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Which is the electron configuration for boron?

Alexxx [7]

Boron:atomic number-5,valency-+3,atomic mass- 11amu

3 0

3 years ago

A solution containing 20.0 g of an unknown liquid and 110.0 g water has a freezing point of .32 °C. Given Kf 1.86°C/m for water,

hjlf

Answer:

A. 256

Explanation:

In a solution where a liquid is the sovent, we'll use the van't Hoff factor, which is the ratio between the number of moles of particles produced in solution and the number of moles of solute dissolved, will be equal to 1.

ΔTemp.f = i * Kf * b

where,

ΔTemp.f = the freezing-point depression;

i = the van't Hoff factor

Kf = the cryoscopic constant of the solvent;

b = the molality of the solution.

So the freezing-point depression by definition is the difference between the the freezing point of the pure solvent and the freesing point of the solution.

Mathematically,

ΔTemp.f = Temp.f° - Temp.f

where,

Temp.f° = the freezing point of the pure solvent.

Temp.f = the freezin point of the solution.

Freezing point of pure water = 0°C

ΔTemp.f = 0 - (-1.32)

= 1.32°C

i = 1,

Kf = 1.86 °Ckg/mol

Solving for the molality, b = ΔTemp.f/( i * Kf)

= 1.32/(1*1.86)

= 0.71 mol/kg

Converting from mol/kg to mol/g,

0.71 mol/kg * 1kg/1000g

= 0.00071 mol/g.

Mass of solvent = 110g

Number of moles = mass * molality

= 0.00071 * 110

= 0.078 mol.

To calculate molar mass,

Molar mass (g/mol) = mass/number of moles

Mass of solute (liquid) = 20g

Molar mass = 20/0.078

= 256.2 g/mol

4 0

3 years ago

Define or explain the following terms. a) Equilibrium constant expression - b) Equilibrium constant - c) Absorbance - d) Beer's

tankabanditka [31]

Explanation:

(a) Equilibrium constant expression is ratio of concentrations of products over reactants each raised to their power of stoichiometric coefficients.

For example consider an equilibrium which is:

$aA+bB\rightleftharpoons cC+dD$

The expression is:

$K_c=\frac {[C]^c[D]^d}{[A]^a[B]^b}$

(b) Equilibrium constant of the chemical reaction is value of the reaction quotient of the reaction at the stage of chemical equilibrium which is a state that is approached by the dynamic chemical system at which the composition of the reactant and the product has no measurable tendency towards the change.

(c) Absorbance is the measure of capacity of the substance to absorb the light of a specific wavelength. Absorbance is equal to the logarithm of reciprocal of transmittance.

(d) The Beer's law relates attenuation of the light to properties of material through which light is travelling.

The expression for the law is:

A = ε × l× c

Where,

A is the absorbance

ε is molar absorptivity coefficient

l is the path length

c is the concentration.

3 0

3 years ago

And active alkaline earth Metal with 56 protons

snow_tiger [21]

Protons can't change in stable elements so its means that is Barium

4 0

3 years ago

Which statement describes a process involved in the evolution of Earth’s early atmosphere?

morpeh [17]

Answer:

D

Explanation:

5 0

3 years ago

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