Chemistry Test - 21

Assertion: Enzymes have active sites that hold substrate molecule for a chemical reaction. The substrate is held at the active site in a suitable and right position, for effective attack of reagent. This can be explained by lock and key model. The forces between the active site and substrate can be covalent bond, hydrogen bond, van der waal's forces etc.

Reason: Drugs compete with natural substrate by attaching covalently to the active site of enzyme. Many drugs acts as enzyme inhibitors. Inhibition by particular chemicals can be a source of insight into the mechanism of enzyme action: specific inhibitors can often be used to identify residues critical for catalysis.

Paramagnetism is common ins-block elements.

s-block element has a single electron in its valence shell. The single unpaired electron is responsible for the paramagnetism property.Paramagnetism is a form of magnetism where some materials are weekly attracted by an externally applied magnetic field.

Nickel (Ni) element forms interstitial compounds.

• It is known that a compound which is formed from a small atom whose radius is small enough that it sits in an interstitial "hole" in a metal lattice is known as an interstitial.
• When we move from left to right in a period then there occurs a decrease in size of the atoms. And, atoms with smaller size are able to sit in an interstitial hole.
• Out of the given options nickel is smaller in size. As a result it will be able to form an interstitial compound, whereas, Sc, Fe and Co are all larger in size than nickel. Therefore, they will not form interstitial compounds.

Among isomeric alkyl halides, the boiling point decreases with the increase in the alkyl group, because of branching the molecule attains spherical shape with less surface area \(\rightarrow\) intermolecular forces becomes weaker \(\rightarrow\) boiling point decreases.

\(\left(\mathrm{CH}_3\right)_3 \mathrm{CCl}<\left(\mathrm{CH}_3\right)_2 \mathrm{CHCH}_2 \mathrm{Cl}<\mathrm{CH}_3 \mathrm{CH}_2 \mathrm{CHClCH}_3<\mathrm{CH}_3 \mathrm{CH}_2 \mathrm{CH}_2 \mathrm{Cl}\)

Let V litre of 10 N HCl be mixed with (1 - V) litre of 4 N HCl to give (V + 1 - V) = 1 L of 7N HCl

As we know that,

\(N_{1} V_{1}+N_{2} V_{2}=N V\)

\(10 V+4(1-V)=7 \times 1\)

\(10 V+4-4 V=7\)

\(6 V=7-4\)

\(V=\frac{3}{6}=0.50 L\)

Volume of \(10 \mathrm{NHCl}=0.50 \mathrm{~L}\)

Volume of \(4 \mathrm{NHCl}=1-0.50=0.50 L\)

The current inside a copper voltameter is the same as the outside value. An electric current is a flow of electric charge. In electric circuits, this charge is often carried by moving electrons in a wire. It can also be carried by ions in an electrolyte, or by both ions and electrons such as in an ionised gas (plasma). Electric current is measured using a device called an ammeter.

VIA group or Group 16 elements belong to the oxygen family are also called chalcogens.

• The name is derived from the Greek word 'chalcos', which means 'ore' and 'gen', which means 'formation'.
• They are called so because most of the copper ores have copper in the form of oxides and sulphides.
• They also contain small amounts of selenium and tellurium.

The element forms amphoteric oxide 'is true regarding the typical element belonging to the 1st group of p-block elements'.

• The element forms amphoteric oxide. For example, \(Al\) forms \(\mathrm{Al}_{2} \mathrm{O}_{3}\) which is amphoteric.
• The typical element belonging to the 1st group of \(p\)-block elements is \(\mathrm{Al}\). The group is group 13 or group III-A.
• The element forms a sulphate of formula \(\mathrm{M}_{2}\left(\mathrm{SO}_{4}\right)_{3}\).
• Thus, \(Al\) forms \(\mathrm{Al}_{2}\left(\mathrm{SO}_{4}\right)_{3}\). The element does not show variable valency. It is a metal.

\(\mathrm{V}_2 \mathrm{O}_5, \mathrm{Cr}_2 \mathrm{O}_3\) is amphoteric oxide.

As we know that amphoteric oxides react with both acid as well as a base. So, from the above-given compounds, only vanadium pentoxide (\(\mathrm{V}_2 \mathrm{O}_5)\) and chromium oxide \((\mathrm{Cr}_2 \mathrm{O}_3)\) are amphoteric oxides.

This is so because vanadium pentoxide (\(\mathrm{V}_2 \mathrm{O}_5)\) can react with both acid and base. The vanadium pentoxide (\(\mathrm{V}_2 \mathrm{O}_5)\) reacts with base and acid to yield \(\mathrm{VO}_4^{-3}\) and \(\mathrm{VO}_4^{+}\)respectively.

Similarly, chromium oxide \((\mathrm{Cr}_2 \mathrm{O}_3)\) can also react with both acid and base.

It gives both acid as well as a base to give

\(\left[\mathrm{Cr}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{3+}\) and \(\left[\mathrm{Cr}(\mathrm{OH})_6\right]^{3-}\) respectively.

Manganese heptoxide \( \mathrm{Mn}_2 \mathrm{O}_7\) is an acid in which manganese has the oxidation state of \(+7\) it means that manganese tends to accept the pair of electrons that's why it cannot react with a base to give a pair of electrons and is considered Lewis acid.

Chromium oxide \(\mathrm{CrO}_2\), is present which is basic and because it has an oxidation state of \(+2\) and we know that the compound having a low oxidation state is basic.

In \(\mathrm{V}_2 \mathrm{O}_4\), the oxidation state of vanadium is \(+4\) which shows that it tends to donate a pair of the electron that's why it is as basic only and not amphoteric.