How many coulombs of electricity would be needed to deposit 3.6 g of aluminium by the electrolysis of aluminium oxide dissolved in molten cryolite?

To deposit 3.6 g of aluminum, we first need to find the number of moles of aluminum.
Molar mass of Al = 27.0 g/mol.

$$\text{Moles of Al} = \frac{\text{Mass}}{\text{Molar mass}} = \frac{3.6 \text{ g}}{27.0 \text{ g/mol}} = 0.1333 \text{ mol}$$

The half-reaction for the deposition of aluminum from $\text{Al}^{3+}$ ions is:

$$\text{Al}^{3+} + 3e^- \to \text{Al}$$

From the stoichiometry, 1 mole of Al requires 3 moles of electrons.

$$\text{Moles of electrons} = 0.1333 \text{ mol Al} \times \frac{3 \text{ mol } e^-}{1 \text{ mol Al}} = 0.4 \text{ mol } e^-$$

Now, we use Faraday's constant (1F = 96500 C/mol) to find the total charge in coulombs.

$$\text{Charge (C)} = \text{Moles of electrons} \times \text{Faraday's constant}$$ $$\text{Charge (C)} = 0.4 \text{ mol } e^- \times 96500 \text{ C/mol } e^- = 38600 \text{ C}$$

The correct option is B.

$$\boxed{\text{B. 38600 C}}$$

Carbon black is an allotrope of carbon widely used as a reinforcing filler in rubber products, such as tires, to improve their strength, durability, and wear resistance.

The correct option is D.

$$\boxed{\text{D. Carbon black}}$$

The two rows of elements placed below the main body of the periodic table are the lanthanides (I) and actinides (II). Both of these series are also collectively known as f-block elements (III) because their distinguishing electrons occupy f-orbitals. Therefore, all three statements are correct.

The correct option is D.

$$\boxed{\text{D. I, II and III}}$$

The process of converting glucose to ethanol by the use of yeast is a biochemical process called fermentation. Yeast contains enzymes that catalyze this conversion.

The correct option is D.

$$\boxed{\text{D. fermentation}}$$

The loss of some or all of the water of crystallization when a hydrated compound is exposed to air is known as efflorescence.

• Hygroscopy is the ability of a substance to attract and hold water molecules from the surrounding environment.
• Dissociation is the process by which a compound breaks into smaller particles, typically ions, when dissolved in a solvent.
• Deliquescence is the process where a substance absorbs so much moisture from the air that it dissolves in the absorbed water to form a solution.

The correct option is D.

$$\boxed{\text{D. efflorescence}}$$

Electronegativity is a measure of the tendency of an atom in a molecule to attract shared electrons towards itself.

The correct option is A.

$$\boxed{\text{A. electronegativity}}$$

To find the molecular mass of $\text{CuSO}_4 \cdot 5\text{H}_2\text{O}$, we sum the atomic masses of all atoms present.
Given atomic masses: Cu = 63.5, S = 32.0, O = 16.0, H = 1.0.

$$\text{Molecular mass} = \text{Cu} + \text{S} + (4 \times \text{O}) + 5 \times (2 \times \text{H} + \text{O})$$ $$\text{Molecular mass} = 63.5 + 32.0 + (4 \times 16.0) + 5 \times (2 \times 1.0 + 16.0)$$ $$\text{Molecular mass} = 63.5 + 32.0 + 64.0 + 5 \times (2.0 + 16.0)$$ $$\text{Molecular mass} = 63.5 + 32.0 + 64.0 + 5 \times 18.0$$ $$\text{Molecular mass} = 63.5 + 32.0 + 64.0 + 90.0$$ $$\text{Molecular mass} = 249.5 \text{ g/mol}$$

The correct option is A.

$$\boxed{\text{A. 249.5 g}}$$

Pure substances are classified into two categories: elements and compounds. If a pure substance is not an element, it must be a compound. Mixtures are not pure substances.

The correct option is A.

$$\boxed{\text{A. compounds}}$$

When a neutron strikes an unstable nucleus and causes it to split into two or more smaller nuclei, along with the release of energy and more neutrons, this process is known as nuclear fission.

The correct option is A.

$$\boxed{\text{A. nuclear fission}}$$

Magnesium (Mg) has an atomic number of 12. Its electron configuration is $1s^2 2s^2 2p^6 3s^2$.
The valence electrons are the electrons in the outermost principal energy level. For magnesium, the outermost principal energy level is $n=3$, and the electrons are in the $3s$ orbital.

The correct option is D.

$$\boxed{\text{D. 3s orbital}}$$