the half-life of roentgenium -281 is 17 seconds,if 10 grams are left after 85 seconds,how many grams were initially in the original sample?

Answer:

,

Explanation:

Answer:

An atom is the smallest partical in the universe that makes up everything you see around you. Every chemical element is also made up of atoms. Since atoms are what give each element their defining characteristics, each element can be composed of multiple atoms but you must have all of the same type of atoms combined in order for it to be considered an element. For example the element gold can only contain gold atoms. If you mix the atoms of one element with the atoms of another your substance has then been changed from an element to a compound.

Explanation:

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Explanation:

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Answer:

distance decreases and force increases

Explanation:

When we use a simple machine to do work, the distance decreases, the force increases. Hence, option D is correct. Because, these parameters are in inverse proportion.

Force is an external agent acting on a body to change its motion. There are various kinds of force such as frictional force, magnetic force, gravitational force etc.

Work done is the effectiveness of the machine to use the force to make the maximum displacement. Work done is the product of force and distance.

W = F.ds

As per this relation, the force acting on large distance makes greater work done. However,

F = W/ds.

Hence, as the distance increases, the force is decreasing. Therefore, option D is correct.

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Answer:

In physics, the kinetic energy of an object is the energy that it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes. The same amount of work is done by the body when decelerating from its current speed to a state of rest.

In classical mechanics, the kinetic energy of a non-rotating object of mass m traveling at a speed v is 1/2*mv^2. In relativistic mechanics, this is a good approximation only when v is much less than the speed of light.

The standard unit of kinetic energy is the joule, while the English unit of kinetic energy is the foot-pound.

Explanation:

Don't directly copy and paste this because you will get flagged for plagiarism. Just type this out in your own words and change a few of the words to their synonyms.

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Answer:

Metallic character increases down each Group of the Table as the outer electrons are further from the nucleus and require less energy for their removal. (a) metallic character decreases from left to right in each Period.

Explanation:

The metallic character increases down each Group on the periodic table.

The metallic character decreases from left to right in each Period.

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Answer:

5000mm

Explanation:

10mm makes 1 cm

so if we compare them:

10mm-->1cm

x -->500cm

now cross multiply:

1x-->5000

divide both sides by 1 for x to be alone

therefore we get x=5000

Answer:

They are constitutional isomers and diastereomers.

Answer:

Simply put, essential amino acids are amino acids that cannot be made by the body. These amino acids must come from a person's diet, as the human body lacks the metabolic pathways required to synthesize these amino acids. ... Nonessential amino acids do not need to come from the diet.

Explanation:

hope it helps you

Answer:

D

Explanation:

Lamps

Answer:

a) 2.7 g cm³

b) 10.2 g

Explanation:

a) Density = Mass/Volume

= 21.6/8.00

= 2.7 g cm³

b) Mass = Volume × Density

= 2.55 × 4.0

= 10.2 g

Answer:

a

Explanation:

its formed from sodium and sodium metal is produced by electrolysis of dry molten sodium chloride.

Answer:

Strontium

Explanation:

strontium will be less reactive because reactivity decreases down the group

Answer:

158 grams

Explanation:

Answer:

A mineral has to be naturally occurring, inorganic, solid, have a crystal structure, and have a definite chemical composition.

Explanation:

Answer:

Water separates the two reactants into two layers, stopping the reaction.

Explanation:

Maleic anhydride can and will react with water.

The reaction between maleic anhydride and anthracene is a Diels Alder reaction. This type of reaction is a cycloaddition reaction.

The Diels Alder reaction is a member of a class of reactions called cycloadditions. This reaction involves three pi bonds, two from the diene and one from the dienophile in a concerted reaction to give a six-membered ring.

Since this reaction involves four pi electrons in the diene and two pi electrons from the dienophile, it is sometimes referred to as a 4+2 cycloaddition.

The presence of electron donating groups on the diene and the electron withdrawing groups on the dienophile favors normal Diels Alder reactions. The reaction involves the formation of new σ bonds which are energetically more stable than π bonds.

Anthracene can react with water, breaking the center ring. Maleic anhydride can react with water, opening its ring. The reactants get seperated into two layers by water and thereby stops the reaction.

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Answer:

A theory of physics in which energy exists only in discrete quantities, called quanta. It was originated in 1900 by the German physicist Max Karl Ernst Ludwig Planck (1858–1947), who suggested that electromagnetic radiation is quantized, i.e. it can be emitted or absorbed only in tiny packets, not continuously.

Explanation:

Answer:

D. Communication of results

Answer:

b.

conclusion

because it gives the overall information about the experiment

Answer:

It allows the traveler to justify questionable expense items.

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Answer:

The answer is B. False

Explanation:

Answer:

Coloured candies?

Explanation:

Answer:

i think it would be answer D

Explanation:

Answer: Water

Explanation: During photosynthesis, plants take in carbon dioxide (CO2) and water (H2O) from the air and soil

Answer:

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Explanation:

Answer:

2.75

Explanation:

D= [tex]\frac{mass}{volume}[/tex]

[tex]\frac{22}{8}[/tex]= 2.75

Hope this helps!

Answer:

D. The ratio of the substances coefficients equals the ratio of their numbers of moles.

Melting points of enantiomers will not compare to each other as they have same M.P. and Diastereoisomers are compared on the basis of melting point.

Stereoisomers are those isomers which are having the same molecular formula but different spatial arrangemet of atoms within the molecule.

Hence, only diastereoisomers are compared on the basis of melting point.

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Answer:

about 5 years i think

Explanation:

I've tried all the methods i know

it's about 5 years

hope it helps

The age of the artifact is equal to 2.5 × 10³ years when the half-life of carbon- 14 is 5.73 × 10³ years.

The half-life of a radioactive element is defined as the time that is required to decrease the original quantity of a radioactive isotope to half after decay.

The half-life of a radioactive isotope is the feature of the element and does not depend upon the actual amount of the radioactive isotope.

Given, the ratio of the initial and left amount of  ¹⁴C is :

N = 0.745 N₀

The half-life period of the ¹⁴C isotope = 5.73 × 10³ years

The rate constant of the decay of radioisotope can be calculated from the below-mentioned formula:

[tex]\displaystyle k=\frac{0.693}{t_{1/2}}[/tex]

[tex]\displaystyle k=\frac{0.693}{5.73 \times 10^3}[/tex]

k = 0.123 × 10⁻³ yr⁻¹

The age of the artifact can be calculated as:
[tex]\displaystyle t =\frac{2.303}{k} log\frac{N_0}{N}[/tex]

[tex]\displaystyle t =\frac{2.303}{0.123\times 10^{-3}} log\frac{N_0}{0.735 N_0}[/tex]

t = 2.5 × 10³ years

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