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Chemistry MCQs | Objective Type Questions | MCQs SET-5
1.Which metal has the highest melting point among all metals?
Correct Answer: A [Tungsten]
Notes:
Of all the metals, Tungsten has the highest melting point (3422 °C). Also, it has the lowest vapor pressure and the highest tensile strength among all the metals.
Of all the metals, Tungsten has the highest melting point (3422 °C). Also, it has the lowest vapor pressure and the highest tensile strength among all the metals.
2.Which of the following is also known as Carbolic Acid?
Correct Answer: B [Phenol]
Notes:
Because of their high acidity, phenols are often called carbolic acids. Phenol is an aromatic organic compound with the molecular formula C₆H₅OH.
Because of their high acidity, phenols are often called carbolic acids. Phenol is an aromatic organic compound with the molecular formula C₆H₅OH.
3.Who gave law of conservation of mass?
Correct Answer: C [Lavoisier]
Notes:
Antoine Lavoisier (1743 – 1794) was a French chemist who is sometimes referred to as the “father of modern chemistry”. He developed the “law of conservation of mass” which states that for any closed system, the mass of the system must remain constant over time. He also proved that sulfur was an element and named the elements oxygen and hydrogen.
Antoine Lavoisier (1743 – 1794) was a French chemist who is sometimes referred to as the “father of modern chemistry”. He developed the “law of conservation of mass” which states that for any closed system, the mass of the system must remain constant over time. He also proved that sulfur was an element and named the elements oxygen and hydrogen.
4.Washing soda can be obtained from baking soda by __:
Correct Answer: A [Heating]
Notes:
Baking soda decomposes into sodium carbonate upon heating.
Baking soda decomposes into sodium carbonate upon heating.
5.Which of the following salts has no water of crystallization?
Correct Answer: D [Baking Soda]
Notes:
Baking soda is chemically sodium bicarbonate (NaHCO3) which does not contain any water of crystallization.
Baking soda is chemically sodium bicarbonate (NaHCO3) which does not contain any water of crystallization.
6.“Petroleum” can be categorised under which one of the following terms?
Correct Answer: B [Hydrocarbons ]
Notes:
Petroleum, a complex mixture of hydrocarbons that occur in Earth in liquid, gaseous, or solid form. The term is often restricted to the liquid form, commonly called crude oil, but, as a technical term, petroleum also includes natural gas and the viscous or solid form known as bitumen, which is found in tar sands. The liquid and gaseous phases of petroleum constitute the most important of the primary fossil fuels. Liquid and gaseous hydrocarbons are so intimately associated in nature that it has become customary to shorten the expression “petroleum and natural gas” to “petroleum” when referring to both.
Petroleum, a complex mixture of hydrocarbons that occur in Earth in liquid, gaseous, or solid form. The term is often restricted to the liquid form, commonly called crude oil, but, as a technical term, petroleum also includes natural gas and the viscous or solid form known as bitumen, which is found in tar sands. The liquid and gaseous phases of petroleum constitute the most important of the primary fossil fuels. Liquid and gaseous hydrocarbons are so intimately associated in nature that it has become customary to shorten the expression “petroleum and natural gas” to “petroleum” when referring to both.
7.Which of the following causes the rusting of iron?
- Oxidation
- Reduction
- Chemical reaction with oxygen
- Chemical reaction with CO2
Select the correct answer from the codes given below:
Correct Answer: D [Only 1 and 3]
Notes:
Rust is composed of iron oxides. In colloquial usage, the term is applied to red oxides, formed by the reaction of iron and oxygen in the presence of water or air moisture. When impure (cast) iron is in contact with water, oxygen, or other strong oxidants, or acids, it rusts. If salt is present, for example in seawater or salt spray, the iron tends to rust more quickly, as a result of electrochemical reactions. Supporting the process of rusting.
Rust is composed of iron oxides. In colloquial usage, the term is applied to red oxides, formed by the reaction of iron and oxygen in the presence of water or air moisture. When impure (cast) iron is in contact with water, oxygen, or other strong oxidants, or acids, it rusts. If salt is present, for example in seawater or salt spray, the iron tends to rust more quickly, as a result of electrochemical reactions. Supporting the process of rusting.
8.When a metal is heated in a flame, the electrons absorb energy and jump to higher energy state. On coming back to the lower energy siate, they emit light, which we can observe in:
Correct Answer: C [Emission spectra]
Notes:
When a metal atom is strongly heated, its electrons absorb the heat energy and jump to a higher energy level. When the electron returns to its original position, it gives off the energy it had absorbed in the form of light. The result of all these jumps is to produce what is called an emission spectrum. It appears as a set of coloured lines that correspond to the energy the electron released at each stage of its fall back to its original state.
When a metal atom is strongly heated, its electrons absorb the heat energy and jump to a higher energy level. When the electron returns to its original position, it gives off the energy it had absorbed in the form of light. The result of all these jumps is to produce what is called an emission spectrum. It appears as a set of coloured lines that correspond to the energy the electron released at each stage of its fall back to its original state.
9.Which one of the following has a maximum tendency to form M3 ion?
Correct Answer: A [N]
Notes:
Thee general electronic configuration of group 15 elements (N, P, As, Sb and Bi) is ns2np3. Since Nitrogen has smallest size and greatest electronegativity in the family, it may gain three electrons and attain noble gas configuration, forming nitride N3- ions. The other members show little tendency to form tri-negative M3- ions. Their electronegativity is so low that they would generally form covalent compounds even with highly electropositive elements.
Thee general electronic configuration of group 15 elements (N, P, As, Sb and Bi) is ns2np3. Since Nitrogen has smallest size and greatest electronegativity in the family, it may gain three electrons and attain noble gas configuration, forming nitride N3- ions. The other members show little tendency to form tri-negative M3- ions. Their electronegativity is so low that they would generally form covalent compounds even with highly electropositive elements.
10.In a periodic table, while moving from left to right in a period, number of remains same of:
Correct Answer: C [shells]
Notes:
The periodic properties of an element depend on valency and number of shells in an atom. As we move down a group the number of shell increases successively such that the number of the shell of an element is equal to the number of periods to which it belongs. As we move across a period, the number of shell remains the same. For example, elements of the second period have two shells.
The periodic properties of an element depend on valency and number of shells in an atom. As we move down a group the number of shell increases successively such that the number of the shell of an element is equal to the number of periods to which it belongs. As we move across a period, the number of shell remains the same. For example, elements of the second period have two shells.
