Rod's Chemistry 3/4 Questions Thread

[Rod]

oh yeah...makes more sense now. Sorry for the wrong answer Rod and nhmn0301

All good Rishi! Thanks heaps for trying , you got us there. Lets try and figure out the other two!

[nhmn0301]

Question 2:
So because this is a mixture of both CaCO3 and CaO and if you look at the equation, there is CO2 presents, which is a gas. When you get this compound up, CO2 will escape, which accounts for the mass loss. Hence, 0.572 is the mass of CO2, hence mole of CO2 is 0.013 mole. Now the Carbon in CO2 would give us the mole of CaCO3, hence the mass of CaCO3 is 1.3013g. Substrate mass of CaCO3 from the sample we have the mass of CaO, which is 0.5277g. Hence, percentage by mass of CaCO3 is 29.3%

[Rod]

Let me have a shot at the other two, let's try and figure them out.

2)
Still have no clue.

3)
n(h2O) = 18/18 = 1 mol
n(h) = 1x2 = 2 mol

m(hydrocarbon) = 11g
m(carbon in hydrocarbon) = 11 - 2x1 = 9g
n (carbon) = 9/12 = 0.75

C:             0.75/0.75                           H: 2/0.75

=               1                         :             2.67

x3            C3H8

Yay!

[Rod]

Question 2:
So because this is a mixture of both CaCO3 and CaO and if you look at the equation, there is CO2 presents, which is a gas. When you get this compound up, CO2 will escape, which accounts for the mass loss. Hence, 0.572 is the mass of CO2, hence mole of CO2 is 0.013 mole. Now the Carbon in CO2 would give us the mole of CaCO3, hence the mass of CaCO3 is 1.3013g. Substrate mass of CaCO3 from the sample we have the mass of CaO, which is 0.5277g. Hence, percentage by mass of CaCO3 is 29.3%

Thanks man, I've just figured out question three if you want to take a look at it

[Rishi97]

Thanks man, I've just figured out question three if you want to take a look at it

same !!!! Yay, first success of the night

[Rod]

Question 2:
So because this is a mixture of both CaCO3 and CaO and if you look at the equation, there is CO2 presents, which is a gas. When you get this compound up, CO2 will escape, which accounts for the mass loss. Hence, 0.572 is the mass of CO2, hence mole of CO2 is 0.013 mole. Now the Carbon in CO2 would give us the mole of CaCO3, hence the mass of CaCO3 is 1.3013g. Substrate mass of CaCO3 from the sample we have the mass of CaO, which is 0.5277g. Hence, percentage by mass of CaCO3 is 29.3%

So:

Assume that 0.572 g was lost to CO2

n(c02) = 0.572/44 = 0.013 mol

n(c) = 0.013 mol

And then what did you do? Sorry.

[nhmn0301]

So:

Assume that 0.572 g was lost to CO2

n(c02) = 0.572/44 = 0.013 mol

n(c) = 0.013 mol

And then what did you do? Sorry.

Sorry for the crappy working out, I was in a rush, you got the mole of Carbon in CO2, because CaCO3 is the only compound in that mixture that contains Carbon, you can assume that this amount of Carbon is from the CaCO3, hence, mole of ( C ) = mole ( CaCO3 ). Hence, mass of CaCO3 = 0.013 = 1.3 (g).
mass of CaO = mass of compound - 1.3
then find percentage by mass
sorry for the confusions.

[Rod]

Hey guys just confirming that colorimetry is no longer in the course?

[Edward21]

Hey guys just confirming that colorimetry is no longer in the course?

Well it's more of less a cheap version of UV-Vis focussing only on the visible part haha. Doesn't hurt to know, but UV-Vis is what will be examined

[Rod]

Well it's more of less a cheap version of UV-Vis focussing only on the visible part haha. Doesn't hurt to know, but UV-Vis is what will be examined

Thanks pal

[Rod]

Some questions here;

Some questions on NMR spectroscopy;

How come CH3F would have a larger chemical shift than CH3I? Fluorine has a smaller molecular mass than iodine, but how does that relate?

Does NMR essential look at the arrangement of bonding electrons around the nucleus being investigated??

And one more question on mass spec;

I get how ions with smaller masses will deflect more as they pass through a magnetic field, but how come a small charge ratio contributes even more to the deflection?

Thanks

[Rishi97]

Some questions here;

Some questions on NMR spectroscopy;

How come CH3F would have a larger chemical shift than CH3I? Fluorine has a smaller molecular mass than iodine, but how does that relate?

Thanks

It's because fluorine is more electronegative than Iodine. The more electronegative elements have a greater chemical shift so they are often towards the left side of the graph

[thushan]

Almost. The fluorine atom is highly electronegative yes, which pulls negative charge away from the C atom. In turn, the C atom will tend to pull some negative charge away from the H atoms, deshielding the H atoms. Increased chemical shifts are associated with greater de-shielding.

[lzxnl]

Some questions here;

Some questions on NMR spectroscopy;

How come CH3F would have a larger chemical shift than CH3I? Fluorine has a smaller molecular mass than iodine, but how does that relate?

Does NMR essential look at the arrangement of bonding electrons around the nucleus being investigated??

And one more question on mass spec;

I get how ions with smaller masses will deflect more as they pass through a magnetic field, but how come a small charge ratio contributes even more to the deflection?

Thanks

In physics, the magnetic force is given by qvB, where q is the charge, v is the speed and B is the magnetic field (only if the field is perpendicular to the direction of motion; don't worry about that here)
So using Newton's second law for uniform circular motion (yes, the magnetic force is always perpendicular to the direction of motion so it satisfies the direction requirement for circular motion), mv^2/r = qvB
r = mv/qB
See how m/q determines the radius of the circular motion?

[Rod]

Crap, last post 50 days ago! Doesn't vce go fast!!

Having a hard time getting my head around the effects of changing pressure in a reaction;

So apparently, with any change in pressure, the reaction will oppose it by moving to the side with less gas particles. Not sure what it means by 'moving to the side with less gas particles'. Does it mean just move to the side of the reaction with less coefficients?

Don't understand the whole theory of pressure vs reaction