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3 years ago

Approximately _____ elements occur naturally on earth.

Chemistry

2 answers:

boyakko [2]3 years ago

5 0

90 elements occur naturally on earth.

Aliun [14]3 years ago

4 0

For the answer to the question above, the number of naturally occurring elements is actually in dispute, believe it or not. Some say 98, others say 88 and all cite various reasons. The traditionally accepted answer would be 92.
I hope this helps.

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How many oxygen atoms are there in 6.00 g of sodium dichromate, na2cr2o7?

mel-nik [20]

Answer is: there are 9,7·10²² atoms of oxygen.
m(Na₂Cr₂O₇) = 6,00 g.
n(Na₂Cr₂O₇) = m(Na₂Cr₂O₇) ÷ M(Na₂Cr₂O₇).
n(Na₂Cr₂O₇) = 6 g ÷ 262 g/mol.
n(Na₂Cr₂O₇) = 0,023 mol.
n(Na₂Cr₂O₇) : n(O) = 1 : 7.
n(O) = 7 · 0,023 mol.
n(O) = 0,161 mol.
N(O) = 0,161 mol · 6,022·10²³ 1/mol.
N(O) = 9,7·10²².

6 0

3 years ago

What is the calculated value of the cell potential at 298K for an

Tpy6a [65]

The question is incomplete, here is the complete question:

What is the calculated value of the cell potential at 298 K for an electrochemical cell with the following reaction, when the H₂ pressure is 6.56 x 10⁻² atm, the H⁺ concentration is 1.39 M, and the Sn²⁺ concentration is 9.35 x 10⁻⁴ M?

$2H^+(aq)+Sn(s)\rightarrow H_2(g)+Sn^{2+}(aq)$

Answer: The cell potential of the given electrochemical cell is 0.273 V

Explanation:

For the given chemical equation:

$2H^+(aq)+Sn(s)\rightarrow H_2(g)+Sn^{2+}(aq)$

The half cell reactions for the given equation follows:

Oxidation half reaction: $Sn(s)\rightarrow Sn^{2+}(aq)+2e^-;E^o_{Sn^{2+}/Sn}=-0.14V$

Reduction half reaction: $H_2+2e^-\rightarrow H_2(g);E^o_{2H^{+}/H_2}=0.0V$

Oxidation reaction occurs at anode and reduction reaction occurs at cathode.

To calculate the $E^o_{cell}$ of the reaction, we use the equation:

$E^o_{cell}=E^o_{cathode}-E^o_{anode}$

Putting values in above equation, we get:

$E^o_{cell}=0.0-(-0.14)=0.14V$

To calculate the EMF of the cell, we use the Nernst equation, which is:

$E_{cell}=E^o_{cell}-\frac{0.059}{n}\log \frac{[Sn^{2+}]\times p_{H_2}}{[H^+]^2}$

where,

$E_{cell}$ = electrode potential of the cell = ?

$E^o_{cell}$ = standard electrode potential of the cell = +0.14 V

n = number of electrons exchanged = 2

$[H^{+}]=1.39M$

$[Sn^{2+}]=9.35\times 10^{-4}M$

$p_{H_2}=6.56\times 10^{-2}atm$

Putting values in above equation, we get:

$E_{cell}=0.14-\frac{0.059}{2}\times \log(\frac{(9.35\times 10^{-4})\times (6.56\times 10^{-2})}{(1.39)^2})\\\\E_{cell}=0.273V$

Hence, the cell potential of the given electrochemical cell is 0.273 V

4 0

2 years ago

A(n) ________________ is a structure or behaviors in organisms that help them survive in their environment.

Lapatulllka [165]

Answer:

Adaptations

Explanation:

Adaptation is simply defined as a specific characteristics of an animal or plant which can be a body part, body covering, or behavior that helps an animal or plant survive in its environment.

The common types of Adaptations includes Physical adaptation which entails a change to a part of the body and Behavioral adaptation which is simply what an animal does in response to an external stimulus.

Examples of Adaptation includes Hibernation, Camouflage, Mimicry, Whiskers, Beaks and others. In plants, seed colour, hard endocarp, secretions e. t. c helps them survive in their environment.

6 0

3 years ago

how would physical changes to Earth such as an iceberg or rising sea levels lead to physical changes in organisms?

vlabodo [156]

If there was more water area and less land more animals would adapt to the water life than land. Like for example more evolving fins or even amphibians
just staying in water and no longer needing legs or the things they use for living on the land.

7 0

3 years ago

In a given substance, as the temperature of a substance increases, the volume of that substance

steposvetlana [31]

C. Increases. Increasing temperature=Increasing Volume

3 0

2 years ago