One element of the circulatory system is the _________

What is the half-life of an isotope that decays to 6.25% of its original activity in 18.9 hours?

inessss [21]

Radioactive material obeys 1st order decay kinetics,
For 1st order reaction, we have
k = $\frac{2.303}{t}Xlog \frac{\text{initial conc.}}{\text{final conc.}}$
where, k = rate constant of reaction

Given: Initial conc. 100, Final conc. = 6.25, t = 18.9 hours

∴ k = $\frac{2.303}{18.9} X log \frac{100}{6.25}$ = 0.1467 hours^(-1)

Now, for 1st order reactions: half life = $\frac{0.693}{k} = \frac{0.693}{0.1467}$ = 4.723 hours.

8 0

3 years ago

Concentrated nitric acid used in laboratory work is 68% nitric acid by mass in aqueous solution. What should be the molarity of

dsp73

The first thing we need to do here is to recognize the unit of molarity and the units of the given percentage of nitric acid.

Molarity is mol HNO3 / L of solution. This is our aim

The given percentage is 0.68 g HNO3/ g solution

multiplying this with density to convert g solution into mL solution and dividing with the molecular weight of HNO3 (63 g/mol) to convert g HNO3 to mol. Therefore we obtain

0.016 mol/ mL or 16.23 mol/ L (M)

6 0

3 years ago

What is the difference between the small and large intestines?

nalin [4]

Ggggggggggggggggggggggggggggggggggggggg

3 0

2 years ago

How much liquid does this graduated cylinder contain?

nikklg [1K]

Answer:

I think 44 mL

Explanation:

I hope this helps u :D

8 0

3 years ago

Use the standard half-cell potentials listed below to calculate the standard cell potential for the following reaction occurring

Lady_Fox [76]

Answer:

The standard cell potential is 1.40 V. The correct option is the option D (+1.40 V)

Explanation:

Oxide-reduction reactions, also called redox, involve the transfer or transfer of electrons between two or more chemical species. In these reactions two substances interact: the reducing agent and the oxidizing agent.

An oxidizing element or oxidizing agent is one that reaches a stable energy state as a result of which the oxidant is reduced and gains electrons. The oxidizing agent causes oxidation of the reducing agent generating the loss of electrons of the substance and, therefore, oxidizes in the process.

In other words, the oxidizing agent is that chemical species that in a redox process accepts electrons released by the reducing agent and, therefore, is reduced in said process. The oxidizing agent is reduced because, upon receiving electrons from the reducing agent, a decrease in the value of the charge or oxidation number of one of the atoms of the oxidizing agent is induced .

Electrochemical cells, galvanic cells or batteries are called devices that are capable of transforming chemical energy originated in a spontaneous redox process into electrical energy.

The cellular potential is generally in standard conditions, that is, 1 M with respect to solute concentrations in solution and 1 atm for gases.

In this case you have the reaction:

3 Cl₂(g) + 2 Fe(s) → 6 Cl⁻(aq) + 2 Fe³⁺(aq)

In this case the following half-reactions occur:

Semi-reaction of oxidation ( an atom or group of atoms loses electrons, or increases its positive charges): Fe³⁺(aq) + 3 e- -->Fe(s); E⁰ = -0.04 V

Semi-reaction of reduction (an atom or group of atoms gains electrons, increasing its negative charges): Cl₂(g) + 2 e- --> 2 Cl-(aq); E⁰=1.36 V

In an electrochemical cell at 25°C the potentials of the semi-reactions are usually measured in the sense of reduction and generally the standard potential between both electrochemical cells will be:

$E^{0} =E^{0} _{reduction} -E^{0} _{oxidation}$

E⁰=1.36 V - (-0.04 V)

E⁰=1.36 V + 0.04 V

E⁰=1.40 V

The standard cell potential is 1.40 V. The correct option is the option D (+1.40 V)

7 0

3 years ago

One element of the circulatory system is the __________.