[interesting]

Can someone please help me with the following...

State the amount of substance in:

26.5g anhydrous sodium carbonate

Can you also show workings as well please. I want to know how you got to the answer.

[Borek]

What is formula of the substance? What is its molar mass?

[interesting]

OK ive been at it and i have worked it out.lol.

NA2CO3 = 106 molar mass(this is molar mass right)

then 26.5/106 = 0.25

the mistake i was making was i missed out calculating oxygen.

[interesting]

OK im stuck on another question. Can someone help me work this out please:

Write down the mass of calcium which has the same number of atoms as 12g of magnesium.

Thanks

[BetaAmyloid]

Okay, you have 26.5 grams of anhydrous sodium carbonate. Anhydrous sodium carbonate weighs 105.9884 grams per mole.

So:

26.5 grams Na2CO3 x             1 mole Na2CO3                  = 0.250027 moles Na2CO3
                                   105.9884 grams/mole Na2CO3

Grams cancel out on the top and bottom, leaving moles.

Hope this helps,
The Cancer Curer

[Borek]

0.250027 moles

Sig figs please. Besides, that was already answered correctly.

Write down the mass of calcium which has the same number of atoms as 12g of magnesium.

How is number of moles related to number of atoms?

[interesting]

0.250027 moles

How is number of moles related to number of atoms?

Hello,

Number of atoms in one mole = 6*10^23?

 

[Borek]

6.02*10²³ to be more precise.

12 g of magnesium - how many moles?

[interesting]

6.02*10²³ to be more precise.

12 g of magnesium - how many moles?

Got it. 12/24= 1 mole then 0.5*40 = 20m

I still don't get whats happening. Is it because the number of moles in 1 atom = 6.02*10^23. And this rule is for all elements. So when I worked out what 1 mole was for 12g of Mg i just multiply it by the molar mass of calcium. Is my thinking correct or gibberish?

[Arctic-Nation]

The amount of particles (atoms, molecules, ions, subatomic particles) in one mole is a constant known as Avogadro's constant. The mass of any species amounting to one mole depends on the species and is known as the molar mass (in terms of g/mole) This allows for the interconversion between mass and moles. If you have a certain mass of particles (12 g of Mg), you can calculate the amount of moles from that (12 g/24 g/mole is 0.5 moles). If you have a certain amount of moles, you can calculate the mass from that (0.5 moles * 40 g/mole is 20 g).

Your idea is good, but you explained it incorrectly. You do not search for 'what is one mole for 12 g of Mg', but 'how many moles are in 12 g of Mg'.

[interesting]

The amount of particles (atoms, molecules, ions, subatomic particles) in one mole is a constant known as Avogadro's constant. The mass of any species amounting to one mole depends on the species and is known as the molar mass (in terms of g/mole) This allows for the interconversion between mass and moles. If you have a certain mass of particles (12 g of Mg), you can calculate the amount of moles from that (12 g/24 g/mole is 0.5 moles). If you have a certain amount of moles, you can calculate the mass from that (0.5 moles * 40 g/mole is 20 g).

Your idea is good, but you explained it incorrectly. You do not search for 'what is one mole for 12 g of Mg', but 'how many moles are in 12 g of Mg'.

Oh thanks for that, really appreciate that. And thanks to everyone else also for helping me out. This is not the last time I will need it.lol.

[interesting]

I'm working through 2 different books and the way they word the questions are different. Does substance mean the same thing as material?

Question is, whats the amount of material in:

34.0g of glucose, C6H12O6

= 34/180

=0.19mol

Is my answer correct?

[interesting]

Anyone please, help needed for above^^^^

[Borek]

Sig figs, but you are on the right track.