What element has an atomic number of 20 and two valence electrons in its valence shell?

Why is it useful to know the background level of extinction?

lawyer [7]

Answer:

NOAA and FWS are required by law to compare background rates to current rates.

Explanation:

5 0

3 years ago

it takes 463 kJ/mol to break an oxygen-hydrogen single bond. calculate the maximum wavelength of light for which an oxygen-hydro

Marianna [84]

Answer:

<u>2.59 × 10⁻⁷ m = 259 nm</u>

Explanation:

You need to calculate the wavelength of a photon with an energy equal to 463 kJ/mol, which is the energy to break an oxygen-hydrogen atom.

The energy of a photon and its wavelength are related by the Planck - Einstein equation:

E = hν,

Where:

E = energy of a photon,

h = Planck constant (6.626 × 10⁻³⁴ J . s) and

ν = frequency of the photon.

And:

ν = c / λ

Where:

c = speed of light (3.00 × 10⁸ m/s in vacuum)

λ = wavelength of the photon

Thus, you can derive:

E = h c / λ

Solve for λ:

λ = h c / E

Before substituting the values, convert the energy, 463 kJ/ mol, to J/bond

463 kJ/ mol × 1,000 J/kJ × 1 mol / 6.022 × 10 ²³ atom × 1 bond / atom

= 7.69×10²³ J / bond

Substitute the values and use the energy of one bond:

λ = 6.626 × 10⁻³⁴ J . s × 3.00 × 10⁸ m/s / 7.69×10²³ J = 2.59 × 10⁻⁷ m

The wavelength of light is usually shown in nanometers:

2.59 × 10⁻⁷ m × 10⁹ nm / m = 259 nm ← answer

6 0

3 years ago

A gas at 42. 0°c occupies a volume of 1. 32 l. if the volume increases to 2. 24 l, what is the new temperature in kelvin?

Nina [5.8K]

the answer is 534.54 kelvin

8 0

2 years ago

7. Who was the first explorer from France to reach North America? A. Giovanni da Verrazano C. Louis Joliet B. Jacques Cartier D.

Tanzania [10]

Jacques Cartier is the first explorer to reach North America

6 0

3 years ago

Read 2 more answers

Student conducts an experiment to determine the enthalpy of solution for lithium chloride dissolved in water. the student combin

nirvana33 [79]

Answer:- $\Delta H_s_o_l_n=-37.2\frac{kJ}{mol}$

Solution:- First of all we calculate the heat absorbed or released when the solute is added to the solvent. Here the solute is LiCl and the solvent is water.

To calculate the heat absorbed or released we use the formula:

$q=ms\Delta T$

q = heat absorbed or released

m = mass of solution

s = specific heat capacity

and $\Delta T$ = change in temperature

mass of solution = mass of solute + mass of solvent

mass of solution = 5.00 g + 100.0 g = 105.0 g

(note:- density of pure water is 1 g per mL so the mass is same as its volume)

$\Delta T$ = 33.0 - 23.0 = 10.0 degree C

s = $4.18\frac{J}{g.^0C}$

Let's plug in the values in the formula and calculate q.

q = $105.0g(4.18\frac{J}{g.^0C})(10.0^0C)$

q = 4389 J

To calculate the enthalpy of solution that is $\Delta H_s_o_l_n$ we convert q to kJ and divide by the moles of solute.

moles of solute = $5.00g(\frac{1mol}{42.39g})$

= 0.118 moles

q = $4389J(\frac{1kJ}{1000J})$ = 4.389 kJ

$\Delta H_s_o_l_n=\frac{4.389kJ}{0.118mol}$

$\Delta H_s_o_l_n$ = $37.2\frac{kJ}{mol}$

Since the heat is released which is also clear from the rise in temperature of the solution, the sign of enthapy of solution will be negative.

So, $\Delta H_s_o_l_n=-37.2\frac{kJ}{mol}$

4 0

3 years ago