Calgon is used for water treatment. Which of the following statement is $NOT$ true about Calgon?
- Calgon contains the $2^{\text {nd }}$ most abundant element by weight in the Earth's crust.
- It is polymeric compound and is water soluble.
- It is also known as Graham's salt
- It does not remove $Ca ^{2+}$ ion by precipitation.
The Correct Option is A
Solution and Explanation
To solve the question, we need to determine which statement about Calgon is \(NOT\) true based on its characteristics and composition.
Calgon, commonly used in water treatment, is primarily composed of sodium hexametaphosphate (\(\text{Na}_6\text{P}_6\text{O}_{18}\)). It's important to analyze each given statement:
- Calgon contains the \(2^{\text{nd}}\) most abundant element by weight in the Earth's crust.
- The second most abundant element in the Earth's crust is Silicon (Si), whereas Calgon primarily contains phosphorus, oxygen, and sodium.
- This statement is incorrect as Silicon is not a component of Calgon.
- It is a polymeric compound and is water soluble.
- Calgon is indeed a polymeric compound and it easily dissolves in water, which aids in water treatment by preventing the formation of scale.
- This statement is correct.
- It is also known as Graham's salt.
- The name "Graham's salt" often refers to sodium hexametaphosphate, another name for Calgon.
- This statement is correct.
- It does not remove \(Ca^{2+}\) ion by precipitation.
- Calgon sequesters calcium ions, preventing them from precipitating as scale. It operates by complexing with calcium ions, rather than by precipitation.
- This statement is correct.
By analyzing each statement, we can conclude that the statement "Calgon contains the \(2^{\text{nd}}\) most abundant element by weight in the Earth's crust" is \(NOT\) true.
Thus, the correct answer is the first option: "
Calgon contains the \(2^{\text{nd}}\) most abundant element by weight in the Earth's crust.".
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Concepts Used:
Hydrogen Bonding
Hydrogen bonding implies the formation of hydrogen bonds which are an attractive intermolecular force. An example of hydrogen bonding is the bond between the H atom and the O atom in water.
A special type of intermolecular attractive force arises only in the compounds having Hydrogen atoms bonded to an electronegative atom. This force is known as the Hydrogen bond. For instance, in water molecules, the hydrogen atom is bonded to a highly electronegative Oxygen.
The conditions for hydrogen bonding are:
- The molecule must contain a strongly electronegative atom that is bound to the hydrogen atom. The higher the electronegativity, the more polarized is the molecule.
- The electronegative atom must be small. The smaller the size, the greater the electrostatic magnetism.
Effects of Hydrogen Bonding on Elements:
Association: The molecules of carboxylic acids exist as dimer because of the hydrogen bonding. The molecular masses of such compounds are found to be double than those calculated from their simple formula.
Dissociation: In aqueous solution, HF dissociates and gives the difluoride ion instead of fluoride ion. This is due to hydrogen bonding in HF. The molecules of HCl, HBr, HI do not form a hydrogen bond. This explains the non-existence of compounds like KHCl2, KHBr2, KHI2.
Types of Hydrogen bonding
- Intramolecular Hydrogen bonding: When hydrogen bonding takes place between different molecules of the same or different compounds, it is called intermolecular hydrogen bonding.
- Intermolecular hydrogen bonding: The hydrogen bonding which takes place within a molecule itself is called intramolecular hydrogen bonding.
- Symmetrical Hydrogen bonding: The symmetric hydrogen bond is a type of a three-centre four-electron bond.