The colour of transition-metal compounds is normally associated with d-d transitions. However, some transition metal compounds show intense colour in solution in spite of absence of d-electrons. For example, the orange colour of TiBr4, yellow colour of CrO42– , orange colour of Cr2O2–7, intense red colour of [Fe(SCN)₄] and deep purple of MnO₄ are not due to d—d transitions. In the case of MnO₄ ion, the color is due to charge transfer and not due to d-d transitions.

Correct Option: C

The colour of transition-metal compounds is normally associated with d-d transitions. However, some transition metal compounds show intense colour in solution in spite of absence of d-electrons. For example, the orange colour of TiBr4, yellow colour of CrO42– , orange colour of Cr2O2–7, intense red colour of [Fe(SCN)₄] and deep purple of MnO₄ are not due to d—d transitions. In the case of MnO₄ ion, the color is due to charge transfer and not due to d-d transitions.

The most abundant metal on Earth is aluminum. Aluminum is the third most abundant element in the Earth’s crust, and makes up 8 percent of it by parts per million. The most abundant element in the Earth’s crust is Oxygen followed by Silicon. Both of these are non-metals.

Correct Option: C

The most abundant metal on Earth is aluminum. Aluminum is the third most abundant element in the Earth’s crust, and makes up 8 percent of it by parts per million. The most abundant element in the Earth’s crust is Oxygen followed by Silicon. Both of these are non-metals.

Firewood, agricultural waste (straw, etc.) and animals waste (cowdung) are the important components of non-commercial energy. It is generally used in the rural area for domestic purposes— mainly cooking. Coal, petroleum products, natural gas and, electricity are the important components of commercial energy.

Correct Option: D

Firewood, agricultural waste (straw, etc.) and animals waste (cowdung) are the important components of non-commercial energy. It is generally used in the rural area for domestic purposes— mainly cooking. Coal, petroleum products, natural gas and, electricity are the important components of commercial energy.

Anthracite is the highest rank of coal. It is the most metamorphosed type of coal, in which the carbon content is between 92.1% and 98%. Anthracite coal generally has the highest heating value per ton on a mineral-matter-free basis. Anthracite is often referred to as hard coal.

Correct Option: A

Anthracite is the highest rank of coal. It is the most metamorphosed type of coal, in which the carbon content is between 92.1% and 98%. Anthracite coal generally has the highest heating value per ton on a mineral-matter-free basis. Anthracite is often referred to as hard coal.

Atomic number of a chemical element is the number of protons found in the nucleus of an atom of that element, and therefore identical to the charge number of the nucleus. It determines the place of an element in the periodic table. In an uncharged atom, the atomic number is also equal to the number of electrons.

Correct Option: B

Atomic number of a chemical element is the number of protons found in the nucleus of an atom of that element, and therefore identical to the charge number of the nucleus. It determines the place of an element in the periodic table. In an uncharged atom, the atomic number is also equal to the number of electrons.