Prelim 2015 Chit Chat Thread (1 Viewer)

MilkyCat_ · Aug 22, 2015

In the equation they have the same molar ratio
Number of moles of chalcopyrite=1000000/183.54
=5448.4 moles
Therefore number of moles of copper=5448.4
5448.4=mass of copper/63.55
Therefore mass of copper=346246.05g
=346.25kg

Hope I'm right lol

Ambility · Aug 22, 2015

MilkyCat_ said:
In the equation they have the same molar ratio
Number of moles of chalcopyrite=1000000/183.54
=5448.4 moles
Therefore number of moles of copper=5448.4
5448.4=mass of copper/63.55
Therefore mass of copper=346246.05g
=346.25kg

Hope I'm right lol

That is correct!

Next question! (chemistry again):
Identify the missing products, then balance the equation:
$MgCO_3+HCl\to MgCl_2+X+Y$

DatAtarLyfe · Aug 22, 2015

Sien said:
is parametrics just a year 11 topic or does go deeper into yr 12?

But you need parametrics for conics if u do 4u

DatAtarLyfe · Aug 22, 2015

Ambility said:
That is correct!

Next question! (chemistry again):
Identify the missing products, then balance the equation:
$MgCO_3+HCl\to MgCl_2+X+Y$

$MgCO_3+2HCl\to MgCl_2+H_2O+CO_2$

Next question:

MilkyCat_ · Aug 22, 2015

DatAtarLyfe said:
$MgCO_3+2HCl\to MgCl_2+H_2O+CO_2$

Next question:
View attachment 32313

I didn't know this reaction before now

Sien · Aug 22, 2015

MilkyCat_ said:
I didn't know this reaction before now

It's a rule that with hcl will always have h2o and co2 as products (if I remember correctly )

Ambility · Aug 22, 2015

MilkyCat_ said:
I didn't know this reaction before now

Yeah an acid plus a carbonate always gives salt, water and carbon dioxide.

DatAtarLyfe, I'm working on your question. I can get the first two parts out, but the last one is giving me trouble.

Sien · Aug 22, 2015

What's a fix circle

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MilkyCat_ · Aug 22, 2015

Sien said:
It's a rule that with hcl will always have h2o and co2 as products (if I remember correctly )

nah because neutralisation reactions

rand_althor · Aug 22, 2015

MilkyCat_ said:
I didn't know this reaction before now

A useful mnemonic is CAWCS: Carbonate + Acid -> Water + Carbon dioxide + Salt

Ambility · Aug 22, 2015

It's getting late, I'm just going to dump my working, tell me if I got close.

$P(2at,at^2)\,\,\,\,\,S(0,a)\,\,\,\,\,t^2:1\\\text{By the division into ratios formula:}\\x=\frac{t^2(0)+1(2at)}{1+t^2}=\frac{2at}{1+t^2}\\y=\frac{t^2(a)+1(at^2)}{1+t^2}=\frac{at^2+at^2}{1+t^2}=\frac{2at^2}{1+t^2}\\\\m=\frac{y_1-y_2}{x_1-x_2}=\frac{\frac{2at^2}{1+t^2}-0}{\frac{2at}{1+t^2}-0}=\frac{2at^2}{2at}=t\\\\t=\frac{y}{x}$

$y=\frac{\frac{2ay^2}{x^2}}{\frac{x^2+y^2}{x^2}}$

$=\frac{2ay^2}{x^2+y^2}\\x^2+y^2=2ay$

So as you can see, I can only get a circle with radius root 2ay. I don't know how you'd get a circle with radius a.

rand_althor · Aug 22, 2015

Ambility said:
So as you can see, I can only get a circle with radius root 2ay. I don't know how you'd get a circle with radius a.

You're pretty close. The radius is a constant term (it doesn't involve y) so it isn't $\sqrt{2ay}$ . What would you do if you were required to change $x^2-4x+y^2=0$ to the general equation of a circle?

Ambility · Aug 22, 2015

rand_althor said:
You're pretty close. The radius is a constant term (it doesn't involve y) so it isn't $\sqrt{2ay}$ . What would you do if you were required to change $x^2-4x+y^2=0$ to the general equation of a circle?

Thank you! I would complete the square!

$x^2+y^2-2ay=0\\x^2+y^2-2ay+a^2=a^2\\x^2+(y-a)^2=a^2$

I guess I better post another question, though I can't be bothered finding one, so I'm making this up on the fly. I believe it is possible.

PHYSICS: A car travelling at 40km/h west collides with a van travelling at 75km/h east. The resultant wreck travels eastbound at 10km/h. If the van's mass was 1500kg, what was the mass of the car?

rand_althor · Aug 23, 2015

Ambility said:
Thank you! I would complete the square!

$x^2+y^2-2ay=0\\x^2+y^2-2ay+a^2=a^2\\x^2+(y-a)^2=a^2$

No worries

. But don't forget the restrictions of the locus. This is question 13 (c) (iii) from the 2014 HSC Extension 1 Paper, so if you can't figure it out have a read of Carrotsticks' solutions (page 10): https://www.dropbox.com/s/zt96vjplroj5xtm/HSC 2014 Extension 1 Solutions.pdf?dl=0

MilkyCat_ · Aug 23, 2015

The feels when you have to study for english

DatAtarLyfe · Aug 23, 2015

MilkyCat_ said:
The feels when you have to study for english

Lol, english is balls

Sien · Aug 23, 2015

How long are your essays usually?

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Ambility · Aug 23, 2015

Sien said:
How long are your essays usually?

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800-900 words. I mean you have to write it in 40 minutes, usually.

DatAtarLyfe · Aug 24, 2015

^same about 800. Can go more if i have it prepared beforehand

Graceuf · Aug 24, 2015

Should I be concerned that half of that maths stuff just went over my head?

Although I'm fairly sure we're doing Locus Week 10 after exams.

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