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abruzzese [7]
3 years ago
12

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.

(c) Melting point of Na = 371 °C.

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

       = 392 °C

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The drawing shows two long rod shaped Structures with horizontal light dark bands
7nadin3 [17]

Answer:

From my side I think it is Photoreceptors cells :

A photoreceptor cell is a specialized type of neuroepithelial cell found in the retina that is capable of visual phototransduction. The great biological importance of photoreceptors is that they convert light (visible electromagnetic radiation) into signals that can stimulate biological processes. To be more specific, photoreceptor proteins in the cell absorb photons, triggering a change in the cell's membrane potential.

There are currently three known types of photoreceptor cells in mammalian eyes: rods, cones, and photosensitive retinal ganglion cells. The two classic photoreceptor cells are rods and cones, each contributing information used by the visual system to form a representation of the visual world, sight. The rods are narrower than the cones and distributed differently across the retina, but the chemical process in each that supports phototransduction is similar. A third class of mammalian photoreceptor cell was discovered during the 1990s: the photosensitive ganglion cells. These cells do not contribute to sight directly, but are thought to support circadian rhythms and pupillary reflex.

Explanation:

4 0
3 years ago
Translate the skeleton chemical equation:
Minchanka [31]

Answer:

MgBr₂ + AgNO₃ => Mg(NO₃)₂ + AgBr

Explanation:

Find the element symbol and charge of each element on the periodic table. For polyatomic ions (nitrate), reference your polyatomic ions chart. Use the "partner's charge" rule to find the number of atoms in each compound.

Charges are written as superscripts. "1" is usually not written, just the + or - sign. The charge of silver is 1, which is the (I) bracket roman numeral 1. It is indicated like that because it is multivalent, meaning it has more than one possible charge.

<u>Write each element as an ion</u> (with the charge).

Magnesium is Mg²⁺

Bromide is Br⁻

Silver(I) is Ag⁺

Nitrate is (NO₃)⁻

<u>Write each compound.</u>

REACTANTS SIDE

Magnesium bromide

Mg²⁺Br⁻    Cross over the partner's charge. Since Br is charge 1, Mg has 1 atom. Since Mg has charge 2, Br has 2 atoms.

MgBr₂

Silver(I) nitrate

Ag⁺(NO₃)⁻

AgNO₃       Both have 1 atom because each partner's charge was 1. You do not need to write brackets if nitrate only has 1 atom.

PRODUCTS SIDE

Magnesium nitrate

Mg²⁺(NO₃)⁻

Mg(NO₃)₂      Nitrate has 2 atoms because magnesium's charge is 2.

Silver(I) bromide

Ag⁺Br⁻

AgBr       Both have 1 atom.

Write the compounds into an equation. Reactants go on the left side, products go on the right side. Between the reactants and products, write an arrow.

MgBr₂ + AgNO₃ => Mg(NO₃)₂ + AgBr

6 0
4 years ago
For NH4+, write an equation that shows how the cation acts as an acid
vazorg [7]

According to  Bronsted-Lowry theory acid are donor of protons and bases are acceptors of protons (the hydrogen cation or H⁺).

1) NH₄⁺(aq) + H₂O(l) ⇄ NH₃ + H₃O⁺(aq); the ammonium cation (NH₄⁺) gives proton to water.

2)  [Co(H₂O)₆]³⁺ + H₂O ⇌ [Co(H₂O)₅(OH)]²⁺ + H₃O⁺; cobalt cation (Co³⁺) forms complex cation with six molecules of water, which act like acid and gives protons.

3) CH₂NH₃⁺(aq) + H₂O(l) ⇄ CH₂NH₂ + H₃O⁺(aq); H⁺ is cationic form of atomic hydrogen, the hydrated form of the hydrogen cation is the hydronium ion H₃O⁺(aq).

6 0
4 years ago
Read 2 more answers
Carbon dioxide dissolves in water to form carbonic acid, which is primarily dissolved CO2. Dissolved CO2 satisfies the equilibri
lorasvet [3.4K]

Explanation:

The reaction equation will be as follows.

           CO_{2}(aq) + H_{2}O \rightleftharpoons H^{+}(aq) + HCO^{-}_{3}(aq)

Calculate the amount of CO_{2} dissolved as follows.

             CO_{2}(aq) = K_{CO_{2}} \times P_{CO_{2}}

It is given that K_{CO_{2}} = 0.032 M/atm and P_{CO_{2}} = 1.9 \times 10^{-4} atm.

Hence, [CO_{2}] will be calculated as follows.

           [CO_{2}] = K_{CO_{2}} \times P_{CO_{2}}          

                           = 0.032 M/atm \times 1.9 \times 10^{-4}atm

                           = 0.0608 \times 10^{-4}

or,                        = 0.608 \times 10^{-5}

It is given that K_{a} = 4.46 \times 10^{-7}

As,      K_{a} = \frac{[H^{+}]^{2}}{[CO_{2}]}

          4.46 \times 10^{-7} = \frac{[H^{+}]^{2}}{0.608 \times 10^{-5}}  

               [H^{+}]^{2} = 2.71 \times 10^{-12}

                      [H^{+}] = 1.64 \times 10^{-6}

Since, we know that pH = -log [H^{+}]

So,                      pH = -log (1.64 \times 10^{-6})

                                 = 5.7

Therefore, we can conclude that pH of water in equilibrium with the atmosphere is 5.7.

3 0
3 years ago
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