Answer is: 26.67 liters of 15% acid and 13.33 liters of 33% acid are needed.
ω₁(acid) = 15% = 0,15.
ω₂(acid) = 33% = 0,33.
V₁(acid) = ?
V₂(acid) = ?
V₃(acid) = 40l.
ω₃(acid) = 21% = 0,21
1) V₁ + V₂ = 40l, V₁ = 40 - V₂.
2) 0,15·V₁ + 0,33·V₂ ÷ 40 = 0,21
0,15·(40 - V₂) + 0,33·V₂ ÷ 40 = 0,21
6 - 0,15V₂ + 0,33V₂ ÷ 40 = 0,21.
0,18V₂ = 2,4, V₂ = 13,33l.
V₁ = 40 - 13,33 = 26,67l.
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.
<u>Answer:</u> In a chemical reaction, the total mass of the particles in the system stays the same
<u>Explanation:</u>
Law of conservation of mass states that mass can neither be created nor be destroyed but it can only be transformed from one form to another form.
This also means that total mass on the reactant side must be equal to the total mass on the product side in a chemical reaction.
Every balanced chemical reaction follows law of conservation of mass.
<u>For Example:</u> Formation of water molecule
Total mass on reactant side = ![[2(2\times 1)+(2\times 16)]=36g/mol](https://tex.z-dn.net/?f=%5B2%282%5Ctimes%201%29%2B%282%5Ctimes%2016%29%5D%3D36g%2Fmol)
Total mass on product side = ![[2((2\times 1)+16)]=36g/mol](https://tex.z-dn.net/?f=%5B2%28%282%5Ctimes%201%29%2B16%29%5D%3D36g%2Fmol)
Hence, in a chemical reaction, the total mass of the particles in the system stays the same
