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3 years ago

Please Help!!!!!!!!

Chemistry

2 answers:

Alex3 years ago

8 0

Answer: very low amount of humus :)

Explanation:

Ira Lisetskai [31]3 years ago

7 0

Well I think it’s B but I hope I’m not wrong

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To calculate the frequency of an electromagnetic wave, you need to know the speed of the wave which you already know as 186000 m

nirvana33 [79]

To finish calculating the frequency of an electromagnetic wave, you need the wavelength

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3 years ago

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What is a non-example of an electrical conductor?

goblinko [34]

Answer: Sulphur, Phosphorus, Wood are non-conductors of electricity due to no presence of free electrons in outermost shell.

Explanation:

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2 years ago

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The rate constant k for a certain reaction is measured at two different temperatures temperature 376.0 °c 4.8 x 108 280.0 °C 2.3

9966 [12]

Answer:

The activation energy for this reaction = 23 kJ/mol.

Explanation:

Using the expression,

$\ln \dfrac{k_{1}}{k_{2}} =-\dfrac{E_{a}}{R} \left (\dfrac{1}{T_1}-\dfrac{1}{T_2} \right )$

Where,

$k_1\ is\ the\ rate\ constant\ at\ T_1$

$k_2\ is\ the\ rate\ constant\ at\ T_2$

$E_a$ is the activation energy

R is Gas constant having value = 8.314×10⁻³ kJ / K mol

$k_2=2.3\times 10^8$

$T_2=280\ ^0C$

The conversion of T( °C) to T(K) is shown below:

T(K) = T( °C) + 273.15

So,

T = (280 + 273.15) K = 553.15 K

$T_2=553.15\ K$

$k_1=4.8\times 10^8$

$T_1=376\ ^0C$

The conversion of T( °C) to T(K) is shown below:

T(K) = T( °C) + 273.15

So,

T = (376 + 273.15) K = 649.15 K

$T_1=649.15\ K$

So,

$\left(\ln \left(\:\frac{4.8\times \:\:\:10^8}{2.3\times \:\:\:10^8}\right)\right)\:=-\frac{E_a}{8.314\times \:10^{-3}\ kJ/mol.K}\times \:\left(\frac{1}{649.15\ K}-\frac{1}{553.15\ K}\right)$

$E_a=-\frac{10^{-3}\times \:8.314\ln \left(\frac{10^8\times \:4.8}{10^8\times \:2.3}\right)}{-\frac{96}{359077.3225}}\ kJ/mol$

$E_a=-\frac{\frac{8.314\ln \left(\frac{4.8}{2.3}\right)}{1000}}{-\frac{96}{359077.3225}}\ kJ/mol$

$E_a=22.87\ kJ/mol$

<u>The activation energy for this reaction = 23 kJ/mol.</u>

6 0

3 years ago

What is the difference between physical and chemical properties? Give 3 examples of each.

IceJOKER [234]

Explanation:

1.A physical property is an aspect of matter that can be seen or measured without changing its chemical composition. Examples of physical properties include color, molecular weight, and volume.

A chemical property is observed only by changing the chemical identity of a substance. In other words, the only way to detect a chemical is to perform a chemical reaction.

2.This property measures the ability of chemical change. Examples of chemical properties are reactivity, flammability, and oxidation state.

The physical properties of a substance do not involve any chemical reaction. These include density, color, mass, hardness, freezing points, electrical properties, and the like.

Chemical properties include the reaction of chemicals with other substances. These reactions lead to the disappearance of the raw material and the appearance of new materials that have different physical and chemical properties.

3.Chemical properties can be compared to physical properties; On the contrary, they are recognizable without changing the structure of matter. However, for many properties in the field of physical chemistry and other disciplines at the boundary between chemistry and physics, the distinction can be a matter for the researcher's point of view. The properties of materials, both physical and chemical, can be seen as metaphysical; This means that it is secondary to the principle of tangible reality. Multiple metamorphic layers are also possible.

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3 years ago

. percent iron in a mixture that is 52.2% Fe2O3

AVprozaik [17]

Answer:

36.51%.

Explanation:

First find the percentage of iron in pure Fe2O3 using the atomic masses of the elements:

= (2 * 55.845) * 100 / (2*55.845+ 3*15.999)

= 69.94 %.

So the percentage of iron in the mixture

= 52.2 * 0.6994

= 36.51 (answer).

8 0

3 years ago