Carbon dioxide is a pure substance, provided there is nothing else in it. A “pure substance” does not mean an element. Rather, it means that the given substance has definite physical and chemical properties. “Pure substances” can be either “Elements” or “Compounds” because all substances belonging to these categories have definite physical and chemical properties. A mixture does not have definite physical and chemical properties, and combine in varying proportions.

Correct Option: A

Carbon dioxide is a pure substance, provided there is nothing else in it. A “pure substance” does not mean an element. Rather, it means that the given substance has definite physical and chemical properties. “Pure substances” can be either “Elements” or “Compounds” because all substances belonging to these categories have definite physical and chemical properties. A mixture does not have definite physical and chemical properties, and combine in varying proportions.

Methyl orange is a pH indicator frequently used in titrations. It is often used in titrations because of its clear and distinct colour change. Because it changes colour at the pH of a mid-strength acid, it is usually used in titrations for acids. In a solution becoming less acidic, methyl orange moves from red to orange and finally to yellow with the reverse occurring for a solution increasing in acidity. The entire colour change occurs in acidic conditions. In an acid it is reddish and in alkali it is yellow.

Correct Option: D

Methyl orange is a pH indicator frequently used in titrations. It is often used in titrations because of its clear and distinct colour change. Because it changes colour at the pH of a mid-strength acid, it is usually used in titrations for acids. In a solution becoming less acidic, methyl orange moves from red to orange and finally to yellow with the reverse occurring for a solution increasing in acidity. The entire colour change occurs in acidic conditions. In an acid it is reddish and in alkali it is yellow.

Most of the human body is made up of water, H2O, with cells consisting of 65-90% water by weight. Therefore, it isn’t surprising that most of a human body’s mass is oxygen. Carbon, the basic unit for organic molecules, comes in second. 99% of the mass of the human body is made up of just six elements: oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus.

Correct Option: D

Most of the human body is made up of water, H2O, with cells consisting of 65-90% water by weight. Therefore, it isn’t surprising that most of a human body’s mass is oxygen. Carbon, the basic unit for organic molecules, comes in second. 99% of the mass of the human body is made up of just six elements: oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus.

In chemistry, an amphoteric species is a molecule or ion that can react as an acid as well as a base. Many metals (such as zinc, tin, lead, aluminium, and beryllium) and most metalloids form amphoteric oxides or hydroxides. Amphoterism depends on the oxidation state of the oxide. One type of amphoteric species areamphiprotic molecules, which can either donate or accept a proton (H+). Examples include amino acids and proteins, which have amine and carboxylic acid groups, and self-ionizable compounds such as water and ammonia.

Correct Option: C

In chemistry, an amphoteric species is a molecule or ion that can react as an acid as well as a base. Many metals (such as zinc, tin, lead, aluminium, and beryllium) and most metalloids form amphoteric oxides or hydroxides. Amphoterism depends on the oxidation state of the oxide. One type of amphoteric species areamphiprotic molecules, which can either donate or accept a proton (H+). Examples include amino acids and proteins, which have amine and carboxylic acid groups, and self-ionizable compounds such as water and ammonia.

A pearl is a hard object produced within the soft tissue (specifically the mantle) of a living shelled mollusk. Just like the shell of a clam, a pearl is made up of calcium carbonate in minute crystalline form, which has been deposited in concentric layers. The ideal pearl is perfectly round and smooth, but many other shapes of pearls (baroque pearls) occur. The finest quality natural pearls have been highly valued as gemstones and objects of beauty for many centuries, and because of this, the word pearl has become a metaphor for something very rare, fine, admirable, and valuable.

Correct Option: C

A pearl is a hard object produced within the soft tissue (specifically the mantle) of a living shelled mollusk. Just like the shell of a clam, a pearl is made up of calcium carbonate in minute crystalline form, which has been deposited in concentric layers. The ideal pearl is perfectly round and smooth, but many other shapes of pearls (baroque pearls) occur. The finest quality natural pearls have been highly valued as gemstones and objects of beauty for many centuries, and because of this, the word pearl has become a metaphor for something very rare, fine, admirable, and valuable.