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3 years ago

What is the kinetic energy of the emitted electrons when cesium is exposed to UV rays of frequency 1.0×1015Hz?

1 answer:

3 0

In order to emit electrons, the cesium will have to absorb photons. Each photon will knock out one electron by transferring its energy to the electron. Therefore, by the principle of energy conservation, the energy of the removed electron will be equal to the energy of the incident photon. That energy is calculated using Planck's equation:

E = hf

E = 6.63 x 10⁻³⁴ * 1 x 10¹⁵
E = 6.63 x 10⁻¹⁹ Joules

The electron will have 6.63 x 10⁻¹⁹ Joules of kinetic energy

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What mass of CO is needed to react completely with55.0 g of Fe2O3(s)+CO(g) yield Fe(s)+CO2(g)?

Katarina [22]

Answer:

28.9 g

Explanation:

We know that we will need a balanced equation with masses, moles, and molar masses of the compounds involved.

<em>Gather all the information in one place</em> with molar masses above the formulas and masses below them.

$M_{r}$ : 159.69 28.01

Fe₂O₃ + 3CO ⟶ 2Fe + 3CO₂

Mass/g: 55.0

1. Use the molar mass of Fe₂O₃ to calculate the moles of Fe₂O₃.

$\text{Moles of Fe$_{2}$O$_{3}$} =\text{55.0 g Fe$_{2}$O$_{3}$} \times \frac{\text{1 mol Fe$_{2}$O$_{3}$}}{\text{159.69 g Fe$_{2}$O$_{3}$}}= \text{0.3444 mol Fe$_{2}$O$_{3}$}$

2. Use the molar ratio of CO:Fe₂O₃ to calculate the moles of CO.

$\text{Moles of CO} = \text{0.3444 mol Fe$_{2}$O$_{3}$} \times \frac{\text{3 mol CO}}{\text{1 mol Fe$_{2}$O$_{3}$}}= \text{1.033 mol CO}$

3.Use the molar mass of CO to calculate the mass of CO.

$\text{Mass of CO} = \text{1.033 mol CO} \times \frac{\text{28.01 g CO} }{\text{1 mol CO}}= \textbf{28.9 g CO}$

3 0

3 years ago

Read 2 more answers

Aliyah marks a line on her driveway with a piece of chalk and another line 50ft away Then she stands with both feet at the line

Mariulka [41]

Answer:

Speed

Explanation:

Aliyah must have been trying to find her speed.

The speed is a measure of how fast an object or a body is and it is calculated by finding the ratio of distance with time. Mathematically,

speed = $\frac{distance}{time}$ with a unit of m/s.

<em>Hence, with the distance measured on the ground and Aliyah trying to find the time it will take her to cover the distance while running, she must have been trying to find how fast she can run, that is, speed. </em>

3 0

3 years ago

A 237g sample of molybdnum metal is heated to 100.1 0C and then dropped into an insulated cup containing 244 g of water at 10.0

miv72 [106K]

Answer:

The specific heat of molybdenum is 0.254 joules per gram-Celsius.

Explanation:

We consider the system formed by the molybdenum metal and water as our system, a control mass inside an insulated cup, that is, a container that avoids any energy and mass interactions between system and surroundings.

From statement we notice that metal is cooled down whereas water is heated. According to the First Law of Thermodynamics, we know that:

$Q_{metal} - Q_{water} = 0$

$Q_{metal} = Q_{water}$

Where:

$Q_{water}$ - Heat received by water, measured in joules.

$Q_{metal}$ - Heat released by metal, measured in joules.

Now we expand this identity by definition of sensible heat:

$m_{metal}\cdot c_{metal}\cdot (T_{m,o}-T) = m_{water}\cdot c_{water}\cdot (T-T_{w,o})$

The specific heat of the metal is cleared within equation above:

$c_{metal} = \frac{m_{water}\cdot c_{water}\cdot (T-T_{w,o})}{m_{metal}\cdot (T_{m,o}-T)}$

If we know that $m_{water} = 0.237\,kg$ , $m_{metal} = 0.244\,kg$ , $c_{water} = 4186\,\frac{J}{kg\cdot ^{\circ}C}$ , $T_{w,o} = 10\,^{\circ}C$ , $T_{m,o} = 100.10\,^{\circ}C$ and $T = 15.30\,^{\circ}C$ , the specific heat of molybdenum is:

$c_{metal} = \frac{(0.237\,kg)\cdot \left(4186\,\frac{J}{kg\cdot ^{\circ}C} \right)\cdot (15.30\,^{\circ}C-10\,^{\circ}C)}{(0.244\,kg)\cdot (100.10\,^{\circ}C-15.30\,^{\circ}C)}$

$c_{metal} = 254.119\,\frac{J}{kg\cdot ^{\circ}C}$

The specific heat of molybdenum is 0.254 joules per gram-Celsius.

5 0

3 years ago

AlCl3 + Na NaCl + Al Did Cl change oxidation number?

gizmo_the_mogwai [7]

Yes. If this is the balanced equation:

AlCl3 + 3Na —— 3NaCl + Al

then Al was reduced from a 3+ oxidation (to neutralize the 3- from the chlorine) to a 0 oxidation (elemental ground state).

6 0

3 years ago

Read 2 more answers

Read the information about the halogen family.

Elodia [21]

Answer:

See explanation

Explanation:

Chlorine is a member of the halogen family known as a toxic yellowish green gas. Inhalation of chlorine for a prolonged period of time leads to pulmonary edema. If a person comes in contact with compressed liquid chlorine the person may experience frostbite of the skin and eyes.

However chlorine is very useful in water disinfection and is preferred in water treatment because it provides residual disinfection of the treated water.

Chlorine gas may be dissolved in NaOH to form oxochlorate I which is used as a bleach in cleaning.

7 0

3 years ago