Chemistry Test-18

According to Raoult's law, for dilute solutions containing non-volatile solute, the relative lowering of vapour pressure,

\(\Delta \mathrm{P} / \mathrm{P}^{\circ}\) is equal to the mole fraction of solute, \(\mathrm{X}_2\). It is a colligative property.

Here, the silver electrode acts as a cathode, whereas the copper electrode serves as the anode. This is because the standard electrode potential of the silver electrode is greater than that of the copper electrode. The standard electrode potential of the cell can now be calculated, as shown below.

\(E _{\text {cell }}^0= E _{\text {cathode }}^0- E _{\text {anode }}^O=0.8 V -0.34 V =0.46 V\)

Since the charge on the copper ion is \(+2\) and the charge on the silver ion is \(+1\), the balanced cell reaction is:

\(2 Ag ^{+}+ Cu \rightarrow 2 Ag + Cu ^{2+}\)

Since two electrons are transferred in the cell reaction, \(n=2\). The Nernst equation for this electrochemical cell can be written as follows.

\(E _{\text {cell }}= E _{\text {cell }}^0-(\frac{0.0592}{2}) \times \log \left(\frac{0.1}{\left[ Ag ^{+}\right]^2}\right)\)

\(0.422 V =0.46-0.0296 \times\left(-1-2 \log \left[ Ag ^{+}\right]\right)\)

Therefore, \(-2 \log \left[ Ag ^{+}\right]=1.283+1=2.283\)

Or, \(\log \left[ Ag ^{+}\right]=-1.141\)

\(\left[ Ag ^{+}\right]=\)antilog \((-1.141)=0.0722 M\)

To find electrode potential, electrochemical series is used.

The alkaline earth metals are weaker reducing agents than alkali metals. And like alkali metals, the reducing character of the alkaline earth metals increases down the group.

So, the decreasing order of standard electrode potential will be:

\(Mg > Ca > Ba > K\)

Mists are the vapours in the air that undergo condensation. Their production is also possible by liquid sprays. For example: Herbicides and pesticides are used in the form of sprays in agriculture but sometimes it misses its target and enters the atmosphere thereby forming mists. Mists are a non-viable particulate matter which is classified on the basis of size and nature.

So, both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.

The oxidation of oils or fats in a food isknown as rancidity.

When fats and oils are oxidised, they become rancid and their smelland taste change. This phenomenon is called rancidity.Usually substances which prevent oxidation(antioxidants) are added to foods containing fats and oil. Theyare often used as preservatives in fat-containing foods to delay the onset or slow the development of rancidity due to oxidation.An example of rancidity is when a chips pack is exposed to atmospheric air which results in a change in taste and odour.

Autoxidation is any oxidation that occurs in presence of oxygen. The term is usually used to describe the degradation of organic compounds in air (as a source of oxygen). Autoxidation produces hydroperoxides i.e. formation of H₂O by the oxidation of H₂O₂,and cyclic organic peroxides. These species can react further to form many products. The process is relevant to many phenomena including aging, paint, and spoilage of foods, degradation of petrochemicals, and the industrial production of chemicals. Autoxidation is important because it is a useful reaction for converting compounds to oxygenated derivatives, and also because it occurs in situations where it is not desired (as in the destructive cracking of the rubber in automobile tires or in rancidification).

Ductility is a physical property of matter, usually metals. It is the ability of metals to be drawn into thin wires. Non-metals are non-ductile in nature.

Out of the given elements platinum, aluminium and copper are metals while carbon is a non-metal. Therefore, carbon cannot be drawn into a wire.

When the quantity of acids in the raining water is more than the average, then such rain is called 'Acid rain'.

We are aware that normally rainwater has a pH of 5.6.When thepH of the rainwater drops below 5.6, it is called acid rain.

Acid rain refers to the ways in which acid from the atmosphere is deposited on the earth’s surface.Oxides of nitrogenand sulphurwhich areacidic in naturecan be blown by the wind along with solid particles in the atmosphere and finally settle down either on the ground asdry depositionor in water, fog and snow aswet deposition.

∴ The average pH value of acid rain is 4 to 5 and hence the average value of 4.5.

The bad effects of acid rain

• When acid rain falls and flows as groundwater reaches rivers, lakes, etc, it affects plants and animal life in the aquatic ecosystem.
• Acid rain isharmful to agriculture, trees, and plants as it dissolves and washes away nutrients needed for their growth.
• It causes respiratory ailments in human beings and animals.
• It may also causecorrosionin many buildings bridges, monuments, fencing, etc.
• It causes irritation in the eyes and skin of human beings.
• This rain reduces the lustreof the metals too.
• Acid rain damages buildings and other structures made of stone or metal.
• The Taj Mahal in India has been affected by acid rain.

Internal energy is due to motion of particles in a system. As internal energy depends on temperature. As we know temperature in isothermal process is constant so the internal energy will also be constant thus the change in internal energy will be zero.

Ureaseenzyme was first isolated and purified in the form of crystals.