April 2024 - Page 6 of 7 - Digital Discite

Aluminum reacts slowly with dil. H₂SO₄ to produce:

A. Nitrogen gas
B. Oxygen gas
C. Hydrogen gas
D. Sulphur dioxide gas

Answer

C. Hydrogen gas

When aluminum reacts with dilute sulfuric acid (H₂SO₄), it undergoes a single displacement reaction. Here’s the balanced chemical equation for this reaction:

2Al(s) + 3H₂SO₄(aq) → 3H₂(g) + Al₂(SO₄)₃(aq)

As you can see, the reaction produces hydrogen gas (H₂) and aluminum sulfate (Al₂(SO₄)₃).

Aluminum reacts slowly with dil. H₂SO₄ to produce: Read More »

Electrical conductivity of alkaline earth metals _____ from Be to Ra.

A. Remains disturbed
B. Remains same
C. Increases
D. Decreases

Answer

C. Increases

The electrical conductivity of alkaline earth metals increases from Be to Ra.

Here’s why:

As we move down the group (Be to Ra) in the periodic table for alkaline earth metals:

Atomic size increases: The outer electrons are further away from the nucleus, experiencing a weaker attractive force. This makes them more readily available for conduction.
Number of valence electrons remains the same (2): All alkaline earth metals have two valence electrons in their outermost shell, which they can contribute to conduction.

The combined effect of increasing atomic size and readily available valence electrons leads to improved electrical conductivity down the group from Be to Ra.

Electrical conductivity of alkaline earth metals _____ from Be to Ra. Read More »

Hydrogen, an ordinary temperature and pressure exist in nature in the:

A. Solid state
B. Liquid state
C. Gaseous state
D. Plasma state

Answer

C. Gaseous state

At ordinary temperature (around room temperature) and pressure, hydrogen exists as a gas. It’s the lightest element and due to its weak intermolecular forces, it readily fills the available volume as a gas.

Solid hydrogen: Requires extremely low temperatures (below -259°C) to solidify.
Liquid hydrogen: Achieved at very low temperatures (around -253°C) and remains a liquid even at room temperature if kept in a well-insulated container.
Plasma state: Requires very high temperatures and is not the typical state for hydrogen under normal conditions.

Hydrogen, an ordinary temperature and pressure exist in nature in the: Read More »

Coinage metals are elements of sub-group I-B and these includes:

A. Cu, Ag, Au
B. Zn, Cd, Hg
C. Fe, Co, Ni
D. Cu, Zn, Ni

Answer

A. Cu, Ag, Au

Coinage metals are elements of subgroup I-B and these include:

Copper (Cu)
Silver (Ag)
Gold (Au)

Subgroup I-B, also known as group 11, is located on the left side of the p-block in the periodic table. These elements are known for their excellent electrical conductivity, malleability, and ductility. Their unique properties make them ideal for use in various applications, including:

Electrical wiring: Copper is widely used in electrical wires due to its high conductivity.
Jewelry: Silver and gold are popular choices for jewelry because of their lustrous appearance and ability to be shaped into intricate designs.
Electronics: Gold is used in electronic components due to its resistance to corrosion.
Coins: Historically, copper, silver, and gold were the primary metals used to mint coins. Although less common today, some collector’s coins and high-value currencies may still incorporate these metals.

Coinage metals are elements of sub-group I-B and these includes: Read More »

Reaction rate is expressed in units of:

A. mole dm^-3S^-1
B. mole dm^-3
C. mole dm^-3N^-1
D. dm^-1S^-1

Answer

A. mole dm^-3S^-1

The reaction rate expresses the change in concentration of a reactant or product per unit time.

Here’s a breakdown of the units involved:

mole: This represents the amount of a substance in terms of moles.
dm³ (cubic decimeter): This represents the volume of the solution, often used interchangeably with liters (L).
s⁻¹ (per second): This represents the time unit, indicating the rate of change per second.

Reaction rate is expressed in units of: Read More »

Le-Chateller’s principle is a generalization which enables us to produce the effect of change of:

A. Pressure only
B. Pressure, temperature & concentration
C. Temperature & concentration
D. Only temperature

Answer

B. Pressure, temperature & concentration

Le-Chatlier’s principle is a fundamental concept in chemical equilibrium. It states that if a stress is applied to a system at equilibrium, the position of the equilibrium will shift in a way that tends to counteract the applied stress and re-establish equilibrium. This principle allows us to predict how a chemical equilibrium will respond to changes in various factors:

Pressure: If pressure is increased, the equilibrium will shift towards the side with fewer gas molecules to reduce the overall pressure. Conversely, decreasing pressure will favor the side with more gas molecules.
Temperature: The effect of temperature depends on whether the reaction is exothermic (releases heat) or endothermic (absorbs heat). Increasing temperature favors the endothermic reaction (to consume the added heat), while decreasing temperature favors the exothermic reaction (to release heat).
Concentration: If the concentration of a reactant is increased, the equilibrium will shift to consume the added reactant, favoring the product side. Conversely, decreasing the concentration of a reactant will favor the reactant side. Similarly, changes in product concentration will also affect the equilibrium position in the opposite direction.

Therefore, Le-Chatlier’s principle helps us predict the effect of changes in pressure, temperature, and concentration on a chemical equilibrium.

Le-Chateller’s principle is a generalization which enables us to produce the effect of change of: Read More »

Any property which depends upon the state of system is called:

A. Enthalpy
B. State function
C. Free energy
D. Internal energy

Answer

B. State function

State function: A property of a system whose value depends only on the current state of the system (e.g., temperature, pressure, volume) and not on the path taken to reach that state. This is the most general term encompassing all the other options.
Enthalpy (H): A state function representing the total energy of a system, including its internal energy and the energy of pressure-volume work.
Internal energy (U): A state function representing the total kinetic and potential energy of the particles within a system.
Free energy (G): A state function that determines the spontaneity of a process at constant temperature and pressure. It considers both the enthalpy change and the entropy change of the system.

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Unequal sharing of electron pair results in:

A. Ionic bond
B. Polar covalent bond
C. Hydrogen bond
D. All of the above

Answer

B. Polar covalent bond

Ionic bonds involve a complete transfer of electrons from one atom to another.
Hydrogen bonds are a specific type of dipole-dipole attraction between a hydrogen atom bonded to a highly electronegative atom (O, N, F) and another electronegative atom.
Polar covalent bonds arise due to the unequal sharing of electrons between atoms with different electronegativities.

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