What are the rows of the periodic table of the elements also called?

Which of the following will have the longest-term impact on organisms in a ecosystem?

bearhunter [10]

Answer:

D. Global warming

Explanation:

Hope this Helps.

8 0

3 years ago

What is the wavelength of radiation emitted when an electron goes from the n = 7 to the n = 4 level of the Bohr hydrogen atom? G

Phantasy [73]

Answer:

the wavelength of radiation emitted is $\mathbf{\lambda= 2169.62 \ nm}$

Explanation:

The energy of the Bohr's hydrogen atom can be expressed with the formula:

$\mathtt{E_n =- \dfrac{13.6\ ev}{n^2}}$

For n = 7:

$\mathtt{E_7 =- \dfrac{13.6\ ev}{7^2}}$

$\mathtt{E_7 =-0.27755 \ eV}$

For n = 4

$\mathtt{E_4=- \dfrac{13.6\ ev}{4^2}}$

$\mathtt{E_4 =- 0.85\ eV}$

The electron goes from the n = 7 to the n = 4, then :

$\mathtt{E_7-E_4 = (-0.27755 - (-0.85) ) \ eV}$

$\mathtt{= 0.57245\ eV}$

Wavelength of the radiation emitted:

$\mathtt{\lambda= \dfrac{hc}{0.57245 \ eV}}$

where;

hc = 1242 eV.nm

$\mathtt{\lambda= \dfrac{1242 \ eV.nm }{0.57245 \ eV}}$

$\mathbf{\lambda= 2169.62 \ nm}$

4 0

3 years ago

Someone please help me and answer my question asap. i need to turn my assignment in soon... please.

Ksenya-84 [330]

Answer:

Explanation:

a. the salt produced would be Mg3N2(magnesium nitride)

b. magnesium loses 2 electron to form Mg2+ ion and nitrogen gains 3 electron to form n3-

when several of these ions come together 3 Mg2+ ion combine with 2 n3- ion to form Mg3N2 thus Mg getting six electron from nitrogen to form a ionic bond.

c. the reaction is not balanced Mg + N2 = Mg3n2

to make it balanced the reaction should be 3 Mg + N2 = Mg3N2.

the reaction was not balanced before because the number of Mg on both side of the reaction was not equal.

d. magnesium nitrate has formula Mg(NO3)2 is formed when Mg combines with nitrogen and oxygen Mg + N2 + o2

8 0

3 years ago

Which of the following decomposition reactions is/are correct?

Valentin [98]

<span>The generalized reaction for chemical decomposition is: AB → A + B

NaOH is sodium hydroxide. When sodium and water is combined it makes sodium hydroxide and hydrogen

When sodium hydroxide decomposes under thermal decomposition, it breaks down into sodium oxide and water.

Thus, </span><span>C) 2NaOH Na2O + H2O</span>

4 0

3 years ago

1 mol super cooled liquid water transformed to solid ice at -10 oC under 1 atm pressure.

Arada [10]

Answer:

Explanation:

Given that:

number of moles of super cooled liquid water = 1

Melting enthalpy of ice = 6020 J/mol

Freezing point =0 °C = (0 + 273 K)= 273 K

The decrease in entropy of the system during freezing for 1 mol (i.e during transformation from liquid water to solid ice ) = - 6020 J/mol × 1 mol /273 K = -22.051 J/K

Entropy change during further cooling from 0 °C (273 K) to -10 °C (263 K)

$\Delta \ S = \int\limits^{T_2}_{T_1}\dfrac{nC_p(s)dT}{T}$

$\Delta \ S = {nC_p(s)In \dfrac{T_2}{T_1}$

$\Delta \ S = {(1*37.7)In \dfrac{263}{273}$

Δ S = -1.4 J/K

Total entropy change of the system = - 22.05 J/K - 1.4 J/K = - 23.45 J/K

Entropy change of universe = entropy change of the system+ entropy change of the surrounding

According to the second law of thermodynamics

Entropy change of universe >0

SO,

Entropy change of the system + entropy change in the surrounding > 0

Entropy change in the surrounding > - entropy change of the system

Entropy change in the surrounding > - (- 23.53 J/K)

Entropy change in the surrounding > 23.53 J/K

b) Make some comments on entropy changes from the obtained data.

From the data obtained; we will realize that the entropy of the system decreases as cooling takes place when water is be convert to ice , randomness of these molecules reduces and as cooling proceeds , hence, entropy reduces more as well and the liberated heat will go into the surrounding due to this entropy of the surrounding increasing.

4 0

3 years ago