chemistry 1/2 questions thread

[jgoudie]

The reducing agent is called the reductant, it loses electrons in an oxidation reaction.

In an oxidation reaction electrons are lost by the reductant causing the oxidant to under go reduction and gain electrons.

Electrons are transferred from the reductant to the oxidant.

If you read through it slowly it makes sense.

I know if something is reduced, it has gained electrons but what does a reducing agent do?
Does it cause other substances to gain electrons? Or does it gain electrons itself?

thanks!

[RazzMeTazz]

The reducing agent is called the reductant, it loses electrons in an oxidation reaction.

In an oxidation reaction electrons are lost by the reductant causing the oxidant to under go reduction and gain electrons.

Electrons are transferred from the reductant to the oxidant.

If you read through it slowly it makes sense.

Thanks so much!

[Tyleralp1]

Here is a question we have to complete as part of a prac report on Determining the Empirical Formula of Magnesium Oxide...

"Nitrogen in the air may react with Magnesium. Explain how this may effect results"

Could someone please provide a nice answer to this, or at least point me in the right direction by listing a few pointers of what to mention.

Thanks!

[jgoudie]

Interesting question to ask,  Firstly remember that MgO is the correct empirical formula you are looking for.

If Magnesium reaction with nitrogen, it forms Mg₃N₂, think about the charges involved in the ionic bonding.

Now being that nitrogen is less heavy that oxygen and that the ratio is in Mg₃N₂ is more favourable to magnesium, if any magnesium forms Magnesium nitride instead of magnesium oxide, you will get less mass in your end product.

This will mean you will end up calculating less oxygen is formed than if the atmosphere was pure oxygen, this less mass will lead you to calculate a greater ratio of Magnesium to Oxygen.  So you might end up with Mg₂O or Mg₃O or Mg₃O₂ or something like that.

Hope that makes some sense.

Here is a question we have to complete as part of a prac report on Determining the Empirical Formula of Magnesium Oxide...

"Nitrogen in the air may react with Magnesium. Explain how this may effect results"

Could someone please provide a nice answer to this, or at least point me in the right direction by listing a few pointers of what to mention.

Thanks!

[Tyleralp1]

Thank you soo much!!

Also another question:

Differentiate Relative Atomic Mass, Relative Molecular Mass, Molar Mass as well as  amu, grams, grams/mol.

[RazzMeTazz]

What is the difference in the definition between a 'mole' and 'Avogadro's constant'
? I thought Avogadro came up with the mole unit..

[grannysmith]

What is the difference in the definition between a 'mole' and 'Avogadro's constant'
? I thought Avogadro came up with the mole unit..

Same thing

[alchemy]

What is the difference in the definition between a 'mole' and 'Avogadro's constant'
? I thought Avogadro came up with the mole unit..

One mole contains the same number of elementary particles (atoms) that is expressed by the number that's 'Avagadro's Constant'. So yes, "a" (one) mole is the same as Avagadro's constant, as the mole is a SI unit which measures the number of particles in a particular substance. However, 2 moles means the number (Avagadro's constant) must be doubled if you want to find the number of particles. 3 moles of a substance would contain 3 times as many particles as 1 mole, and so on...

[RazzMeTazz]

I'm kind of stuck with this question..

An oxide of Copper is heated in a stream of hydrogen until only the copper remains according ti the equation:

CuxO(s) + H2(g) --> XCu(s) + H2O(l)

the data for the experiment are given in the table below. Calculate the empirical formula of the oxide of copper.

Item and mass:
Crucible - 27.002g
Crucible plus contents before heating - 27.128g
Crucible plus contents after heating - 27.114g

[darka221]

What is the number of mole of oxygen atoms in 40 g of iron sulphate Fe^2(So4)3. Thanks in advance...

[rhinwarr]

Find the number of mole of iron sulphate with n=m/M then times it by 12 because there's 12 oxygen atoms in each iron sulphate molecule

[IndefatigableLover]

I'm kind of stuck with this question..

An oxide of Copper is heated in a stream of hydrogen until only the copper remains according ti the equation:

CuxO(s) + H2(g) --> XCu(s) + H2O(l)

the data for the experiment are given in the table below. Calculate the empirical formula of the oxide of copper.

Item and mass:
Crucible - 27.002g
Crucible plus contents before heating - 27.128g
Crucible plus contents after heating - 27.114g

Alright so if we want to find the mass of CuxO then we subtract the mass of crucible with contents before heating with crucible to find that out (27.128 - 27.002 = 0.126g)
To find the mass of copper then we subtract the other one with the mass of the crucible for the weight of Copper (27.114 - 27.002 = 0.112g).

As a result we have the masses of CuxO and Cu so now we can find the weight of oxygen (0.126-0.112=0.014g)

Now to find the empirical formula then we must find the number of moles for Copper in CuxO and the number of moles of Oxygen in CuxO. In this case we'll be dividing the masses of Copper and Oxygen by their molar mass.


Now the next step in finding the empirical formula is t divide all the amounts by the smallest number of moles. In this case we will be dividing the moles of oxygen against copper to determine our empirical formula (since it's the least).

Keeping our fractions before and dividing, you should get an answer of 256/127 which roughly translates to 2.
Therefore for every one oxygen, there are 2 copper atoms.
So then x=2.

(You can kind of see the answer since the charge of oxygen is -2 so we can assume that the charge of Copper must be equal with it).

[RazzMeTazz]

Alright so if we want to find the mass of CuxO then we subtract the mass of crucible with contents before heating with crucible to find that out (27.128 - 27.002 = 0.126g)
To find the mass of copper then we subtract the other one with the mass of the crucible for the weight of Copper (27.114 - 27.002 = 0.112g).

As a result we have the masses of CuxO and Cu so now we can find the weight of oxygen (0.126-0.112=0.014g)

Now to find the empirical formula then we must find the number of moles for Copper in CuxO and the number of moles of Oxygen in CuxO. In this case we'll be dividing the masses of Copper and Oxygen by their molar mass.

(Image removed from quote.)
Now the next step in finding the empirical formula is t divide all the amounts by the smallest number of moles. In this case we will be dividing the moles of oxygen against copper to determine our empirical formula (since it's the least).

Keeping our fractions before and dividing, you should get an answer of 256/127 which roughly translates to 2.
Therefore for every one oxygen, there are 2 copper atoms.
So then x=2.

(You can kind of see the answer since the charge of oxygen is -2 so we can assume that the charge of Copper must be equal with it).

thanks!! so much!!    great explanation!

[RazzMeTazz]

Does anybody know the answer to this question:

Naturally occuring bromine consists of two isotopes, ⁷⁹Br and ⁸¹Br. However the mass spectrum of bromine molecules, Br₂ shows three peaks at relative masses 158, 160 and 162. Give an explanation for this observation

[rhinwarr]

Since its a diatomic molecule, there are 3 combinations for the 2 different isotopes.
79Br-79Br
79Br-81Br
81Br-81Br