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boyakko [2]
3 years ago
15

The age of fossils can sometimes be determined by radiometric dating, which is based on the constant rate of decay of radioactiv

e isotopes. the time required for half of a radioactive isotope to decay is called the half-life of that isotope. for example, the isotope carbon-14 has a half-life of 5,730 years. suppose it is determined that a fossilized leaf contains 12.5% of the carbon-14 that was present when the fossil formed. how old is the fossil? express your answer numerically.
Chemistry
1 answer:
True [87]3 years ago
8 0
The age of the fossil given the present amount of Carbon-14 is given in the equation,
                               A(t) = A(o)(0.5)^t/h
where A(t) is the current amount, A(o) is the initial amount, t is time and h is the half-life. Substituting the known values to the equation,
                       A(t) / A(o) = 0.125 = (0.5)^(t/5730)
The value of t from the equation is 17190.
Thus, the age of the fossil is mostly likely to be 17190 years old. 
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What makes slime, slime?
Naya [18.7K]
Slime flows like a liquid, but unlike familiar liquids (e.g., oil, water), its ability to flow, or viscosity, is not constant. So it's a fluid, but not a regular liquid. Scientists call a material that changes viscosity a non-Newtonian fluid. The technical explanation is that slime is a fluid that changes its ability to resist deformation according to shear or tensile stress.

What this means is, when you pour slime or let it ooze through your fingers, it has a low viscosity and flows like a thick liquid. When you squeeze a non-Newtonian slime, like oobleck, or pound it with your fist, it feels hard, like a wet solid. This is because applying stress squeezes the particles in the slime together, making it hard for them to slide against each other.

Most types of slime are also examples of polymers. Polymers are molecules made by linking together chains of subunits.


The specifics of how a type of slime works depends on its chemical composition, but the basic explanation is that chemicals are mixed to form polymers. The polymers act as a net, with molecules sliding against each other.


Two solutions are combined to make classic slime. One is diluted school glue, or polyvinyl alcohol in water. The other solution is borax (Na2B4O7.10H2O) in water.
Borax dissolves in water into sodium ions, Na+, and tetraborate ions.
The tetraborate ions react with water to produce the OH- ion and boric acid:
B4O72-(aq) + 7 H2O <—> 4 H3BO3(aq) + 2 OH-(aq)
Boric acid reacts with water to form borate ions:
H3BO3(aq) + 2 H2O <— > B(OH)4-(aq) + H3O+(aq)
Hydrogen bonds form between the borate ion and the OH groups of the polyvinyl alcohol molecules from the glue, linking them together to form a new polymer: slime.
6 0
3 years ago
Read 2 more answers
Purification of copper can be achieved by electrorefining copper from an impure copper anode onto a pure copper cathode in an el
givi [52]

Answer: The amount of time needed to plate 14.0 kg of copper onto the cathode is 295 hours

Explanation:

We are given:

Moles of electron = 1 mole

According to mole concept:

1 mole of an atom contains 6.022\times 10^{23} number of particles.

We know that:

Charge on 1 electron = 1.6\times 10^{-19}C

Charge on 1 mole of electrons = 1.6\times 10^{-19}\times 6.022\times 10^{23}=96500C

Cu^{2+}+2e^-\rightarrow Cu

2\times 96500=193000C is passed to deposit = 1 mole of copper

63.5 g of copper is deposited by = 193000 C

14\times 1000g=14000g of copper is deposited by =\frac{193000}{63.5}\times 14000=42551181 C

To calculate the time required, we use the equation:

I=\frac{q}{t}

where,

I = current passed = 40.0 A

q = total charge = 42551181 C

t = time required = ?

Putting values in above equation, we get:

40.0=\frac{42551181 C}{t}\\\\t=1063779sec

Converting this into hours, we use the conversion factor:

1 hr = 3600 seconds

So, 1063779s\times \frac{1hr}{3600s}=295hr

Hence, the amount of time needed to plate 14.0 kg of copper onto the cathode is 295 hours

3 0
3 years ago
If thermal energy (heat) must be added to a chemical reaction in order for the reaction to take place, the reaction is _________
Harlamova29_29 [7]
<span>If thermal energy (heat) must be added to a chemical reaction in order for the reaction to take place, the reaction is endothermic. </span>
7 0
3 years ago
A student has a salt water solution. When the student adds more salt to the solution it completely dissolves. What type of solut
AlladinOne [14]

Answer:

<h2>Saturated</h2>

Explanation:

<em>A</em><em>saturated solution is a solution that contains the maximum amount of solute that is capable of being dissolved. Table salt (NaCl) readily dissolves in water.</em>

3 0
2 years ago
Read 2 more answers
Identify the Brønsted-Lowry acid, the Brønsted-Lowry base, the conjugate acid, and the conjugate base in each reaction:
ExtremeBDS [4]

Answer:

C5H5N is the base and C5H5NH+ is the conjugate acid

H2O is the acid and OH− is the conjugate base

Explanation:

<u>Hydrogen + is also called a proton</u>

C5H5N is the base because it receives the proton (H+) and C5H5NH+ is its conjugate acid

H2O is the acid  because it gives up the proton and OH− is the conjugate base because it is capable of receiving the proton

Answer:

HNO3 is the acid and NO3- is the conjugate base

H2O is the base and H3O+ is the conjugate acid

Explanation

HNO3 is the acid and NO3− is its conjugate base, capable of receiving a proton

H2O is the base because it receives the proton and H3O+ is a conjugate acid capable of giving up the proton.

3 0
3 years ago
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