need chem help! (1 Viewer)

[jellybelly59]

An oxide of chlorine is formed by the reaction of chlorine and oxygen. In an experiment, 200mL of chlorine was reacted with 1000mL of oxygen. After reaction was finished, 300mL of oxygen was left over mixed with 200mL of the oxide of chlorine.
Apply this information to find the formula of the chlorine oxide.

Oh and this question i think i have the answer but our "great" teacher didn't give us solutions after we told her we need them to check our answers so here is the question.

Consider the reaction between sodium and excess dilute nitric acid.
Calculate the volume of gas produced at 25 degress celsius and 100kPa from 2.3 grams of sodium and calculate the number of molecules of gas produced.

and umm... does anyone have an outline for the modern development of the periodic table...? i hate being tested history questions in science subjects >.<"

 

[jellybelly59]

bump

 

[zzzz12345]

An oxide of chlorine is formed by the reaction of chlorine and oxygen. In an experiment, 200mL of chlorine was reacted with 1000mL of oxygen. After reaction was finished, 300mL of oxygen was left over mixed with 200mL of the oxide of chlorine.
Apply this information to find the formula of the chlorine oxide.

Oh and this question i think i have the answer but our "great" teacher didn't give us solutions after we told her we need them to check our answers so here is the question.

Consider the reaction between sodium and excess dilute nitric acid.
Calculate the volume of gas produced at 25 degress celsius and 100kPa from 2.3 grams of sodium and calculate the number of molecules of gas produced.

and umm... does anyone have an outline for the modern development of the periodic table...? i hate being tested history questions in science subjects >.<"

Well for the first question you would use Avogadro's Law (equal volumes of gases under the same condition of temperature and contain the same number of particles). The easiest way to do this is to construct an equation and notate the number of Cl and O atoms as x and y respectively.
I.e. 2Cl2 + 10O2 ----> 2ClxOy + 3O2
(You get the coefficients from the volumes in the question)
After doing this you use the law of conservation of mass to figure out x and y. I.e. x=2 and y=7
Therefore the formula is Cl2O7
For the second question you should start with an equation:
2Na + 2HNO3 ----> 2NaNO3 + H2
We then calculate the number of moles of sodium:
n(Na)=2.3/22.99
=0.1 moles
From the equation we can see that 0.05 moles of H2 will be produced.
Using this number we know that the volume of gas produced is=0.05 x 24.79 and thus the volume is: 1.24L (2dp)
To calculate molecules it should just be 0.05 x 6.022 x 10^23 which equates to around 3.011 x 10^22 molecules
For your final question; there should be some decent notes in the resources section on bored of studies. But generally you should know about:
-Lavosier
-Dobereiner
-Newlands
-Mendeleev
-Moseley
And maybe about Dalton if you want to mention the atomic theory.
Hope this helps somewhat

 

[12o9]

Development of the Periodic Table
Johann Dobereiner (1780-1849)
In 1829, when 40 elements were known, Dobereiner noticed that these known elements could be grouped in groups of 3, Triads.
·[FONT=&quot] [/FONT]These triads shared similar physical and chemical properties
[FONT=&quot]o[FONT=&quot] [/FONT][/FONT]Chlorine, Bromine, Iodine
[FONT=&quot]o[FONT=&quot] [/FONT][/FONT]Calcium, Strontium, Barium
[FONT=&quot]o[FONT=&quot] [/FONT][/FONT]Lithium, Sodium, Potassium
·[FONT=&quot] [/FONT]He noticed that if the elements in a triad were arranged in order of atomic mass:
[FONT=&quot]o[FONT=&quot] [/FONT][/FONT]The middle element had properties intermediate between the other two
[FONT=&quot]o[FONT=&quot] [/FONT][/FONT]The atomic mass of the middle element was nearly the same as the average of the other two
·[FONT=&quot] [/FONT]INADEQUATE – Not all elements belonged to a triad.
Contribution – Recognized that elements could be grouped according to physical and chemical properties
John Newlands (1837-1898)
1964- 60+ elements of known atomic mass
·[FONT=&quot] [/FONT]Newlands observed that properties of elements varied periodically with atomic mass
·[FONT=&quot] [/FONT]Published the law of octaves
[FONT=&quot]o[FONT=&quot] [/FONT][/FONT]Elements resembled other elements eight positions apart
[FONT=&quot]o[FONT=&quot] [/FONT][/FONT]Every eight element should be like the first element, much like the octave of music
[FONT=&quot]o[FONT=&quot] [/FONT][/FONT]Periodic properties repeated each 7 elements
·[FONT=&quot] [/FONT]INADEQUATE – Not all elements could be put into octaves
Contribution – First to clearly recognize the periodicity of properties via atomic mass
Dmitri Mendeleev (1834-1907)
1869
·[FONT=&quot] [/FONT]Published periodic table of 63 elements in order of atomic mass ( Similar chemical properties)
[FONT=&quot]o[FONT=&quot] [/FONT][/FONT]Elements with similar properties were arranged in vertical columns
·[FONT=&quot] [/FONT]Proposed periodic law
[FONT=&quot]o[FONT=&quot] [/FONT][/FONT]‘Properties of elements vary periodically with their atomic mass
·[FONT=&quot] [/FONT]Left gaps in his periodic table assuming that some elements had not been discovered yet
·[FONT=&quot] [/FONT]As time passed and atomic masses became more accurately known, some discrepancies emerged in Mendeleev’s table.
[FONT=&quot]o[FONT=&quot] [/FONT][/FONT]At times it was necessary to invert the order of atomic masses to make the elements fit
Contribution – Recognised that there were probably elements in existence that were not discovered at the time

Henry Moseley (1887-1915)
1913
·[FONT=&quot] [/FONT]Moseley clarified the irregularities in Mendeleev’s table
·[FONT=&quot] [/FONT]Moseley determined the atomic number of each element
·[FONT=&quot] [/FONT]Proposed that the atomic number, rather than atomic mass, was what determined the properties of elements
·[FONT=&quot] [/FONT]Proposed modified periodic law:
[FONT=&quot]o[FONT=&quot] [/FONT][/FONT]Properties of elements vary periodically with their atomic number
Once it was recognized that properties were dependent upon the atomic number, in turn the number of electrons, the periodic table was devised according to the electron configuration of elements


From my notes .

 

[jellybelly59]

Well for the first question you would use Avogadro's Law (equal volumes of gases under the same condition of temperature and contain the same number of particles). The easiest way to do this is to construct an equation and notate the number of Cl and O atoms as x and y respectively.
I.e. 2Cl2 + 10O2 ----> 2ClxOy + 3O2
(You get the coefficients from the volumes in the question)
After doing this you use the law of conservation of mass to figure out x and y. I.e. x=2 and y=7
Therefore the formula is Cl2O7
For the second question you should start with an equation:
2Na + 2HNO3 ----> 2NaNO3 + H2
We then calculate the number of moles of sodium:
n(Na)=2.3/22.99
=0.1 moles
From the equation we can see that 0.05 moles of H2 will be produced.
Using this number we know that the volume of gas produced is=0.05 x 24.79 and thus the volume is: 1.24L (2dp)
To calculate molecules it should just be 0.05 x 6.022 x 10^23 which equates to around 3.011 x 10^22 molecules
For your final question; there should be some decent notes in the resources section on bored of studies. But generally you should know about:
-Lavosier
-Dobereiner
-Newlands
-Mendeleev
-Moseley
And maybe about Dalton if you want to mention the atomic theory.
Hope this helps somewhat

but that seems weird because isn't the valency of oxygen 2- and chloride 1-.... How would chlorine and oxygen bond together then?

 

[ratcher0071]

but that seems weird because isn't the valency of oxygen 2- and chloride 1-.... How would chlorine and oxygen bond together then?

Since oxygen and chlorine a both gases, they bond covalently in the ratio
1 oxygen : 2 chlorine

 

[jellybelly59]

Since oxygen and chlorine a both gases, they bond covalently in the ratio
1 oxygen : 2 chlorine

but what zzzz12345 said was that it was Cl207 so how could it bond in the ratio of 1:2. Oh and I forgot to say thanks to all posters including zzzzz12345 , 12o9 and rathcher

 

[ratcher0071]

but what zzzz12345 said was that it was Cl207 so how could it bond in the ratio of 1:2

I don't know what zzzz12345 was on about

 

[zzzz12345]

I don't know what zzzz12345 was on about

I thought it looked weird too; but you can't just assume that it's Cl2O; that defies the law of conservation of mass if you look at the equation. I looked up Cl2O7 and it does exist; substances can have different oxidation numbers. I might be wrong; but if you make an equation it's the only answer that makes logical sense.
Hopefully someone can clarify but Cl2O7 does actually exist.