in coinage due to durability and corrosion resistance.
• Reducing ability is determined by electrode potentials.

Answer 1

The Correct Option is C

Let’s examine each statement: 
i. V$^{2}+$ liberates hydrogen from a dilute acid} — Incorrect 
V$^{2+}$ is not strong enough to reduce H$^+$ ions to H$_2$ gas. Only metals below hydrogen in the electrochemical series displace hydrogen; V$^{2+}$ does not fulfill this condition. 
ii. Earlier lanthanides behave more like aluminium — Incorrect 
Early lanthanides (like La, Ce) are not very similar to Al in terms of chemistry or oxidation states. Al is a p-block element with a +3 oxidation state, while lanthanides have f-electrons and show limited resemblance. 
iii. UK silver coins use Cu-Ni alloy — Correct 
Historically, British coins, especially after the discontinuation of actual silver, were made using cupronickel alloys (typically 75% Cu and 25% Ni). 
iv. Maximum oxidation state of Neptunium is +7 — Correct 
Neptunium (Np), an actinide, exhibits oxidation states ranging from +3 to +7. The +7 state is its maximum oxidation state, similar to other actinides like Pu and U. Thus, correct statements are iii and iv only.

Answer 2

Step 1: Analyze statement (i)
V$^{2+}$ ion does not liberate hydrogen from dilute acids because vanadium in the +2 oxidation state is not a strong enough reducing agent to displace hydrogen from acids.

Step 2: Analyze statement (ii)
The earlier members of the lanthanide series do not behave like aluminium. Aluminium is a p-block element with different chemical properties compared to the f-block lanthanides, which mainly show metallic behavior.

Step 3: Analyze statement (iii)
‘Silver’ UK coins are indeed made from a copper-nickel (CuNi) alloy, not pure silver, which gives them their silver-like appearance.

Step 4: Analyze statement (iv)
Neptunium (Np) can exhibit a maximum oxidation state of +7, which is one of the highest oxidation states known for actinide elements.

Step 5: Conclusion
Only statements (iii) and (iv) are correct.