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3 years ago

What is a half-life?

Chemistry

1 answer:

Travka [436]3 years ago

4 0

Answer:

An interesting and useful aspect of radioactive decay is half-life, which is the amount of time it takes for one-half of a radioactive isotope to decay. The half-life of a specific radioactive isotope is constant; it is unaffected by coTnditions and is independent of the initial amount of that isotope.

Explanation:

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In order to derive a simplified version of the Nernst equation by assuming standard temperature we can substitute which of the f

Nikitich [7]

Answer:

c. 298 K

Explanation:

Nernst equation is an equation used in electrochemistry that relates the reduction potential of a reaction with the standard potential, temperature and concentrations of the reactants in that are been reducted and oxidized. The formula is:

E = E° - RT / nF ln [Red] / [Ox]

<em>Where R is gas constant (8.314J/molK), T is absolute temperature (In Kelvin), n are moles of electrons and F is faraday constant (K/Volt*mol)</em>

<em />

In electrochemistry, standard temperature is taken as 298K. That means by assuming standard temperature we can substitute T as:

5 0

3 years ago

Calculate the empirical formula of a compound that has a composition of 5.9% (by mass) hydrogen and 94.1% (by mass) oxygen.

adelina 88 [10]

Answer:

The empirical formula is the simplest form;

Given:

Oxygen O at 94.1% and

H at 5.9%

Assume 100grams.

94% = 0.941 x 100gm. = 94.1 gm x 1mole/16gm. = 5.88 moles of O

5.9% = 0.059 x 100gm. = 5.9gm. X 1moleH/1.002gm. = 5.88 moles of H

There is one mole of O for each mole of H so the empirical formula is $O_1H_1$

and written as OH.

8 0

3 years ago

Read 2 more answers

If the formula for potassium chlorate is KClO3 and the formula for magnesium fluoride is MgF2, then what isthe formula for magne

mr_godi [17]

The formula for magnesium chlorate is Mg(ClO3)2.

5 0

3 years ago

Determine the mass of CuSO4 • 5H20 that must be used to prepare 250mL of 2.01 M CuSO4(aq).

mario62 [17]

Given parameters:

Volume of CuSO₄ = 250mL

Concentration of CuSO₄ = 2.01M

Unknown:

Mass of CuSO₄.5H₂O = ?

To solve this problem, we must write the chemical relationship between both species.;

CuSO₄.5H₂O → CuSO₄ + 5H₂O

Now that we know the expression, it is possible to solve for the unknown mass.

First find the number of moles of CuSO₄;

Number of moles = Concentration x Volume

Take 250mL to L so as to ensure uniformity of units;

Volume = 250 x 10⁻³L

Input the parameters and solve for number of moles;

Number of moles = 250 x 10⁻³ x 2.01 = 0.5mol

From the equation;

1 mole of CuSO₄ is produced from 1 mole of CuSO₄.5H₂O

So 0.5 moles of CuSO₄ will be produced from 0.5 moles of CuSO₄.5H₂O

Now let us find the molar mass of CuSO₄.5H₂O = 63.6 + 32 + 4(16) + 5(2x1 + 16) = 249.6g/mole

Mass of CuSO₄.5H₂O = number of moles x molar mass

= 0.5 x 249.6

= 124.8g

The mass of CuSO₄.5H₂O is 124.8g

5 0

4 years ago

In the process of attempting to characterize a substance, a chemist makes the following observations: (a) The substance is a sil

Amiraneli [1.4K]

The question is incomplete, this is the complete question;

In the process of attempting to characterize a substance, a chemist makes the following observations. Which are physical properties and which are chemical properties?

(a) The substance is a silvery white, lustrous metal.

(b) The substance melts at 649 ∘C

(d) The density of the substance at 20 ∘C is 1.738 g/cm³.

(e) The substance burns in air, producing an intense white light.

(f) The substance reacts with chlorine to give a brittle white solid.

(g) The substance can be pounded into thin sheets or drawn into wires.

(h) The substance is a good conductor of electricity.

Answer:

(a) Physical

(b) Physical

(d) Physical

(e) Chemical

(f) Chemical

(g) Physical

(h) Physical

Explanation:

(a) The substance is a silvery white, lustrous metal - is appearance which is physical.

(b) The substance melts at 649 ∘C metling point is a physical measurement

(d) The density of the substance at 20 ∘C is 1.738 g/cm3 how heavy a substance is,is physical.

(e) The substance burns in air, producing an intense white light. Burning is a chemical change. It is a reaction of a substance with oxygen

(f) The substance reacts with chlorine to give a brittle white solid. This is a chemical reaction as the question says.

(g) The substance can be pounded into thin sheets or drawn into wires. Ductility is a physical change, the substance remains chemically unchanged

(h) The substance is a good conductor of electricity. Any conductivity is physical, the substance remains chemically unchanged

7 0

3 years ago