Prelim Chem Thread (2 Viewers)

[eyeseeyou]

What about the example of rusting?

 

[1008]

Rusting is also a redox reaction, where iron is oxidised (loses electrons), which are transferred to oxygen to create O^(2-). The Fe(2+) and P(2_0 combine to form ferrous oxide, aka rust

 

[eyeseeyou]

Rusting is also a redox reaction, where iron is oxidised (loses electrons), which are transferred to oxygen to create O^(2-). The Fe(2+) and P(2_0 combine to form ferrous oxide, aka rust

Once again thanks

 

[1008]

Once again thanks

Sorry for the typo, its meant to be o(2-) not P(2_0

 

[eyeseeyou]

Sorry for the typo, its meant to be o(2-) not P(2_0

What?

 

[1008]

Rusting is also a redox reaction, where iron is oxidised (loses electrons), which are transferred to oxygen to create O^(2-). The Fe(2+) and P(2_0 combine to form ferrous oxide, aka rust

That's a typo.

 

[eyeseeyou]

What are the solubility rules in the water topic?

hey whats the trend of melting and boiling point on the periodic table for metals, non metals and semi as we go down and across?

anyone know the trend??

2. Pure substances have a constant, definite composition. Why? It cannot be separated into simpler substances by physical means. Why?
3. If there is an imbalance in chemical equation, why would we need to add extra numbers in order to balance it?
4. Why is sodium+hydrochloric acidSodium chrloride+hydrogen gas
5. Why does delta H represent a change in heat energy (enthalpy)?
6. Why does delta H < 0 represent heat energy released (exothermic)?
7. Why does delta H>0 represent heat energy absorbed (endothermic)?
8. Why are elements considered the simplest substances which cannot be broken down into further physical and chemical means?
9. Why are elements made up of only one type of atom?
10. Why are all known elements listed on the periodic table?

11. A compound is a pur substance that is made from more than one atom chemically joined together in a fixed ratio. Why?
12. Why do compounds have a molecular formula?
13. Why do compounds be decomposed into its elements by chemical means?
14. Why do compounds display different chemical and physical properties compares to the elements they are made from?
15. Why are mixtures impure?
16. Why do mixtures consist of 2 or more substances?
17. Their composition is not fixed as the components can be present in varying proportions (of mixtures). Why?
18. Why can the different omponents be separated by using physical separating techniques?
19. Why can mixtures not be represented using a chemical formula?
20. Why can mixtures be classified as homogenous or heterogenous?

21. Why does a homogenous mixture have a uniform composition and properties throughout?
22. Why are the molecules (in a homogenous mixture) evenly mixed throughout?
23. Why does a heterogeneous mixture have a variable composition and properties throughout?
24. Why is the biosphere where living organisms found?
25. Why are living things composed of cells and within these cells, there are many compounds and elements such as carbohydrates, fats, and proteins?
26. The most common elements found in the body are carbon, hydrogen, oxygen, nitrogen, phosphorus and sulfur. Why?
27. In the body there are a range of carbohydrates, proteins and fats. Why? (this is regarding mixtures)
28. The lithosphere includes the earth’s uppermost solid mantle and the crust. Why?
29. The lithosphere consists mainly mixtues of different of different mineral sediment with sand, rock and soils oxides and oxygen compounds? Why? These substances make up the mixtre? Why?
30. Why does the hydrosohere include all the waters on the earth’s surface. i.e. oceans, rivers, lakegroundwater and atmospheric mixture?

31. Why is water the most abundant compound in this atmosphere?
32. Why does the sea contain many dissolved minerals and salts?
33. Why is a sieve a tool that has many small holes?
34. Why is it usred to separate smaller particles from larger ones or solids from liquids?
35. When sieving, why are components separated based upon different particle size?
36. In sieving, why do the larger particles get trapped in the sieve while the smaller particles are able to pass through?
37. In magnetic separation, why is it strictly separated based on particle size?
38. Why in magnetic separation, the separation is based on ferromagnetism?
39. Why is ferromagnetism the basic magnetic property where a substance is naturally attracted to a magnet?
40. When the magnet is stirred around in the mixture, ferromagnetic substances will attract to the magnet. Why?

41. Sedimentation is based upon the density of the compounds. Why?
42. Why will the heavier solids sink to the bottom of the container?
43. Why would decantation follow sedimentation (in that sense if you get what I mean)?
44. Why is the solid left behind when the liquid is poured out from the container?
45. Why is filtration based on the insolubility of the components and particle size?
46. When the mixture is poured through the liquid, the liquid passes through and is known as the filtrate while the solid is left behind in the filter paper (the residue). Why?
47. Centrifugation is separating substances based upon density and immiscibility. Why?
48. Why is centrifugation a process which involves the use of the centrifugal force for the sedimentation of heterogeneous mixtures?
49. Why (in centrifugation) is the force produced causes the suspended substances to sink to the bottom where the substances at the bottom are denser?
50. Why is this process usually used to separate blood into different components?

51. In evaporation, the mixtures are separated based upon boiling point. Why?
52. Why in evaporation, would the more volatile boiling point evaporate first?
53. Why does high volatily=low boiling point?
54. Why is crystallisation separated based on solubility?
55. Why is crystallisation conducted when the solution contains more than one solute?
56. Why do different solutes have varying degrees of solubility?
57. Why would different solutes crystallise at different times when the liquid evaporates?
58. Why would substances with a low solubility crystallise first?
59. Why does distillation use boiling points to separate?
60. In distillation ,why would the more volatile liquid evaporate and travel up the column into the condenser where it is condensed back into liquid form and is collected in a separate beaker?

61. Why is fractional distillation used when liquids have similar boiling points?
62. Why does fractionating column allow for there to be multiple condensations?
63. Why does the more volatile substances condense first and reach the top of the fractionating column?
64. Why does the higher boiling point substance vaporise and condenses more readily in the fractionating column and drips back into the distilling flask?
65. Why does a separating funnel separate immiscible liquids based upon density?
66. Why is the mixture that is formed heterogenous and why are there two layers?
67. Why is the denser layer at the bottom?

I'd be a shame if no one answered these q's

 

[InteGrand]

I'd be a shame if no one answered these q's

Didn't I already answer most of them in two words ("by inspection")?

 

[eyeseeyou]

Hey guys, I have a couple questions I'm kinda stuck on:

1. What steel products can be recycled relatively easily

2. Large quantities of lead are recycled. From what products is lead most easily recycled?

3. Why is it difficult to recycle zinc?

I have some ideas, but I'm not confident at all that they're right.

1. Steel products that have been galvanised so no rusting (or much less) occurs, and so it can be put back into use more easily. I was also thinking if during the recycling process they changed alloys (say from mild steel to stainless steel or something) steels with higher concentrations of iron would be more easily recycled (as it has less impurities and can be mixed with other materials more easily), but then I though that there is absolutely no reason to change alloys during recycling, so I think that is wrong.

2. I was thinking lead would be most easily recycled in products with other low reactivity materials (so the lead doesn't react) and materials with higher concentrations of lead would also be most easily recycled I (just thinking that because maybe lead is purified again for use in other products when it is recycled? I don't really know.)

3. I didn't really have an answer at all for this, if it was an exam I would have put something like "Zinc is fairly reactive and so it can react with other materials in the products it is used in, and so to extract it more energy is required (as chemical bonds have formed, and physical separation will not suffice). Also, zinc is usually less prominent in alloys and other products, which makes it harder to recycle."

Please help with these questions. Thanks!

Also another unanswered question

 

[eyeseeyou]

Didn't I already answer most of them in two words ("by inspection")?

GIve me an example

 

[InteGrand]

GIve me an example

Here is where:

Most of your Q's can be answered in two words: "by inspection".

.

 

[eyeseeyou]

Here is where:

.

No I meant give me an example of how you woudl nswer my question(s)

 

[InteGrand]

No I meant give me an example of how you woudl nswer my question(s)

I would probably answer your questions by saying "by inspection".

 

[eyeseeyou]

Why are mixtures impure?

 

[1008]

Why are mixtures impure?

A pure substance is a material that is composed of only one type of particle; examples of a pure substance include gold, oxygen and water.

A mixture is made of more than one type of particle, so it is impure

 

[Nailgun]

I'd be a shame if no one answered these q's

 

[eyeseeyou]

Need help with chemical equations:

1. heating potassium chlorate, KCLO3, to form solid potassium chloride and oxygen gas
2. reacting aluminium with aqueous hydrochloric acid, HCL, to produce aqueous aluminium chlirode and hydrogen gas
3. Burning Hydrogen sulfide gas in oxygen to form gaseous sulfur dioxide and gaseous water
4. CO+O2--->C02. This took me a while to solve properly (I solved it by asking someone for their answers and I don't really want to do that)
5. Na+H2O--->NaOH+H2. For some reason, when I am adding all these numbers and trying to balance the chemical equation, I am still not able to balance it and I've spent a while doing that
6.HCL+AL--->AlCl3+H2. Same reason as 5
7. Nitirc acid+sodium hydroxide
8. Sulphuric acid+magnesium
9. Hydrochloric acid+magnesium oxide
11. Sulphuric acid+calcium oxide
12. Hydrochloric acid+magnesium carbonate
13. Nitric acid+aluminium bicarbonate

 

[Shuuya]

Need help with chemical equations:

1. heating potassium chlorate, KCLO3, to form solid potassium chloride and oxygen gas
2. reacting aluminium with aqueous hydrochloric acid, HCL, to produce aqueous aluminium chlirode and hydrogen gas
3. Burning Hydrogen sulfide gas in oxygen to form gaseous sulfur dioxide and gaseous water
4. CO+O2--->C02. This took me a while to solve properly (I solved it by asking someone for their answers and I don't really want to do that)
5. Na+H2O--->NaOH+H2. For some reason, when I am adding all these numbers and trying to balance the chemical equation, I am still not able to balance it and I've spent a while doing that
6.HCL+AL--->AlCl3+H2. Same reason as 5
7. Nitirc acid+sodium hydroxide
8. Sulphuric acid+magnesium
9. Hydrochloric acid+magnesium oxide
11. Sulphuric acid+calcium oxide
12. Hydrochloric acid+magnesium carbonate
13. Nitric acid+aluminium bicarbonate

For the first three, do you want help balancing? Because the equation is already in the question lol.

5. 2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g)
6. 6HCl(aq) + 2Al(s) → 2Al₃Cl₃(aq) + 3H₂(g)
7. HNO₃(aq) + NaOH(aq) → NaNO₃(aq) + H₂O(l)
8. H₂SO₄(aq) + Mg(s) → MgSO₄(aq) + H₂(g)
9. 2HCl(aq) + MgO(s) → MgCl₂(aq) + H₂O(l)
11. H₂SO₄(aq) + CaO(s) → CaSO₄(s) + H₂O(l)
12. 2HCl(aq) + MgCO₃(aq) → MgCl₂(aq) + CO₂(g) + H₂O(l)
13. 3HNO₃(aq) + Al(HCO₃)₃(aq) → Al(NO₃)₃(aq) + 3CO₂(g) + 3H₂O(l)

Now please stop asking me to do your questions

 

[eyeseeyou]

For the first three, do you want help balancing? Because the equation is already in the question lol.

5. 2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g)
6. 6HCl(aq) + 2Al(s) → 2Al₃Cl₃(aq) + 3H₂(g)
7. HNO₃(aq) + NaOH(aq) → NaNO₃(aq) + H₂O(l)
8. H₂SO₄(aq) + Mg(s) → MgSO₄(aq) + H₂(g)
9. 2HCl(aq) + MgO(s) → MgCl₂(aq) + H₂O(l)
11. H₂SO₄(aq) + CaO(s) → CaSO₄(s) + H₂O(l)
12. 2HCl(aq) + MgCO₃(aq) → MgCl₂(aq) + CO₂(g) + H₂O(l)
13. 3HNO₃(aq) + Al(HCO₃)₃(aq) → Al(NO₃)₃(aq) + 3CO₂(g) + 3H₂O(l)

Now please stop asking me to do your questions

Yes first 4 actually

 

[eyeseeyou]

For the first three, do you want help balancing? Because the equation is already in the question lol.

5. 2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g)
6. 6HCl(aq) + 2Al(s) → 2Al₃Cl₃(aq) + 3H₂(g)
7. HNO₃(aq) + NaOH(aq) → NaNO₃(aq) + H₂O(l)
8. H₂SO₄(aq) + Mg(s) → MgSO₄(aq) + H₂(g)
9. 2HCl(aq) + MgO(s) → MgCl₂(aq) + H₂O(l)
11. H₂SO₄(aq) + CaO(s) → CaSO₄(s) + H₂O(l)
12. 2HCl(aq) + MgCO₃(aq) → MgCl₂(aq) + CO₂(g) + H₂O(l)
13. 3HNO₃(aq) + Al(HCO₃)₃(aq) → Al(NO₃)₃(aq) + 3CO₂(g) + 3H₂O(l)

Now please stop asking me to do your questions

Thanks Shuuya