Chemistry Test - 35

Urea was the first organic compound synthesized in a laboratory, which revolutionized and gave birth to organic chemistry.

German chemist Friedrich Wohler prepared urea in a laboratory in \(1828\) from ammonium cyanate. Nowadays urea is prepared commercially from liquid ammonia and liquid carbon.

If we assume that one-sixth the mass of an atom of \({ }^{12} C\) isotope is taken as the reference, the mass of one molecule of oxygen will be the same.

We know that:

\(12 \mathrm{~g} \text { of Carbon }=6.023 \times 10^{23} \text { atoms }\)

So, \(1 g=\frac{6.023 \times 10^{23}}{12} \)

\(\therefore 6 g \text { of carbon }=6 \times \frac{6.023 \times 10^{23}}{12} \)

\(=\frac{1}{2} \times 6.023 \times 10^{23}\)

This is our new Avogadro's number according to the given conditions.

Then, 1 atomic mass unit \(=\frac{1}{N_A}\)

\(=\frac{2}{6.023 \times 10^{23}}\)

Mass of 1 mole of \(O_2=32 \times\) Avogadro's number \(\times \frac{2}{6.023 \times 10^{23}}\)

\(=32 \times \frac{6.023 \times 10^{23}}{2} \times \frac{2}{6.023 \times 10^{23}} \)

\(=32 g\)

Therefore, there is no change in the mass number of \(\mathrm{O}_2\).

Heavy water (D₂O), also called deuterium oxide.

Heavy water is used as a moderator in some reactors because it slows down neutrons effectively and also has a low probability of absorption of neutrons.

We know,

\(E _{ cell }=\frac{0.059}{2} \log \frac{1}{ C }\)

where, \(C =100\) times

\(E _{\text {cell }}=-\frac{0.059}{2} \log \frac{1}{100}\) \((\because\log \frac{1}{100}=-2)\)

\(=-\frac{0.059}{2} \times -2\)

\(=0.059 V \)

\(=59~ mV\)

Thus, if the \(Zn ^{2+} / Zn\) electrode is diluted to \(100\) times than the emf is decreaseof \(59~ mV\).

Protein synthesis in a cell takes place in cytoplasm as well as in mitochondria. Protein synthesis takes place during the translation process inside the ribosomes. The ribosome is the protein factory of the cell. Ribosomes are found in both prokaryotic and eukaryotic cells. Ribosomes are also found in association with other cell organelles like mitochondria. The ribosomes are synthesized in the nucleolus. Also, the ribosomes are found attached to the Endoplasmic Reticulum (ER) means they are found freely present in the cytoplasm. \(70\) S ribosomes are found in the matrix of the mitochondria of both the prokaryotic and the eukaryotic cells. This is because mitochondria are the powerhouse of the cell and the major site for aerobic respiration and ATP production.

Au i.e Gold is the least reactive from the given elements.

Reactivity is defined as the rate at which a chemical substance tends to undergo a chemical reaction.

A catalyst works by providing an alternative reaction pathway to the reaction product. The rate of the reaction is increased as this alternative route has lower activation energy than the reaction route not mediated by the catalyst.

A person living in Shimla observed that cooking food without using pressure cooker takes more time. The reason for this observation is that at high altitude pressure decrease.

At high altitude, atmospheric pressure is low. Therefore, liquids at high altitude boil at lower temperatures in comparison to that at sea level hence pressure cooker is used for cooking food which otherwise takes more time.

Dissociation of sulfuric acid,

\(\mathrm{H}_{2} \mathrm{SO}_{4} \rightarrow 2 \mathrm{H}^{+}(\mathrm{aq})+\mathrm{SO}_{4}^{-2}(\mathrm{aq})\)

Disssociation of water,

\(\mathrm{H}_{2} \mathrm{O} \rightarrow \mathrm{H}^{+}(\mathrm{aq})+\mathrm{OH}^{-}(\mathrm{aq})\)

At Anode: \(4 \mathrm{OH}^{-} \rightarrow 2 \mathrm{H}_{2} \mathrm{O}^{+}(l)+\mathrm{O}_{2}(\mathrm{~g})+4 \mathrm{e}^{-}\)

Thus, on electrolysis of dilute sulphuric acid using Platinum (Pt) electrode, the product obtained at anode will beOxygen gas.

The monohalogen derivatives of alkanes are calledHaloalkanes.

So, on a general basis saturated hydrocarbon is called alkanes,Generally, when one hydrogen atom of an alkane is replaced by a halogen atom, then the compound obtained is called a mono halogen derivative of alkanes. Typically they are called as alkyl halides (depending on the degree of substitution at the carbon atom carrying the halogen, alkyl halides are classified into primary, secondary and tertiary alkyl halides) or halo alkenes.

The general formula is \(C_{n} H_{2 n+1} X\)