CBSE Questions for Class 11 Engineering Chemistry Some P-Block Elements Quiz 9 - MCQExams.com

Since X is non-reactive and it cannot be attacked by the halogens, hydrogen, and acids as well as metals. Even at high-temperature reaction is not happening. But exceptionally it reacts with HF and NaOH. Thus, X will be $$SiO_{2}$$.

It doesn't react because of the difficulty of breaking up its giant covalent structure. It is insoluble in the water and organic solvents.

The correct option is A.

• Topaz is a rare silicate mineral with a chemical composition of $$Al_2SiO_4(FOH)_2$$. It usually forms in fractures and cavities of igneous rocks such as pegmatite and rhyolite, late in their cooling history. 
  
• Opal is a non-crystalline form of the mineral silica and is formed from amorphous "balls" or "lumps" of silica. So the opal is a very unique gem compared with others, like diamonds or a ruby which is formed crystalline. This is the reason why variation of colours are in opals.
  
• Agate is a banded microcrystalline form of the mineral Quartz, and does not occur in visible crystals. It occurs in nodules, in massive form, as botryoidal, mammilary, and stalactitic formations, as smooth rounded pebbles, as amygdules, and as the linings of geodes.
  
• Onyx is formed of bands of chalcedony in alternating colors. It is cryptocrystalline, consisting of fine intergrowths of the silica minerals quartz and moganite. Its bands are parallel to one another, as opposed to the more chaotic banding that often occurs in agates.
  
• Hence option A is correct answer.

• The phenomena of the shielding effect of electrons explains this. Since there are fewer electrons in $$Ge ^{4+}$$, the nucleus has a stronger pull on those electrons than in $$Ge ^{+2}$$.
  
•  Both $$Ge ^{4+}$$ and $$Ge ^{2+}$$ have the same stabilizing attractive force and $$Ge ^{2+}$$ has more electrons and thus more of the de-stabilizing repulsive force.So, $$Ge^{4+}$$  is more stable than $$Ge ^{2+}$$
  
• Hence option B is not correct.

• Due to Inert pair effect, in the elements which are at a lower position in a group, there are d and f orbitals which have a poor shielding effect. So outermost s electrons feel more attractions with the nucleus and become more difficult to lose. So as 2 electrons are not getting lost, oxidation state decreases from +3 to +1.
  
• Hence, $$Tl^{+}>In^{+}>Ga^{+}$$ and $$Ga^{3+}>In^{3+}>Tl^{3+}$$
  

• In group-14 the general oxidation states shown by the elements are +4,+2. The stability of +2 oxidation state increases down the group because of inert pair effect. 
  
• The reason for this is the pairing energy of the s-orbital electrons is more than the energy released during the bond formation.
  

• To treat or combine chemically an unsaturated compound with hydrogen. Liquid vegetable oils are often hydrogenated to turn them into solids. To turn coal into oil by combining its carbon with hydrogen to form hydrocarbons.
  
• In periodic table Group 7-9 elements show maximum catalytic activity in Hydrogenation reactions.
  

• Boron forms just covalent compounds while aluminium forms even some ionic compounds.
  
•  The oxides and hydroxides of boron are acidic in nature. As compared to this, the oxides and hydroxides of aluminium are amphoteric in nature. 
  

• $$CO_2$$ consists of individual molecules with one central carbon atom double bonded to two oxygen atoms. Silicon does not form double bonds with oxygen. $$CO_2$$ is gas but $$SiO_2$$ is solid because the $$SiO_2$$ is in giant molecular structure but the $$CO_2$$ is simple molecular structure.because of this reason $$CO_2$$ is gas but $$SiO_2$$ is solid.
  
• $$CO_2$$ is an acidic oxide can be explained by Lux-Flood concept & extended Lewis theory. $$CO_2$$ with $$H_2O$$ produces $$H_2CO_3$$ i.e. carbonic acid.
  
• Silicon dioxide has no basic properties - it doesn't contain oxide ions and it doesn't react with acids. Instead, it is very weakly acidic, reacting with strong bases. Silicon dioxide doesn't react with water, because of the difficulty of breaking up the giant covalent structure.
  

BF3 has trigonal planar structure all the three BF bonds lie in the plane and thus p-orbitals of boron and fluorine become parallel

Boron has empty p-orbital and p-orbital of fluorine contains lone pair and hence Boron act as Lewis acid and fluorine as Lewis base. Fluorine donates it's a lone pair to Boron and this bonding is called back bonding

So, the correct answer is 'BF3'.

Before reaction with $$HNO_3$$ it forms an oxide layer of $$Al_2O_3$$.

 oxide layer does not allow reaction of $$HNO_3$$ with Aluminium.

Because of this reason $$Al$$ vessel is used to store $$HNO_3. HNO_3$$ does'nt react with $$Al$$ Or any other metal (except manganese and magnesium) because $$HNO_3$$ is a strong oxidising agent.

Little packets of silica gel are found in all sorts of products because silica gel is a desiccant -- it adsorbs and holds water vapor. In leather products and foods like pepperoni, the lack of moisture can limit the growth of mold and reduce spoilage. In electronics it prevents condensation, which might damage the electronics. If a bottle of vitamins contained any moisture vapor and were cooled rapidly, the condensing moisture would ruin the pills. You will find little silica gel packets in anything that would be affected by excess moisture or condensation.

Silica gel is nearly harmless, which is why you find it in food products. Silica, or silicon dioxide ($$SiO_2$$), is the same material found in quartz. The gel form contains millions of tiny pores that can adsorb and hold moisture. Silica gel is essentially porous sand.