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3 years ago

Calcium-45 has a half-life of 162.7 days. If four half-lives have elapsed, how much time has passed?

2 answers:

7 0

Half-life is the time required for a quantity to reduce to half its initial value. If four half-lives have elapsed for calcium-45, then it would be 4x162.7 = 650.8 days have passed. Hope this answers the question. Have a nice day. Feel free to ask more questions.

Len [333]3 years ago

6 0

Answer:

1.78 years

Explanation:

First half life is the time at which the concentration of the reactant reduced to half.

Second half reaction is the time at which the remaining concentration reduced to half or the initial concentration reduced to 1/4.

Third half life is the time at which the remaining concentration reduced to half or the initial concentration reduced to 1/8.

Fourth half life is the time at which the remaining concentration reduced to half or the initial concentration reduced to 1/16.

There are four half lives. So, time has passed = 4*162.7 days = 650.8 days = 1.78 years

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3 years ago

Why does the electrical conductivity of ionic compounds change when they are dissolved in water?

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2 years ago

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3 years ago

Current is applied to a molten mixture of AgF , FeCl2 , and AlBr3 . What is produced at each electrode? STRATEGY Rank the cation

ratelena [41]

Answer:

Cathode: Ag

Anode: Br₂

Explanation:

In the cathode must occur a reduction, so it's more likely to a metal atom be in the cathode. For the metals given the reduction reactions and the potential of reduction are:

Ag⁺ + e⁻ ⇒ Ag⁰ E° = + 0.80 V

Fe⁺² + 2e⁻ ⇒ Fe⁰ E° = - 0.44 V

Al⁺³ + 3e⁻ ⇒ Al⁰ E° = -1.66 V

As the potential for Ag is the higher, the reduction will occur for it first, so in the cathode will produce Ag.

For the anode an oxidation must occurs, so the reactions for the nonmetals are:

F₂ + 2e⁻ ⇒ 2F⁻ E° = +2.87 V

Cl₂ + 2e⁻ ⇒ 2Cl⁻ E° = +1.36 V

Br₂ + 2e⁻ ⇒ 2Br⁻ E° = +1.07 V

For oxidation, the less the E°, the faster the reaction will occur, so Br₂ will be formed in the anode.

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2 years ago

Describe how water molecules interact with sodium chloride molecules in order for water to dissolve salt.

Phantasy [73]

Answer:

Sodium chloride is an ionic salt that completely dissociates in water.

Explanation:

Sodium chloride in water dissociates according to the equation.

NaCl (aq) → Na + (aq) + Cl- (aq)

While water stays in balance according to the equation

2H2O (l) ⇄ H3O+(aq) + OH-(aq).

By dissociating the solute in the solvent, the water molecules pick up the sodium cations as well as the chloride anions to break the bonds in the salt crystals and thus produce the dissolution

If the ions are analyzed separately, we see that Na + interacts with water, so it would be producing sodium hydroxide, releasing protons.

If the reaction goes in the sense of products, the Na + would increase the concentration of [H +], however being a neutral salt the pH does not vary from 7, so the reaction would never go in the sense of products, but only reagents. That's why as the sodium hydroxide is a strong base, it only promotes the formation of water and the cation.

Na+ + H2O ← NaOH + H+

The same situation occurs with chloride, since no matter how much you want to form hydrochloric acid, it dissociates by promoting the formation of water plus the corresponding anion. Na + and Cl- act as too weak conjugate acid and base, so the reaction would never go in the direction of products

Cl- + H2O ← HCl + OH-

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3 years ago