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3 years ago

Explain how the periodic table is organized

Chemistry

1 answer:

igor_vitrenko [27]3 years ago

3 0

Answer:

The periodic table of elements arranges all of the known chemical elements in an informative array. Elements are arranged from left to right and top to bottom in order of increasing atomic number. Order generally coincides with increasing atomic mass. The rows are called periods.

Explanation:

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Ba(OH)2:_______.

vova2212 [387]

Answer: D

Explanation: Expand this (OH)2 you will get 2O, 2H

Hence 1Ba, 2O, 2H

5 0

3 years ago

Potassium-40 is a radioactive isotope that decays into a single argon-40 atom and other particles with a half-life of 1:25 billi

stiks02 [169]

Answer:

0.147 billion years = 147.35 million years.

Explanation:

It is known that the decay of a radioactive isotope isotope obeys first order kinetics.

Half-life time is the time needed for the reactants to be in its half concentration.

If reactant has initial concentration [A₀], after half-life time its concentration will be ([A₀]/2).

Also, it is clear that in first order decay the half-life time is independent of the initial concentration.

The half-life of Potassium-40 is 1.25 billion years.

For, first order reactions:

k = ln(2)/(t1/2) = 0.693/(t1/2).

Where, k is the rate constant of the reaction.

t1/2 is the half-life of the reaction.

∴ k =0.693/(t1/2) = 0.693/(1.25 billion years) = 0.8 billion year⁻¹.

Also, we have the integral law of first order reaction:

kt = ln([A₀]/[A]),

where, k is the rate constant of the reaction (k = 0.8 billion year⁻¹).

t is the time of the reaction (t = ??? year).

[A₀] is the initial concentration of (Potassium-40) ([A₀] = 100%).

[A] is the remaining concentration of (Potassium-40) ([A] = 88.88%).

At the time needed to be determined:

8 times as many potassium-40 atoms as argon-40 atoms. Assume the argon-40 only comes from radioactive decay.

If we start with 100% Potassium-40:

∴ The remaining concentration of Potassium-40 ([A] = 88.88%).

and that of argon-40 produced from potassium-40 decayed = 11.11%.

That the ratio of (remaining Potassium-40) to (argon-40 produced from potassium-40 decayed) is (8: 1).

∴ t = (1/k) ln([A₀]/[A]) = (1/0.8 billion year⁻¹) ln(100%/88.88%) = 0.147 billion years = 147.35 million years.

8 0

3 years ago

Given the molar absorptivity for a species X of 1600 M-1cm-1 at a wavelength of 270 nm, and 400 M-1cm-1 at a wavelength of 540 n

Andre45 [30]

Answer:

Explanation:

From the given information:

At wavelength = 270 nm

$\varepsilon x_1 = 1600 \ m^{-1} \ cm^{-1} \\ \\ \varepsilon y_1 = 200 \ m^{-1} \ cm^{-1}$

At 270 nm

Suppose x is said to be the solution for the concentration of x and y to be the solution for the concentration of y;

Then:

$\varepsilon x_1 \ l + \varepsilon y_1 \ l= 0.5 \\ \\ A = A_1 + A_2$

$1600 xl + 200 yl= 0.5$

Divide both sides by 200

$8xl + yl = \dfrac{0.5}{200}$

$8x + y = \dfrac{0.5}{200}l$

Use l = 1cm (i.e the standard length)

Then;

$8x + y = \dfrac{0.5}{200} ---- (1)$

For 540 nm:

$\varepsilon x_2 x \ l + \varepsilon y_2 y \ l= 0.5 \\ \\ 40 xl + 800 yl = 0.5$

$x + 20 y = \dfrac{0.5}{400 \ l}$

since l = 1

$x + 20 y = \dfrac{0.5}{400 \ } --- (2)$

Equating both (1) and (2) together, we have:

$8x + y - 8x - 160 y = \dfrac{0.5}{200} - \dfrac{0.5 \times 8}{400} \\ \\ \implies - 159 y = \dfrac{0.5}{200} ( 1 - \dfrac{8}{2}) \\ \\ -159 y = \dfrac{-0.5 \times 3}{200} \\ \\ 159 \ y = 0.0075 \\ \\ y = \dfrac{0.0075}{159} \\ \\ y = 0.00004716 \\ \\ y = 4.7 \times 10^{-5 } \ M$

3 0

3 years ago

Structure and correct name for 5-octyne

Leno4ka [110]

Answer:

Explanation:

(R)-5-octyne-4-ol

C8H140

5 0

4 years ago

Which of the following is a property of an ionic compound?

11111nata11111 [884]

Answer:

C. Involves a metal and a nonmetal.

Explanation:

Ionic compound involves a metal and a non-metal. Ionic compounds have electrovalent bonds between them.

These compounds are usually made up of metals and non - metals combining to form a unit.

The metals usually has low electronegativity and transfers it electrons to the non - metal.
The non-metal has high affinity for the electron.
The electrostatic attraction between the ions formed results in the ionic bond.

6 0

3 years ago