Question

Which of the following is correct statements? (1) Temporary hardness of water is due to the presence of bicarbonates of calcium and magnesium in it (2) Permutit is artificial zeolite (3) \(\mathrm{H}_{2} \mathrm{O}_{2}\) acts as an oxidizing agent in the following reaction: \(\mathrm{Cl}_{2}+\mathrm{H}_{2} \mathrm{O}_{2} \rightarrow \mathrm{O}_{2}+2 \mathrm{HCl}\) (4) \(\mathrm{H}_{2} \mathrm{O}_{2}\) is used an bleaching agent for delicate textiles. (a) \(1,2,3\) (b) \(2,3,4\) (c) \(1,2,4\) (d) \(1,3,4\)

Short answer

The correct statements are 1, 2, and 4. The answer is (c).

Step-by-step solution

Analyze Statement 1

Statement 1 claims that temporary hardness of water is due to the presence of bicarbonates of calcium and magnesium. This is correct. Temporary hardness is caused by the presence of soluble bicarbonates, which can be removed by boiling the water.

Analyze Statement 2

Statement 2 states that Permutit is artificial zeolite. This is correct. Permutit is indeed a synthetic form of zeolite used in water softening processes.

Analyze Statement 3

Statement 3 states that \( \mathrm{H}_{2} \mathrm{O}_{2} \) acts as an oxidizing agent in the reaction \( \mathrm{Cl}_{2} + \mathrm{H}_{2} \mathrm{O}_{2} \rightarrow \mathrm{O}_{2} + 2 \mathrm{HCl} \). In this reaction, \( \mathrm{H}_{2} \mathrm{O}_{2} \) is actually being reduced, and acts as a reducing agent, not an oxidizing agent.

Analyze Statement 4

Statement 4 suggests that \( \mathrm{H}_{2} \mathrm{O}_{2} \) is used as a bleaching agent for delicate textiles. This is true, as hydrogen peroxide is a gentle bleaching agent and is used for bleaching delicate fabrics.

Evaluate Answer Choices

Now, evaluate which options include the correct statements. Statements 1, 2, and 4 are correct. Hence, the correct answer choice from the given options is (c) 1,2,4.

Key concepts

Temporary Hardness

Temporary hardness in water is mainly due to the presence of dissolved bicarbonates of calcium and magnesium. These minerals dissolve into the water, making it hard. What makes this type of hardness 'temporary' is that it can be removed by simple processes like boiling. When water containing these bicarbonates is boiled, a chemical reaction occurs that precipitates out the calcium and magnesium as insoluble carbonates.
This reaction can be represented as:

• Calcium bicarbonate: \( ext{Ca(HCO}_3 ext{)}_2 ightarrow ext{CaCO}_3 ext{(solid)} + ext{CO}_2 ext{(gas)} + ext{H}_2 ext{O} \)
• Magnesium bicarbonate: \( ext{Mg(HCO}_3 ext{)}_2 ightarrow ext{MgCO}_3 ext{(solid)} + ext{CO}_2 ext{(gas)} + ext{H}_2 ext{O} \)

After boiling, the water is softer since the problematic minerals are removed. The precipitated carbonates form a scale, often seen in kettles and boilers, which explains why regular descaling may be needed in hard water areas.

Permutit

Permutit is a synthetic substitute for naturally occurring zeolites. Zeolites are microporous, aluminosilicate minerals used in water softening. Permutit works by exchanging its sodium ions (Na+) with calcium (Ca2+) and magnesium (Mg2+) ions present in hard water.
This ion-exchange process is what removes the hardness from water.

• When hard water passes through a column filled with permutit beads, the sodium ions swap places with the calcium and magnesium ions.
• This process effectively reduces the concentration of calcium and magnesium, softening the water.
• The main reaction can be outlined as: \( ext{Ca}^{2+} + 2 ext{Na-Permutit} ightarrow ext{Ca-Permutit} + 2 ext{Na}^+ \)

Over time, permutit loses its effectiveness as it becomes saturated with calcium and magnesium ions. The beads can be regenerated by flushing with a concentrated sodium chloride (salt) solution, swapping the calcium and magnesium ions back out.

Hydrogen Peroxide as Bleaching Agent

Hydrogen peroxide ( H ₂ O ₂) is widely known for its role in bleaching and disinfection. Its gentle bleaching properties make it ideal for delicate textiles.
This powerful yet delicate oxidizing agent reacts with stains and pigments by breaking them down, thereby removing color.

• Its chemical action as a bleaching agent relies on its ability to donate oxygen atoms, which oxidize and thereby remove unwanted substances.
• Hydrogen peroxide is often preferred over harsh bleaching agents like chlorine, as it is less likely to damage fibers, making it safe for use on delicate fabrics like silk and wool.
• In the context of reactions, it can serve as both an oxidizing and a reducing agent, depending on the reaction environment and conditions.

Aside from textiles, hydrogen peroxide is also used in various applications such as in paper bleaching and in the treatment of wounds due to its antiseptic properties. Its versatility is due to the reactive nature of the extra oxygen atom it contains.