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3 years ago

How many half -lives are required for three-fourths of the nuclei of an istope in a sample decay

1 answer:

7 0

The half life of a radio-isotope is the amount of time required for half of the isotope to decay into a new element or sister isotope. One half life results in a 50% loss of radioisotope, and two half lives results in a 75% loss. For three-fourths of the nuclei to decay, two half-lives must pass.

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3. The opening that allows light to enter the eye is the

xxMikexx [17]

Answer:

A) Iris

Explanation:

The Iris controls the diameter of the opening in your eye, thus also controlling the amount of light let inside. It's also reponsible for the colour of you eye.

4 0

2 years ago

Read 2 more answers

Which of the following statements is true about what happens during a chemical reaction?

tiny-mole [99]

Answer: The correct option is A.

Explanation: In a chemical reaction, reactants react to form a number of products.

For the formation of products, the bonds of the individual reactants must be broken and the bonds of the products must be formed.

For example: Formation of water from hydrogen gas and oxygen gas. Reaction follows:

$2H_2(g)+O_2(g)\rightarrow 2H_2O(l)$

The Bonds of hydrogen and oxygen molecule are broken and new bonds between hydrogen and oxygen atoms are formed to give water molecule.

5 0

2 years ago

Read 2 more answers

The isotope 208Tl undergoes Î² decay with a half-life of 3.1 min.

melamori03 [73]

Answer:

a. Pb 208

b. About 21.7 minutes

c. only a trace amount

Explanation:

It under goes beta decay.

There should be virtually nothing after an hour

8 0

3 years ago

3. Write DISSOCIATION or IONIZATION equations for the following chemicals:

Romashka [77]

Answer:

a) HNO3 -> H+ + NO3- disassociation of Nitric Acid; to yield a Nitrate ion and a Proton, H+, or as a Hydronium ion H3O+

b) H2S04 -> Disassociation of Sulfuric Acid; simple way- 2H+ + SO4- -

c) H2S hydrogen sulphide in water is an acid; thus H+ HS- disassociation.

d) NaOH -> dissociation of Na+ + OH-; this is complete; sodium hydroxide is deliquescent, meaning it will draw water - EVEN from the air! Strong Base

e) Na2CO3 -> 2Na+ CO3- - Ionization of sodium carbonate - a salt

f) Na2S04 -> 2Na+ + SO4 - - ionization of sodium sulphate - a salt

g) NaCl -> Na+ + Cl- ionization of the salt, Sodium Chloride

Explanation:

Salts ionize at different rates; acids or bases dissociate; these are mostly strong acids and NaOH, a strong base.

8 0

3 years ago

The student is now told that the four solids, in no particular order, are aluminum chloride (AlCl3), sugar (C6H12O6), benzoic ac

zaharov [31]

Answer:

AlCl₃, NaBr, C₆H₅COOH, C₆H₁₂O₆.

Explanation:

The more ions in solution, the greater the conductivity of a solution because these charged particles can carry electrons in the solution.

In the first place, when AlCl₃ dissolves in water it produces 4 ions:

AlCl₃(aq) ⇄ Al³⁺(aq) + 3 Cl⁻(aq)

If the solution is 0.20M in AlCl₃, it will be 4 x 0.20M = 0.80M in ions.

Secondly, NaBr is a strong electrolyte (complete ionization) so it produces 2 moles of ions per each mole of NaBr dissolved:

NaBr(aq) ⇄ Na⁺(aq) + Br⁻(aq)

If the solution is 0.20M in NaBr, it will be 2 x 0.20M = 0.40M in ions.

Then, benzoic acid is a weak electrolyte (partial ionization) so it will produce less than 2 moles of ions per each mole of benzoic acid dissolved:

C₆H₅COOH(aq) ⇄ C₆H₅COO⁻(aq) + H⁺(aq)

If the solution is 0.20M in benzoic acid, the solution will be far below 0.40M in ions.

Finally, sugar has only nonpolar covalent bonds so it will produce no ions in solution, thus being a poor electricity conductor.

4 0

3 years ago