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3 years ago

Quis critérios foram usadps por dobereiner em sua tentava de organiza os elementos químicos?

Chemistry

1 answer:

anyanavicka [17]3 years ago

8 0

Döbereiner grouped the known elements into <em>triads</em> (sets of three) so that

• The <em>atomic mass of the middle element</em> was approximately the average of the other two

• The <em>chemical properties of the middle element</em> were between those of the other two

• The <em>physical properties of the middle element</em> were between those of the other two

One example of a triad is Li – Na – K.

(a) Atomic mass of Na = 23.0 u

Average atomic mass of Li and K = (6.9 u + 39.1 u)/2 = 46.0 u/2 = 23.0 u

(b) Li reacts slowly with water. Na reacts rapidly. Potassium reacts violently.

Average melting point of Li and K = (454 °C + 330 °C)/2 = 784 °C/2

= 392 °C

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Answer:

<h3>Therefore, after long period of time 80kg of salt will remain in tank</h3>

Explanation:

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=>A(0)=0.3

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rate of change of salt at time t , dA/dt= rate of salt inflow- ratew of salt outflow

$dA/dt=2-(A/40)\\\\dA=2dt-(A/40)dt\\\\dA+(A/40)dt=2dt$

integrating factor

$=e^{\int\limits (1/40) \, dt}$

integrating factor $=e^{(1/40)t}$

multiply on both sides by $=e^{(1/40)t}$

$dAe^{(1/40)t}+(A/40)e^{(1/40)t} dt =2e^{(1/40)t}t\\\\(Ae^{(1/40)t})=2e^{(1/40)t}t$

integrate on both sides

$\int\limits(Ae^{(1/40)t})=\int\limits2e^{(1/40)t}dt\\\\(Ae^{(1/40)t})=2*40e^{(1/40)t}+C\\\\A=80+(C/e^{(1/40)t})\\\\A(0)=0.3\\\\0.3=80+(C/e^{(1/40)t}^*^0)\\\\0.3=80+(C/1)\\\\C=0.3-80\\\\C=-79.7\\\\A(t)=80-(79.7/e^{(1/40)t})$

after long period of time means t - > ∞

${t \to \infty}\\\\ \lim_{t \to \infty} A_t \\\\ \lim_{t \to \infty} (80)-(79/{e^{(1/40)t}}\\\\=80-(0)\\\\=80$

<h3>Therefore, after long period of time 80kg of salt will remain in tank</h3>

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