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geniusboy [140]
2 years ago
8

A radioactive substance has a half-life of 5 million years. What is the age of a rock in which 25% of the original radioactive a

toms remain? You must show your work or explain how you came up with your answer for full credit.
Chemistry
1 answer:
GenaCL600 [577]2 years ago
5 0

Answer:

10 million years

Explanation:

For a sample to decay to 25% of its original amount, 2 half lives must have passed. Since one half life is 5 million years, multiplying this by 2 gives us that 2 half lives is 10 million years.

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Need help asap with this chemistry if someone could help me
Burka [1]

Answer:

<h3>1)</h3>

Structure One:

  • N: -2
  • C: 0
  • O: +1

Structure Two:

  • N: 0
  • C: 0
  • O: -1

Structure Three:

  • N: -1
  • C: 0
  • O: 0.

Structure Number Two would likely be the most stable structure.

<h3>2)</h3>
  • All five C atoms: 0
  • All six H atoms to C: 0
  • N atom: +1.

The N atom is the one that is "likely" to be attracted to an anion. See explanation.

Explanation:

When calculating the formal charge for an atom, the assumption is that electrons in a chemical bond are shared equally between the two bonding atoms. The formula for the formal charge of an atom can be written as:

\text{Formal Charge} \\ = \text{Number of Valence Electrons in Element} \\ \phantom{=}-\text{Number of Chemical Bonds} \\\phantom{=} - \text{Number of nonbonding Lone Pair Electrons}.

For example, for the N atom in structure one of the first question,

  • N is in IUPAC group 15. There are 15 - 10 = 5 valence electrons on N.
  • This N atom is connected to only 1 chemical bond.
  • There are three pairs, or 6 electrons that aren't in a chemical bond.

The formal charge of this N atom will be 5 - 1 - 6 = -2.

Apply this rule to the other atoms. Note that a double bond counts as two bonds while a triple bond counts as three.

<h3>1)</h3>

Structure One:

  • N: -2
  • C: 0
  • O: +1

Structure Two:

  • N: 0
  • C: 0
  • O: -1

Structure Three:

  • N: -1
  • C: 0
  • O: 0.

In general, the formal charge on all atoms in a molecule or an ion shall be as close to zero as possible. That rules out Structure number one.

Additionally, if there is a negative charge on one of the atoms, that atom shall preferably be the most electronegative one in the entire molecule. O is more electronegative than N. Structure two will likely be favored over structure three.

<h3>2)</h3>

Similarly,

  • All five C atoms: 0
  • All six H atoms to C: 0
  • N atom: +1.

Assuming that electrons in a chemical bond are shared equally (which is likely not the case,) the nitrogen atom in this molecule will carry a positive charge. By that assumption, it would attract an anion.

Note that in reality this assumption seldom holds. In this ion, the N-H bond is highly polarized such that the partial positive charge is mostly located on the H atom bonded to the N atom. This example shows how the formal charge assumption might give misleading information. However, for the sake of this particular problem, the N atom is the one that is "likely" to be attracted to an anion.

5 0
3 years ago
Select the pair that consists of a base and its conjugate acid in that order. CO32−/CO22−
lana [24]

Answer: The pair that consists of a base and its conjugate acid in that order.NH_3/NH_4^+

Explanation:

According to the Bronsted-Lowry conjugate acid-base theory, an acid is defined as a substance which looses donates protons and thus forming conjugate base and a base is defined as a substance which accepts protons and thus forming conjugate acid.

H_3PO_4\rightarrow H_PO_4{2^-}+2H^+

H_2CO_3\rightarrow HCO_3^-+H^+

NH_3+H^+\rightarrow NH_4^+

HCO_3^-\rightarrow CO_3^{2-}+H^+

NH_3  is gaining a proton, thus it is considered as a brønsted-lowry base and after gaining a proton, it formsNH_4^+  which is a conjugate acid.

3 0
3 years ago
What are the uses of carbon-14?
Gelneren [198K]

Carbon-14 is a radioactive isotope used to date organic material. Its consistent rate of decay allows the age of an object to be determined by the proportion of carbon-14 to other carbon isotopes. This process is called radiocarbon dating. Carbon-14 is also used as a radioactive tracer for medical tests.

6 0
3 years ago
What is the structure of 3_methyl cyclopropane
lisabon 2012 [21]

Answer:

structure formula C3H5CH3

6 0
3 years ago
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MissTica
B and temp is related to kinetic energy by how they both effect the speed of the particles. If the temp is hot the particles speed up and if cold the particles slow down
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