Question

Select from the following a set of three metals which are found in free state :

• A. Al, Cu, Ag
• B. Au, Fe, Ag
• C. Cu, Au, Fe
• D. Ag, Au, Pt

Hint:

Metals at the bottom of the reactivity series are unreactive and often found in their "free" or "native" state. These include:
Gold (Au)
Silver (Ag)
Platinum (Pt)
Copper (Cu) can also be found in native form, though it's more reactive than Au, Ag, Pt. Look for sets containing these least reactive metals.

Answer 1

The Correct Option is D

Concept: Metals are found in the Earth's crust either in their native (free) state or in combined states as minerals (ores). The tendency to be found in a free state depends on their chemical reactivity. Less reactive metals are more likely to be found in their free state. Step 1: Understanding "Free State" "Free state" or "native state" means the metal exists in its elemental form, uncombined with other elements. This is characteristic of metals that are low in the reactivity series (also known as the activity series). Step 2: Reactivity of Metals
Highly Reactive Metals (e.g., K, Na, Ca, Mg, Al): Found only in combined states (ores).
Moderately Reactive Metals (e.g., Zn, Fe, Pb, Cu): Mostly found in combined states, but copper (Cu) can sometimes be found in its native state.
Least Reactive Metals (e.g., Ag, Au, Pt): These are often called "noble metals" due to their low reactivity. They are commonly found in their free state. Step 3: Analyzing the options Let's check the reactivity of the metals in each set:
(1) Al, Cu, Ag:
Aluminium (Al): Highly reactive, found as bauxite ore (\(Al_2O_3 \cdot xH_2O\)). Not in free state.
Copper (Cu): Moderately reactive, mostly as ores (e.g., chalcopyrite), but native copper exists.
Silver (Ag): Low reactivity, often found in free state. This set is not entirely free state metals due to Al.
(2) Au, Fe, Ag:
Gold (Au): Very low reactivity, found in free state.
Iron (Fe): Moderately reactive, found as ores (e.g., hematite, magnetite). Not typically in free state (except meteoritic iron).
Silver (Ag): Low reactivity, often found in free state. This set is not entirely free state metals due to Fe.
(3) Cu, Au, Fe:
Copper (Cu): Can be found in free state.
Gold (Au): Found in free state.
Iron (Fe): Not typically in free state. This set is not entirely free state metals due to Fe.
(4) Ag, Au, Pt:
Silver (Ag): Low reactivity, found in free state.
Gold (Au): Very low reactivity, found in free state.
Platinum (Pt): Very low reactivity, found in free state. All three metals in this set are known to be found in their free (native) state due to their low chemical reactivity. Therefore, the set Ag, Au, Pt consists of three metals commonly found in their free state.