In water treatment, the conversion of temporary hard water into soft water by boiling or by adding calculated amounts of calcium hydroxide is known by which process name?

Introduction / Context:
Hard water contains dissolved salts that interfere with soap lathering and can cause scale deposits in kettles and boilers. Water treatment methods are therefore used to convert hard water into soft water, especially when only temporary hardness is present. One classical method involves adding calcium hydroxide or boiling to remove bicarbonate hardness. This question asks for the specific name given to that method in standard water treatment terminology.

Given Data / Assumptions:

• The water contains temporary hardness, usually due to bicarbonates of calcium and magnesium.
• The method involves boiling or adding calcium hydroxide to remove this hardness.
• The process has a traditional name that appears in chemistry and environmental science textbooks.
• Several similar sounding options are provided, but only one is correct.

Concept / Approach:
Temporary hardness is primarily caused by dissolved bicarbonates of calcium and magnesium. When such water is boiled or treated with calcium hydroxide, the bicarbonates are converted into insoluble carbonates that precipitate out, thus softening the water. The classical method of adding calculated amounts of calcium hydroxide to remove bicarbonate hardness is known as Clarke's process. This name appears repeatedly in exam oriented teaching material and distinguishes it from other water softening methods such as ion exchange.

Step-by-Step Solution:
Step 1: Identify the type of hardness mentioned as temporary hardness, associated with bicarbonates. Step 2: Recall that boiling or adding calcium hydroxide converts these bicarbonates into insoluble carbonates. Step 3: Remember that the classical chemical method using calcium hydroxide to treat such water is called Clarke's process. Step 4: Examine the options and locate Clarke's process among the listed names. Step 5: Select Clarke's process as the correct name for this water softening technique.

Verification / Alternative check:
Standard chemistry references on environmental chemistry and water treatment describe various methods such as Clarkes process, lime soda process, and ion exchange. Among these, Clarkes process specifically refers to the treatment of temporary hard water with lime, which is calcium hydroxide. This method is designed to reduce bicarbonate hardness through precipitation. The close match between this description and the question confirms that Clarke's process is the correct answer and not the other invented names in the options.

Why Other Options Are Wrong:
Baker's process, Temp's process, and Lake's process are not standard names used in water treatment for removing temporary hardness. They appear to be distractors that sound similar to real process names but do not correspond to any widely recognised method in chemistry textbooks. Since these terms are not associated with the use of calcium hydroxide for softening temporary hard water, they cannot be correct in this context.

Common Pitfalls:
Students may be tempted to guess based on how familiar or scientific a name sounds, without recalling specific content from water treatment chapters. Another pitfall is confusion between different processes such as Clarkes process and the lime soda process, both of which use lime but in slightly different ways. To avoid mistakes, remember that Clarke's process is particularly linked with temporary hardness and the use of lime to precipitate bicarbonates. This clear association makes it easier to select the correct option in exams.

Final Answer:
The conversion of temporary hard water into soft water by boiling or adding calcium hydroxide is known as Clarke's process.