VCE Chemistry Question Thread

[Scooby]

Thanks for clarifying that Scooby.

No problem

Help pls
1-propylamine may be produced by a reaction between 1-chloropropane and one other molecular compound. When 2.17g of 1-chloropropane is completely converted to 1-propylamine, what mass of the other compound would be expected to react?

To produce propan-1-amine from 1-chloropropane we need to react it with ammonia. Use the mass of 1-chloropropane given and its molar mass to find the number of moles of it that reacted. From that determine the number of moles of ammonia that reacted. Since you have the number of moles of ammonia reacted and its molar mass, you can work out the mass that reacted as well

[Blondie21]

is 0.025mg/L of Ca²⁺ equal to 6.25x10^-7mol L

[Yacoubb]

is 0.025mg/L of Ca²⁺ equal to 6.25x10^-7mol L

Yes.

0.025 mg/L (or ppm) / 1000 = 0.000025 g/L
0.000025 g/L divided by 40.1 (Mr of Ca) = 6.25 x 10^-7 mol/L or M.

[Blondie21]

Yes.

0.025 mg/L (or ppm) / 1000 = 0.000025 g/L
0.000025 g/L divided by 40.1 (Mr of Ca) = 6.25 x 10^-7 mol/L or M.

Wooo!! Thanks

[Rishi97]

Can anyone name and similarities or differences between IR spec, AAS and UV-visible spectroscopy?

[bonappler]

Yeah I need help with this
Grains of fine California beach sand are approximately spheres with an average radius of 50 μm and are made of silicon dioxide, which has a density of 2.8 × 103 kg/m3. What mass of sand grains would have a total surface area (the total area of all the individual spheres) equal to the surface area of a cube 0.9 m on an edge?

[Aurelian]

Yeah I need help with this
Grains of fine California beach sand are approximately spheres with an average radius of 50 μm and are made of silicon dioxide, which has a density of 2.8 × 103 kg/m3. What mass of sand grains would have a total surface area (the total area of all the individual spheres) equal to the surface area of a cube 0.9 m on an edge?

Lol what a bizarre question. Okay so, firstly think about what the surface area of that cube is going to be. Then think about what the surface area of an individual grain of sand is going to be. Then figure out how many grains of sand you're going to need.

Then think about what the mass of an individual grain of sand is going to be (hint: use the density). Then, the mass of sand you'll need will just be the number of grains required multiplied by the mass of each grain...!

Does that help? =)

[bonappler]

Actually, I got an answer but I'm not sure if it is correct

[Rishi97]

Has anyone had a chemistry sac on spectroscopy?

[soNasty]

this may sound stupid but whats the difference between Mol/L and Molarity (concentration)

just say you had a substance and it was 6.5mol/L and you wanted to find the mass...
would you go m(substance)=6.5 x (molar mass of substance)   ?

[RKTR]

For your first question,those two are the same.

Concentration(g/L)=molarity (mol/L) x molar mass (g/mol)

Then you need the volume to find the mass

Sometimes if you can't remember the formula, try using the units to help you

[soNasty]

Can someone give me the half equation of the oxidation of ethanol to ethanal?
Or, if that's not possible, the full equation of ethanol being oxidised to ethanal using an excess of potassium dichromate, please.

[lzxnl]

Can someone give me the half equation of the oxidation of ethanol to ethanal?
Or, if that's not possible, the full equation of ethanol being oxidised to ethanal using an excess of potassium dichromate, please.

Ethanol is C2H5OH
Ethanal is C2H4O

So really it's just C2H5OH => C2H4O + 2H+ + 2e-

[Snorlax]

Why is a fine layer of powder (Alumina) spread on a glass/plastic plate in Thin-Layer Chromatography?
Is it to increase surface area for components to be adsorbed into the stationary phase more effectively?

Also in chromatography, when it says you need an appropriate solvent/mobile phase what does that mean? - So, say my sample is a polar compound, would I want a polar solvent, or what? (polar-attracts-polar rule?)

Also! Does the degree of adsorption to the stationary phase depend on the: chemical structure of the stationary phase? or is it the chemical structure of the component?

Thanks,

[Rishi97]

In chromatography, are the Rf values and the Rt value, inversely proportional?