All categories

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

You might be interested in

A tank contains 200 gallons of water in which 300 grams of salt is dissolved. A brine solution containing 0.4 kilograms of salt

Nadusha1986 [10]

Answer:

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

Explanation:

given amount of salt at time t is A(t)

initial amount of salt =300 gm =0.3kg

=>A(0)=0.3

rate of salt inflow =5*0.4= 2 kg/min

rate of salt out flow =5*A/(200)=A/40

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>

6 0

3 years ago

Negatively charged particles within the atom are called what?

Ivahew [28]

Negatively charged particles in atom - Electrons

5 0

3 years ago

Which of the following are diatomic elements? Select all that apply.

TiliK225 [7]

Answer:

Explanation:

A diatomic element in that list is Bromine

8 0

3 years ago

4. Chlorine exists in two forms - chlorine-35 and

White raven [17]

Answer: sorry i dont knowExplanation:

5 0

3 years ago

What is an example of conduction

Alexandra [31]

Explanation:When the stove turns on the skillet will become very hot because of the conduction of heat transferring from the stove to the skillet.

7 0

3 years ago