User947387
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I have enclosed some questions from chemistry higher past papers I am stuck on.

For attachment C; I thought that for question 38; I thought the answer was A; after all, hydrocarbons are made up of hydrogen and carbon, so that is covalent bonding....and the elements i.e. hydrogen and carbon do not exist by themselves...excluding Van der Waal forces (was my logic anyway).

For 39; which of the following has a covalent molecular structure, I thought the answer was B, a noble gas. A fullerene has a covalent network; A and C are both ionic compounds;

Question 40; I am baffled by. I guess that the presence of chlorine is a big clue, but for the life of me I don't know.

Attachment D; or question 46; Given that there has been 6 electrons removed; I thought that the element belonged to group 6....

How do you determine ionic character?

Attachment F; ques 57; I thought the answer was sulphur dioxide. The other three are all metal and non metals (i.e. ionic).

What IS the properties of chlorine that proves it has ionic bonding?
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HenryHiddler
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(Original post by apronedsamurai)
I have enclosed some questions from chemistry higher past papers I am stuck on.

For attachment C; I thought that for question 38; I thought the answer was A; after all, hydrocarbons are made up of hydrogen and carbon, so that is covalent bonding....and the elements i.e. hydrogen and carbon do not exist by themselves...excluding Van der Waal forces (was my logic anyway).

For 39; which of the following has a covalent molecular structure, I thought the answer was B, a noble gas. A fullerene has a covalent network; A and C are both ionic compounds;

Question 40; I am baffled by. I guess that the presence of chlorine is a big clue, but for the life of me I don't know.

Attachment D; or question 46; Given that there has been 6 electrons removed; I thought that the element belonged to group 6....

How do you determine ionic character?

Attachment F; ques 57; I thought the answer was sulphur dioxide. The other three are all metal and non metals (i.e. ionic).

What IS the properties of chlorine that proves it has ionic bonding?
  • 13: A - one of the defining properties of an ionic solid is that it conducts electricity when molten.
  • 38: During fractional distillation, the crude oil is vaporised, which breaks vdw forces. Then, as the fraction condenses, it will form a liquid, during which vdW forces will reform. Covalent bonds do NOT break, or else the fraction would no longer be a hydrocarbon, since it would separate into hydrogen and carbon
  • 39: Silicon dioxide is NOT an ionic solid. It forms a macromolecular structure.
  • 51: BeCl2. You're looking for the bonding with the most polarisation - so, you're looking for the smallest, most charged cation, and the largest, most charged anion. BeCl2 fits the bill.

Hope this helps
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User947387
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Thank you very much, that is a help, thank you.

However, I ran into difficulty again

Initially, given that we are being asked for the number of moles of sodium ions, I thought that this involve one of the "pyramids" i.e.; either m/gfm or c*v. However; We are not actually given a specific mass; nor are we given a volume or concentration rendering those two possible avenues defunct. I then thought this might be a reactant in excess question, but that didnt seem to fit either
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HenryHiddler
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You know that both are ionic compounds, right? The formula for sodium chloride is NaCl. In solution that gives NaCl > Na+ + Cl-. The ratio between NaCl, Na+ and Cl- is 1:1:1. So for each mole of NaCl, you have one mole of Na+ and one mole of Cl-. But you know that you have 0.6 mol of Cl-. So you have 0.6 mol of Na+, too.

Sodium sulfate has the formula Na2SO4. In solution, that gives Na2SO4 > 2Na+ + SO42-. So you have a 1:2:1 ratio of Na2SO4, Na+ and SO42-. But you know that you have 0.2 mol of sulfate ions. So, by the 1:2:1, you multiply the 0.2 x 2, which gives 0.4 mol Na+.

Now just add them - 0.6 + 0.4 = 1.0

Hope this helps
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User947387
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I had actually stumbled across a note from my tutor that showed the working involved. Thank you again for posting

Guys, for anyone who happens to stumble across this thread; let me make a contribution.

If you are ever asked about the ionic character of a compound, simply find the difference between the two electronegative values of the elements involved; so use your data booklet for that value and bag yourself a easy mark
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