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Nana76 [90]
3 years ago
11

For a given fluorophore, select the choice that correctly lists the processes of fluorescence, absorption, and phosphorescence i

n order from shortest to longest wavelength.
a. absorption, fluorescence, phosphorescence
b. Fluorescence = phosphorescence, absorption
c. fluorescence, phosphorescence, absorption
d. phosphorescence, fluorescence, absorption
e. absorption, phosphorescence, fluorescence
f. absorption, fluorescence = phosphorescence
Chemistry
1 answer:
xxTIMURxx [149]3 years ago
3 0

Answer:

absorption, fluorescence = phosphorescence

Explanation:

Given a particular fluorophore, the wavelength of absorption of the fluorophore is always shorter. Both fluorescence and phosphorescence are kinds of photoluminescence.

Recall that both fluorescence and phosphorescence occur at a longer wavelength. The difference between the two is only in the time taken during the process. While fluorescence takes a shorter time to occur, phosphorescence takes a longer time to occur.

The major difference between fluorescence and phosphorescence is that change of spin occurs during phosphorescence but not fluorescence.

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Need help asap with this chemistry if someone could help me
Burka [1]

Answer:

<h3>1)</h3>

Structure One:

  • N: -2
  • C: 0
  • O: +1

Structure Two:

  • N: 0
  • C: 0
  • O: -1

Structure Three:

  • N: -1
  • C: 0
  • O: 0.

Structure Number Two would likely be the most stable structure.

<h3>2)</h3>
  • All five C atoms: 0
  • All six H atoms to C: 0
  • N atom: +1.

The N atom is the one that is "likely" to be attracted to an anion. See explanation.

Explanation:

When calculating the formal charge for an atom, the assumption is that electrons in a chemical bond are shared equally between the two bonding atoms. The formula for the formal charge of an atom can be written as:

\text{Formal Charge} \\ = \text{Number of Valence Electrons in Element} \\ \phantom{=}-\text{Number of Chemical Bonds} \\\phantom{=} - \text{Number of nonbonding Lone Pair Electrons}.

For example, for the N atom in structure one of the first question,

  • N is in IUPAC group 15. There are 15 - 10 = 5 valence electrons on N.
  • This N atom is connected to only 1 chemical bond.
  • There are three pairs, or 6 electrons that aren't in a chemical bond.

The formal charge of this N atom will be 5 - 1 - 6 = -2.

Apply this rule to the other atoms. Note that a double bond counts as two bonds while a triple bond counts as three.

<h3>1)</h3>

Structure One:

  • N: -2
  • C: 0
  • O: +1

Structure Two:

  • N: 0
  • C: 0
  • O: -1

Structure Three:

  • N: -1
  • C: 0
  • O: 0.

In general, the formal charge on all atoms in a molecule or an ion shall be as close to zero as possible. That rules out Structure number one.

Additionally, if there is a negative charge on one of the atoms, that atom shall preferably be the most electronegative one in the entire molecule. O is more electronegative than N. Structure two will likely be favored over structure three.

<h3>2)</h3>

Similarly,

  • All five C atoms: 0
  • All six H atoms to C: 0
  • N atom: +1.

Assuming that electrons in a chemical bond are shared equally (which is likely not the case,) the nitrogen atom in this molecule will carry a positive charge. By that assumption, it would attract an anion.

Note that in reality this assumption seldom holds. In this ion, the N-H bond is highly polarized such that the partial positive charge is mostly located on the H atom bonded to the N atom. This example shows how the formal charge assumption might give misleading information. However, for the sake of this particular problem, the N atom is the one that is "likely" to be attracted to an anion.

5 0
3 years ago
Use the molar solubility 3.27×10−11m in pure water to calculate ksp for nis.
Ne4ueva [31]

Answer:

Ksp = 1.07x10⁻²¹

Explanation:

Molar solubility is defined as moles of solute can be dissolved in 1L.

Ksp for NiS is defined as:

NiS(s) ⇄ Ni²⁺(aq) + S²⁻(aq)

Ksp = [Ni²⁺] [S²⁻]

As molar solubility is 3.27x10⁻¹¹M, concentration of [Ni²⁺] and [S²⁻] is 3.27x10⁻¹¹M for both.

Replacing:

Ksp = [3.27x10⁻¹¹M] [3.27x10⁻¹¹M]

<em>Ksp = 1.07x10⁻²¹</em>

<em></em>

4 0
3 years ago
Which substances in the diagram are most unstable? positive values of enthalpy negative values of enthalpy negative values -50 t
NemiM [27]

Answer:

no  s e

Explanation:

tampocose

8 0
3 years ago
Read 2 more answers
Un móvil se mueve con movimiento acelerado. En los segundo 2 y 3 los espacios recorridos son 90 y 120 m, Calcula la velocidad in
faust18 [17]

Answer:

La velocidad inicial es 55 \frac{m}{s}y su aceleración es -10 \frac{m}{s^{2} }

Explanation:

Un movimiento es rectilíneo uniformemente variado, cuando la trayectoria del móvil es una línea recta y su velocidad  varia la misma cantidad en cada unidad de tiempo . Dicho de otra manera, este movimiento se caracteriza por una trayectoria que es una línea recta y la velocidad cambia su módulo de manera uniforme: aumenta o disminuye en la misma cantidad por cada unidad de tiempo. Y la aceleración es constante y no nula (diferente de cero).

En este caso la posición del objeto esta dada por la expresión:

x=x0+v0*t+\frac{1}{2} *a*t^{2}

donde x es la posición del cuerpo en un instante dado, x0 la posición en el instante inicial, v0 la velocidad inicial y a la aceleración.

En este caso, por un lado podes considerar:

  • x= 90 m
  • x0= 0 m
  • v0= ?
  • t= 2
  • a= ?

Reemplazando obtenes:

90=v0*2+\frac{1}{2} *a*2^{2}

90=v0*2+\frac{1}{2} *a*4

90=v0*2+2*a

Y por otro lado tenes:

  • x= 120 m
  • x0= 0
  • v0= ?
  • t= 3
  • a= ?

Reemplazando obtenes:

120=v0*3+\frac{1}{2} *a*3^{2}

120=v0*3+\frac{1}{2} *a*9

120=v0*3+\frac{9}{2} *a

Por lo que tenes el siguiente sistema de ecuaciones:

\left \{ {{2*v0+2*a=90} \atop {3*v0+\frac{9}{2} *a=120}} \right.

Resolviendo por el método de sustitución, que consiste en aislar en una ecuación una de las dos incógnitas para sustituirla en la otra ecuación, obtenes:

Despejando v0 de la primera ecuación:

v0= \frac{90-2*a}{2}

Reemplazando en la segunda ecuación:

120=\frac{90-2*a}{2} *3+\frac{9}{2} *a

Resolviendo:

120=(90-2*a)*\frac{3}{2} +\frac{9}{2} *a

120=135-3*a +\frac{9}{2} *a

120-135=-3*a +\frac{9}{2} *a

-15=\frac{3}{2} *a

\frac{-15}{\frac{3}{2} } =a

-10=a

Reemplazando el valor de a en la expresión despejada anteriormente obtenes:

v0= \frac{90-2*(-10)}{2}

Resolviendo:

v0= \frac{90+20}{2}

v0= \frac{110}{2}

v0=55

<u><em>La velocidad inicial es 55 </em></u>\frac{m}{s}<u><em>y su aceleración es -10 </em></u>\frac{m}{s^{2} }<u><em></em></u>

3 0
3 years ago
A scientist is combining two gray elements. He thinks he will get a gray compounds. Use what you learned in this lesson to expla
adelina 88 [10]

Answer:

Explanation:

Depending on the elements that are being combined, a chemical reaction could occur and cause a change of color to take place if the elements reacts to the other one.

3 0
2 years ago
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