Periodic table is the representation of elements in an order
The history of periodic table can be summarized as
a) 1829 : Johann Dobereiner proposed the triad rule. According to him we can classify the elements in a triad where the atomic mass of middle element is average of atomic mass of the near by two atoms.
For example : Li, Na and K is a triad. Where atomic mass of Na is average of atomic mass of K
atomic mass of Na = 7+ 39 / 2 = 23
However, with the further discovery of elements the law was rejected.
b) 1864 : John Newland proposed the law of octave. According to him we can arrange the elements in a set of seven elements where the property of second set of seven elements will resemble the properties of first of seven elements or property will be repeated after seven elements. This was also rejected due to its limited applicability.
c) Meyer : He arranged some 28 elements into six different families based on their atomic masses. The members of each familiy shared some common properties.
d) 1869 : Mendleev : He actually developed a periodic table based on atomic mass of elements. He arranged the elements into groups and periods. He even left space for some undiscovered elements, which were later on discovered.
e) 1916 : Henry Moseley : He finally arranged elements based on their atomic number based on X-ray studies. He proposed the modern periodic law that the periodic properties of elements are due to atomic number of elements.
Answer:
82.28g
Explanation:
Given parameters:
Number of moles of hydrogen gas = 7.26 moles
Unknown:
Amount of ammonia produced = ?
Solution:
We have to write the balanced equation first.
N₂ + 3H₂ → 2NH₃
Now, we work from the known to the unknown;
3 moles of H₂ will produce 2 moles of NH₃
7.26 mole of H₂ will produce
= 4.84 moles of NH₃
Molar mass of NH₃ = 14 + 3(1) = 17g/mol
Mass of NH₃ = number of moles x molar mass = 4.84 x 17 = 82.28g
The pH scale was given by Sorensen to quanitatively define strength of an acid and base
the pH scale extends from 0 to 14
For acids
The pH should be less than 7 [always]
For base
The pH should be more than 7 [always]
The pH seven is of neutral solution
pH = -log[H+]
Thus lower the pH higher the concentration of hydronium ion or protons produced by an acid
thus for the given pH scale interval [0-3] it represents strong acid [Which will give high concentration of protons on dissociation]
1.54 x 10⁶kW
Explanation:
The problem here is converting from megawatts into kilowatts.
Given 1540megawatts.
The mega- and kilo- watts are prefixes that denotes multiples of units.
1 megawatt = 10⁶watts
1 kilowatt = 10³watts
Now given 1540megawatts power to Kilowatt power;
We see that :
1000kW = 1mW
1540mW x
= 1.54 x 10⁶kW
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Answer : The volume of hydrogen gas at STP is 4550 L.
Explanation :
Combined gas law is the combination of Boyle's law, Charles's law and Gay-Lussac's law.
The combined gas equation is,

where,
= initial pressure of gas = 100.0 atm
= final pressure of gas at STP = 1 atm
= initial volume of gas = 50.0 L
= final volume of gas at STP = ?
= initial temperature of gas = 
= final temperature of gas at STP = 
Now put all the given values in the above equation, we get:


Therefore, the volume of hydrogen gas at STP is 4550 L.