Type the formula of the following compound: Aluminum nitride

A firework exploding would be an example of a(n) ________. Question 23 options: Exothermic reaction Endothermic reaction Physica

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They are Exothermic reaction

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3 years ago

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Carbon-14 if often used for radioactive dating, but it has its limitations. Uranium-238 or lead-206 are most often used to date

nexus9112 [7]

Answer:

C) The half life of carbon-14 is about 5700 years and is too short to date rocks.

Step-by-step explanation:

The practical limit for carbon dating is about nine half-lives (50 000 yr).

At that point, the amount of carbon remaining has dropped to about 0.2 % of the original amount.

The experimental uncertainties involved become so large that carbon dating is no longer reliable.

Most rocks hundreds of millions or even billions of years old.

Any radioactive carbon would have long since decayed to unmeasurable levels.

A) is wrong. Many rocks contain carbon, but they are so old that the amount of radioactive carbon has dropped below measurables.

B) is wrong. The half-life of carbon is too short to use for dating rocks.

D) is wrong. About 20 % of the carbon in rocks comes from living things that were embedded in layers of mud.

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Uranium-238 and lead-206 have half-lives of 4.5 × 10⁹ yr, which is about the age of the Earth.

Even the oldest rocks would still have half of their radioactivity, and younger rocks would have more.

Thus, U-238 and Pb-206 are ideal isotopes for measuring the ages of rocks.

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3 years ago

Burning wood in a fireplace is an example of what kind of energy conversion?

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Answer:

A. because the wood is stored chemical energy and it is converting into heat energy

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what is the half electrochemical processes and what do the half-reaction of the overall reaction represent?

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Explanation:

In an electrochemical cell, two half electrochemical processes occur. One of which is oxidation process and other is reduction process.

Oxidation reaction is defined as the reaction in which an atom looses its electrons. The oxidation number of the atom gets increased during this reaction.

$X\rightarrow X^{n+}+ne^-$

Reduction reaction is defined as the reaction in which an atom gains electrons. The oxidation number of the atom gets reduced during this reaction.

$X^{n+}+ne^-\rightarrow X$

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

Half reaction of the overall reaction represents the two processes which occur inside the cell which is oxidation and reduction.

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The representative elements are also called the Group A elements. Consider these representative elements:

lapo4ka [179]

The correct option is C.
Elements that has the same properties are usually grouped in the same group. The similarities of the elements in a group usually arise from the fact that they have the same number of electrons in their outermost shells. For instance, all elements in group 1 have one electron in their outermost shells and all elements in group 7 has seven electrons in their outermost shells. Thus, the number of a group signifies the number of electrons the elements in the group have in their outermost shells.

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