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AveGali [126]
3 years ago
5

Select all the correct answers.

Chemistry
2 answers:
swat323 years ago
8 0

Silver tarnishes and becomes black when exposed to oxygen:

              Diesel fuel burns when it is heated:

Mashutka [201]3 years ago
7 0

Answer:

              Silver tarnishes and becomes black when exposed to oxygen:

              Diesel fuel burns when it is heated:

Explanation:

                    Chemical Changes are those changes in which the chemistry at molecular level is changed as the starting material is converted in to a new and different final material. This change takes place with the breaking of old bonds and forming of new bonds respectively.

Silver tarnishes and becomes black when exposed to oxygen:

This is a chemical change as Silver a white and lustrous starting material is being converted into a tarnish black final material. However, Silver doesn't readily react with oxygen at normal conditions. It readily react with Sulfur containing compounds in air and produces black compound as Ag₂S.

Diesel fuel burns when it is heated:

Diesel is a mixture of hydrocarbons ranging approximately from C₁₀H₂₀ to C₁₅H₂₈. When these hydrocarbons are burnt they produces a new materials i.e. CO₂ and H₂O.

                             C₁₀H₂₀  +  15 O₂    →     10 CO₂  + 10 H₂O

Hence, it is also a chemical reaction.

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Rhodium crystallizes in a face-centered cubic unit cell. The radius of a rhodium atom is 135 pm. Determine the density of rhodiu
Deffense [45]

Answer:

Density of unit cell ( rhodium) = 12.279 g/cm³

Explanation:

Given that:

The radius (r) of a rhodium atom = 135 pm

The atomic mass of rhodium = 102.90 amu

For a face-centered cubic unit cell,

r = \dfrac{a}{2\sqrt{2}}

where;

a = edge length.

Making "a" the subject of the formula:

a = 2 \sqrt{2} \times r

a = 2 \times 1.414 \times 135 \ pm

a = 381.8 pm

to cm, we get:

a = 381.8 × 10⁻¹⁰ cm

However, recall that:

density \ of \ unit \ cell = \dfrac{mass \ of \ unit \ cell}{volume \ of \unit \ cell}

where;

mass of unit cell = mass of atom × numbers of atoms per unit cell

Also;

mass\  of\ atom =\dfrac{ atomic \ mass}{Avogadro  \  number}

mass\  of\ atom =\dfrac{ 102.9}{6.023 \times 10^{23}}

Recall also that number of atoms in a unit cell for a  face-centered cubic = 4

So;

mass \ of \ unit \ cell= \dfrac{102.90}{6.023 \times 10^{23}}\times 4

mass of unit cell = 6.83380375 × 10⁻²² g

Density  \ of  \ unit \  cell = \dfrac{6.83380375 \times 10^{-22}}{(381.8\times 10^{-10})^3}

Density of unit cell ( rhodium) = 12.279 g/cm³

3 0
2 years ago
Controls are defined as ____​
wariber [46]

Answer:

The second one is the answer

4 0
3 years ago
Read 2 more answers
Both protons and neutrons (and their anti-particles) froze out:
VladimirAG [237]
I think Both protons and neutrons (and their anti-particles) froze out at 1013 K, about 0.0001 seconds after the Big Bang. Protons and neutrons are sub atomic particles of an atom that are found in the nucleus of an atom. Proton is the positively charge particle while the neutron has no charge. The proton positive charge accounts for the positive nuclear charge. 
6 0
3 years ago
Which element is oxidized in the reaction below? fe(co)5 (l) + 2hi (g) fe(co)4i2 (s) + co (g) + h2 (g)?
DanielleElmas [232]
Oxidation state of I is (-1) and for CO it is zero. Let's assume that the oxidation state of Fe in Fe(CO)₄I₂<span> (s) is x. For whole compound, the charge is zero.

Sum of oxidation numbers in all elements = Charge of the compound.

Here we have 1Fe , 4CO and 2I
hence we can find the oxidation state as;
 x + 4*0 + 2*(-1) = 0
 x + 0 - 2            = 0
                   x     = +2
Hence the oxidation state of Fe in product </span>Fe(CO)₄I₂ (s) is +2.

Same as we can find the oxidation state (y) of Fe in Fe(CO)₅(s).
y + 5*0 = 0
   y        = 0

Since oxidation state of Fe increased from 0 to +2, the oxidized element is Fe in the given reaction.
5 0
2 years ago
A first order reaction has a rate constant of 0. 543 at 25°C. Given that the activation energy is 75. 9 kj/mol. Calculate the ra
Rasek [7]

The rate constant of first order reaction at 32. 3 °C is 0.343 /s must be less the 0. 543 at 25°C.

First-order reactions are very commonplace. we have already encountered  examples of first-order reactions: the hydrolysis of aspirin and the reaction of t-butyl bromide with water to present t-butanol. every other reaction that famous obvious first-order kinetics is the hydrolysis of the anticancer drug cisplatin.

The value of ok suggests the equilibrium ratio of products to reactants. In an equilibrium combination both reactants and merchandise co-exist. big ok > 1 merchandise are k = 1 neither reactants nor products are desired.

Rate constant K₁  = 0. 543 /s

T₁  = 25°C

Activation energy Eₐ =  75. 9 k j/mol.

T₂ = 32. 3 °C.

K₂ =?

formula;

log K₂/K₁=  Eₐ /2.303 R [1/T₁ - 1/T₂]

putting the value in the equation  

K₂ = 0.343 /s

Hence, The rate constant of first order reaction at 32. 3 °C is 0.343 /s

The specific rate steady is the proportionality consistent touching on the fee of the reaction to the concentrations of reactants. The fee law and the specific charge consistent for any chemical reaction should be determined experimentally. The cost of the charge steady is temperature established.

Learn more about activation energy here:- brainly.com/question/26724488

#SPJ4

4 0
1 year ago
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