Can someone explain the answers please? Question 10 Silicon carbide, which has t
ID: 551558 • Letter: C
Question
Can someone explain the answers please?
Question 10 Silicon carbide, which has the empirical formula: SiC, melts at 2780 'C and is nearly as hard as boron nitride and diamond. Which category of substance does it most likely fit under? elected Answercovaent (network Answers molecular covalent [network onic amorphouS Question 11 Which of the following pairs can potentially form hydrogen bonds with each other? Selected AnswerNaCl and acatone, (CH3)2CO NaCl and acetone, (CH3)2CO CH3NH2 and CH3OCH3 NF3 and CF4 Question 12 Hydrofluoric acid, HF(aq) cannot be stored in glass bottles because compounds called silicates in the glass are attacked by the HF(aq). Sodium silicate(Na2SiO3) for example, reacts as follows Na2SiO3(s)+8 HF(aq)H2SiF a NaF(aq)3 H20) How many moles of HF are needed to react with 0.300 mol of Na2Si03? Selected Answer:24 Correct Answer: 24 Answer range0.5 1.9-2.9)Explanation / Answer
10. SiC has a diamond like tetrahedral crystal structure and thus forms covalent bond just as carbon does in diamond. In this type of Covalent solids the constituent particles are atoms of the same or different elements connected to each other by covalent bond.
So a network of covalent bonds is formed throughout the crystal and they form a giant molecule. Due to strong covalent bonds, they are hard and brittle and have high melting and boiling points. They are insulators but graphite is exception in this case because of the free fourth electron of each carbon atom where each carbon atom is linked to three neighboring carbon atoms.
11.A hydrogen bond is formed when a charged part of a molecule having polar covalent bonds forms an electrostatic (charge, as in positive attracted to negative) interaction with a substance of opposite charge. Molecules that have nonpolar covalent bonds donot form hydrogen bonds.In order for hydrogen bonds to occur hydrogens need to be bonded to an electronegative atom such as oxygen or fluorine. This is the only case possible in CH3NH2 and CH3OCH3, where -H is attached to N atom and makes hydrogen bond with O- atom.
12.
1 mole of Na2SiO3 reacts with 8 moles of HF to form products. For 0.3 mole of Na2SiO3 ,
Moles of HF required = 0.3 x 8 = 2.4 moles