The human eye is a complex sensing device for visible light. The optic nerve needs a minimum of 2.0 × 10−17 J of energy to trigg
er a series of impulses that eventually reach the brain. How many photons of blue light (475 nm) are needed?
2 answers:
The number of photons needed to get the energy to trigger a series of impulses that eventually reaches the brain is: 48.7 photons
<h3><em>Further explanation</em></h3>
The photoelectric effect is an electron coming out of a metal because of electromagnetic radiation
One type of electromagnetic radiation is light
Electrons can come out of metal because they absorb electromagnetic energy radiated on metals. There is also kinetic energy released from metal, which is according to the equation:
E = hf - hfo
fo = the threshold frequency of electromagnetic waves
Radiation energy is absorbed by photons
The energy in one photon can be formulated as
Where
h = Planck's constant (6,626.10⁻³⁴ Js)
f = Frequency of electromagnetic waves
f = c / λ
c = speed of light
= 3.10⁸
λ = wavelength
Known wavelength 475 nm
475 nm = 475.10⁻⁹ m
We put it in the formula to find this light energy E = h. f
E = h. c /λ
E =: 6,626.10⁻³⁴. 3.10⁸ / 475 .10⁻⁹ m
E = 4.1.10⁻¹⁹
Because this is 1 photon energy, while the minimum energy required is 2.0 × 10⁻¹⁷ J, the number of photons needed is:
number of photons = 2.0 × 10−17 J: 4.1.10⁻¹⁹
number of photons = 48.7
<h3><em>Learn more</em></h3>Electromagnetic radiation with wavelength of 745 nm
The energy of a photon
The equation E = hf
the approximate energy of a photon
The equation for photon energy
the wavelength of a photon whose energy is twice
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The compounds can react with OH⁻ and HCO₃⁻ only C₅H₆N pyridinium
<h3><em>Further explanation </em></h3>In an acid-base reaction, it can be determined whether or not a reaction occurs by knowing the value of pKa or Ka from acid and conjugate acid (acid from the reaction)
Acids and bases according to Bronsted-Lowry
Acid = donor (donor) proton (H + ion)
Base = proton (receiver) acceptor (H + ion)
If the acid gives (H +), then the remaining acid is a conjugate base because it accepts protons. Conversely, if a base receives (H +), then the base formed can release protons and is called the conjugate acid from the original base.
From this, it can be seen whether the acid in the product can give its proton to a base (or acid which has a lower Ka value) so that the reaction can go to the right to produce the product.
The step that needs to be done is to know the pKa value of the two acids (one on the left side and one on the right side of the arrow), then just determine the value of the equilibrium constant
Can be formulated:
K acid-base reaction = Ka acid on the left : K acid on the right.
or:
pK = acid pKa on the left - pKa acid on the right
K = equilibrium constant for acid-base reactions
pK = -log K;
K value> 1 indicates the reaction can take place, or the position of equilibrium to the right.
There is some data that we need to complete from the problem above, which is the pKa value of some compounds that will react, namely:
pyridinium pKa = 5.25
acetone pKa = 19.3
butan-2-one pKa = 19
Let's look at the K value of each possible reaction:
pka H₂O = 15.74, pka of H₂CO₃ = 6.37)
- 1. C₅H₆N pyridinium
* with OH⁻
C₅H₆N + OH- ---> C₅H₅N- + H₂O
pK = pKa pyridinium - pKa H₂O
pK = 5.25 - 15.74
pK = -10.49
K values> 1 indicate the reaction can take place
* with HCO3⁻
C₅H₆N + HCO₃⁻-- ---> C₅H₅N⁻ + H₂CO₃
pK = 5.25 - 6.37
pK = -1.12
Reaction can take place
- 2. Acetone C₃H₆O
* with OH-
C₃H₆O + OH⁻ ---> C₃H₅O- + H₂O
pK = 19.3 - 15.74
pK = 3.56
Reaction does not happen
* with HCO₃-
C₃H₆O + HCO₃⁻ ----> C₃H₅O⁻ + H₂CO₃
pK = 19.3 - 6.37
pK = 12.93
Reaction does not happen
- 3. butan-2-one C₄H₇O
* with OH-
C₄H₇O + OH- ---> C₄H₆O- + H₂O
pK = 19 - 15.74
pK = 3.26
Reaction does not happen
* with HCO₃⁻
C₄H₇O + HCO₃⁻ ---> C₄H₆O⁻ + H₂CO₃
pK = 19 - 6.37
pK = 12.63
Reaction does not happen
So that can react with OH⁻ and HCO₃⁻ only C₅H₆N pyridinium
<h3><em>Learn more </em></h3>
the lowest ph
the concentrations at equilibrium.
the ph of a solution
Keywords : acid base reaction, the equilibrium constant
3.6 x 10²⁴molecules
Explanation:
Given parameters:
Mass of Na = 275g
Unknown:
Number of molecules of Na₂O =
Solution:
Since sodium is the limiting reactant, we first use it to find the number of mole of the Na₂O and transpose it into finding the number of molecules.
Given equation:
4Na + O₂ → 2Na₂O
Since the equation is balanced, let us find the number of moles of Na;
Number of moles = =
= 11.96moles
From the equation of the reaction;
4 mole of Na produced 2 moles of Na₂O
11.96 moles of Na will produce = 6moles
1 mole of a substance = 6.02 x 10²³ molecules
6 moles of Na₂O = 6 x 6.02 x 10²³ molecules = 3.6 x 10²⁴molecules
learn more:
Number of moles brainly.com/question/1841136
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