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Nickel acts as a catalyst in the hydrogenation of alkenes. Catalysts function by providing an alternative reaction pathway with a lower activation energy. By lowering the energy barrier, a larger fraction of reactant molecules have sufficient energy to react at a given temperature, which significantly increases the reaction rate. In this specific reaction, nickel adsorbs hydrogen onto its surface, weakening the H-H bonds and facilitating their addition to the alkene.

Aluminum is a highly reactive metal, placing it high on the reactivity series. Because it forms very stable oxides, it cannot be extracted from its ore (bauxite) using standard chemical reducing agents like carbon or coke. Instead, the industrial extraction process is by electrolysis of the purified ore.

Carbon(IV)oxide, commonly known as carbon dioxide (CO\(_2\)), is the primary gas used in fire extinguishers because it is non-combustible and denser than air. When released, it displaces the oxygen surrounding the fire, effectively "suffocating" the flames by removing one of the three essential components (fuel, heat, and oxygen) needed for combustion.

Sodium (Na\(^+\)) and potassium (K\(^+\)) are cations, meaning they have already lost an electron to achieve a stable noble gas configuration. Because they are positively charged, they have a tendency to accept electrons to return to their neutral elemental state (Na or K), a process called reduction. Conversely, option A, which is the tendency to give electrons describes the neutral atoms (Na and K) which are strong reducing agents that readily lose their single valence electron. Once they become Na\(^+\) and K\(^+\) ions, they have a stable octet and do not tend to lose further electrons. The correct answer is option C.

To determine the correct conditions, we use the Combined Gas Law, which relates the pressure, volume, and temperature of a fixed amount of gas: \(\frac{P\(_1\)V\(_1\)}{T\(_1\)}\) = \(\frac{P\(_2\)V\(_2\)}{T\(_2\)}\) Given: V\(_1\) = 400 cm\(^3\) , T\(_1\) = 400 K , P\(_1\) = 1 atm V\(_2\) = 200 cm\(^3\) , T\(_2\) = ? , P\(_2\) = ? We need to find which pair of pressure and temperature satisfies the equality P\(_1\)V\(_1\)/T\(_1\) = P\(_2\)V\(_2\)/T\(_2\) First, calculate the initial constant: \(\frac{1 atm . 400cm{^3}}{400K}\) = 1 Now, test Option C: P\(_2\) = 1 atm V\(_2\) = 200cm\(^3\) T\(_2\) = 200 K \(\frac{1 atm . 200cm{^3}}{200K}\) = 1 Options A, B and D will not give you 1.

The nucleus of an ordinary hydrogen atom (specifically the most abundant isotope, protium) consists of a single proton. Atomic Number: Hydrogen has an atomic number of 1, meaning it contains exactly one proton.

Acidified potassium dichromate (K\(_2\)Cr\(_2\)O\(_7\)) is a strong oxidizing agent that undergoes a distinct colour change during redox reactions. In an acidic medium, the chromium is present in the dichromate ion (Cr\(_2\)O\(_7\)\(^{2-}\)), where it has an oxidation state of +6. This ion gives the solution its characteristic orange colour. When it acts as an oxidizing agent, it accepts electrons and is reduced to chromium(III) ions (Cr\(^{3+}\)), where the oxidation state is +3. The formation of Cr\(^{3+}\) ions (often as chromium(III) sulfate in sulphuric acid solutions) turns the solution green.

While standard chemical definitions usually limit metalloids to a list of six elements (Boron, Silicon, Germanium, Arsenic, Antimony, and Tellurium), Selenium is frequently classified as a metalloid in various educational contexts and standardized tests because it exhibits intermediate properties between metals and nonmetals. Though more strictly defined as a nonmetal in some academic circles, it is the only viable answer among the choices provided that displays "metalloid-like" or semiconducting behavior.

Iodine can be separated from calcium chloride using sublimation because of the distinct physical properties of the two substances: 1. Iodine is a sublimable solid, meaning it transitions directly from a solid state to a gaseous state upon heating without passing through a liquid phase. 2. Calcium chloride is a non-sublimable ionic salt with a very high melting point, so it remains in the solid state while the iodine vapourizes.

Sodium chloride (common salt) is a versatile chemical used in various industrial and domestic processes. While it has many applications, it is not typically used for the primary treatment of water (such as purification or filtration of polluted water).

A metallic bond is an intramolecular (chemical) bond rather than an intermolecular force. It involves a lattice of metal cations surrounded by a "sea" of delocalized valence electrons. Because this bond exists within a substance to hold its atoms together rather than between discrete molecules, it does not qualify as an intermolecular force.

NO\(_2\) (nitrogen dioxide) is a covalent compound, not an ionic one. It is formed by the sharing of electrons between two non-metals: nitrogen and oxygen. Unlike ionic compounds, which typically involve the transfer of electrons from a metal to a non-metal, NO\(_2\) consists solely of non-metallic elements that form molecular bonds.

Sodium carbonate (Na\(_2\)CO\(_3\)) is an alkali metal carbonate that is extremely stable and does not decompose when heated strongly, even at Bunsen burner temperatures. This stability is due to the large size and low charge density of the sodium cation (Na\(^+\)), which has low polarizing power and cannot easily distort the carbonate ion (CO\(_3\)\(^{2-}\)) to break its carbon-oxygen bonds. Most group 1 carbonates (except lithium carbonate) exhibit this high thermal stability.

A universal indicator changes colour to represent the pH level of a substance. For instance, a red colour indicates a very low pH (typically 0 to 3), which corresponds to a strong or concentrated acid; for pH 0: Specifically produces a strong red or dark red colour, representing the highest acidity and for indicator Spectrum: the colour moves from red (strong acid) to orange/yellow (weak/dilute acid), green (neutral), and finally blue/purple (bases).

Nitrogen dioxide (NO\(_2\)) is unique because it undergoes a disproportionation reaction when dissolved in water. In this reaction, the nitrogen atom (which has an oxidation state of +4 in NO\(_2\) ) is both oxidized and reduced simultaneously, resulting in the formation of two distinct acids; 2NO\(_2\) + H\(_2\)O → HNO\(_2\) + HNO\(_3\)