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Elza [17]
3 years ago
12

In compliance with conservation of energy, Einstein explained that in the photoelectric effect, the energy of a photon (hv) abso

rbed by a metal is the sum of the work function (Φ), the minimum energy needed to dislodge an electron from the metal’s surface, and the kinetic energy (Ek) of the electron: hv = Φ + Ek. When light of wavelength 358.1 nm falls on the surface of potassium metal, the speed (u) of the dislodged electron is 6.40 x 10⁵ m7s. (a) What is Ek (½mu²) of the dislodged electron? (b) What is Φ (in J) of potassium?
Chemistry
1 answer:
3241004551 [841]3 years ago
7 0

Answer:

 a) 1.866 × 10 ⁻¹⁹ J      b)   3.685 × 10⁻¹⁹ J

Explanation:

the constants involved are

h ( Planck constant) = 6.626 × 10⁻³⁴ m² kg/s

Me of electron = 9.109 × 10 ⁻³¹ kg

speed of light = 3.0 × 10 ⁸ m/s

a) the Ek ( kinetic energy of the dislodged electron) = 0.5 mu²

Ek = 0.5 × 9.109 × 10⁻³¹ × ( 6.40 × 10⁵ )² = 1.866 × 10 ⁻¹⁹ J

b) Φ ( minimum energy needed to dislodge the electron ) can be calculated by this formula

hv =   Φ + Ek

where Ek = 1.866 × 10 ⁻¹⁹ J

v ( threshold frequency ) = c / λ where c is the speed of light and λ is the wavelength of light = 358.1 nm = 3.581 × 10⁻⁷ m

v = ( 3.0 × 10 ⁸ m/s ) / (3.581 × 10⁻⁷ m ) = 8.378 × 10¹⁴ s⁻¹

hv = 6.626 × 10⁻³⁴ m² kg/s ×  8.378 × 10¹⁴ s⁻¹ = 5.551 × 10⁻¹⁹ J

5.551 × 10⁻¹⁹ J = 1.866 × 10 ⁻¹⁹ J + Φ

Φ = 5.551 × 10⁻¹⁹ J - 1.866 × 10 ⁻¹⁹ J = 3.685 × 10⁻¹⁹ J

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krek1111 [17]
To solve the problem, we assume the sample to be ideal. Then, we use the ideal gas equation which is expressed as PV = nRT. From the first condition of the nitrogen gas sample, we calculate the number of moles.

n = PV / RT
n = (98.7x 10^3 Pa x 0.01 m^3) / (8.314 Pa m^3/ mol K) x 298.15 K
n = 0.40 mol N2

At the second condition, the number of moles stays the same however pressure and temperature was changed. So, the new volume is calculated as follows:

V = nRT / P
V = 0.40 x 8.314 x 293.15 / 102.7 x 10^3
V = 9.49 x 10^-3 m^3 or 9.49 L
7 0
3 years ago
When 125 grams of FeO react with 25.0 grams of Al, how many grams of Fe can be produced? FeO + Al → Fe + Al2O3 25.9 g Fe 38.7 g
Serga [27]

<u>Answer:</u> The mass of iron produced will be 77.6 grams

<u>Explanation:</u>

To calculate the number of moles, we use the equation:

\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}     .....(1)

  • <u>For FeO:</u>

Given mass of FeO = 125 g

Molar mass of FeO = 71.8 g/mol

Putting values in equation 1, we get:

\text{Moles of FeO}=\frac{125g}{71.8g/mol}=1.74mol

  • <u>For aluminium:</u>

Given mass of aluminium = 25.0 g

Molar mass of aluminium = 27 g/mol

Putting values in equation 1, we get:

\text{Moles of aluminium}=\frac{25.0g}{27g/mol}=0.93mol

The given chemical reaction follows:

3FeO+2Al\rightarrow 3Fe+Al_2O_3

By Stoichiometry of the reaction:

2 moles of aluminium metal reacts with 3 mole of FeO

So, 0.93 moles of aluminium metal will react with = \frac{3}{2}\times 0.93=1.395mol of FeO

As, given amount of FeO is more than the required amount. So, it is considered as an excess reagent.

Thus, aluminium metal is considered as a limiting reagent because it limits the formation of product.

By Stoichiometry of the reaction:

2 moles of aluminium metal produces 3 mole of iron metal

So, 0.93 moles of aluminium metal will produce = \frac{3}{2}\times 0.93=1.395moles of iron metal

  • Now, calculating the mass of iron metal from equation 1, we get:

Molar mass of iron = 55.85 g/mol

Moles of iron = 1.395 moles

Putting values in equation 1, we get:

1.395mol=\frac{\text{Mass of iron}}{55.85g/mol}\\\\\text{Mass of iron}=(1.395mol\times 55.85g/mol)=77.6g

Hence, the mass of iron produced will be 77.6 grams

4 0
3 years ago
Which of the following is used for chemical symbols today? a. drawings c. letters b. icons d. numbers
devlian [24]

Answer:

Letters

Explanation:

For example, today we use the periodic table which is full of elements named with 1 or 2 letters. Like how Helium is He and Sodium is Na. Hope this helps!!!

3 0
3 years ago
A machine has a mechanical advantage of 0.6. What force should be applied to the machine to make it apply 600 N to an object?
Vinil7 [7]

Answer:

1000N is needed to be applied.

Explanation:

Machines make doing work easier. They allow us use small effort to carry out work on huge amount of load.

The mechanical advantage of a machine;

(M.A) =load/effort

M.A = 0.6

Load =600N

effort =?

0.6 = 600/effort

effort = 600/0.6

effort = 1000N

8 0
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Anatom that has lewer neutrons than protons and more electrons than protons is
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Answer:

a negative ion, and an isotope.

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