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3 years ago

How many half-lives must elapse until 84 % of a radioactive sample of atoms has decayed? -g?

1 answer:

4 0

Half-life is the time required for decay of 50% of radio-active nuclei.

Thus, when radio-active material crosses 1st half-life, 100/2 = 50% radio-active material is left and remaining 50% is elapsed.

When, when radio-active material crosses 2nd half-life, 50/2 = 25% radio-active material is left and remaining 75% is elapsed.

When radio-active material crosses 3rd half-life, 25/2 = 12.5% radio-active material is left and remaining 87.5% is elapsed.

Thus, 2 half-lives must elapse until 84 % of a radioactive sample of atoms has decayed.

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What coefficient of h+ balances the atoms in this half-reaction h+ + mno2 → mn2+ + h2o?

kvv77 [185]

The answer is 4 im pretty sure

7 0

3 years ago

Read 2 more answers

HELP PLEASE THE OTHER 'ANSWER' ISNT EVEN AN ANSWER!

hodyreva [135]

Answer:

most likely that (2) the replicated experiment was performed incorrectly.

Why, u ask? u dare question me:

1- The initial experiment invalidness cannot be proven.

2- the second answer is correct

3- Different labaratories does not effect the outcome, as long as the parameter and environment of the replicated experiment is the same as when the initial experiment was conducted.

4- Already knowing the data and errors would increase the precision of the replicated experiment.

5- Change in variables should still be in the objective (or purpose) of the experiment, thus, major difference in the outcome should not happen.

happy learning!

4 0

3 years ago

Does anyone know how to do this ??

lord [1]

Answer:

Look at your periodic table

Explanation:

It tells you everything like Potasium 1 and 1 ox and 1 hydrogen

7 0

3 years ago

A salt is best described as a compound that is formed from the reaction between

kaheart [24]

Answer:

Explanation:

5 0

4 years ago

A 4.36 g sample of an unknown alkali metal hydroxide is dissolved in 100.0 ml of water. an acid-base indicator is added and the

Fofino [41]

Answer:

(a) $102.6g/mol$

(b) Rubidium

Explanation:

Hello,

This titration is carried out by assuming that the volume of base doesn't have a significant change when the mass is added, thus, we state the following data a apply the down below formula to compute the molarity of the base solution:

$V_{base}=0.1L; M_{acid}=2.5M, V_{acid}=0.017L\\V_{base}M_{base}=V_{acid}M_{acid}$

Solving for the molarity of base we've got:

$M_{base}=\frac{M_{acid}*V_{acid}}{V_{base}}=\frac{2.50M*0.017L}{0.1L} =0.425M=0.425mol/L$

Now, we can compute the moles of the base as:

$n_{base}=0.425mol/L*0.1L=0.0425mol$

(a) Now, one divides the provided mass over the previously computed moles to get the molecular mass of the unknown base:

$\frac{4.36g}{0.0425mol} =102.6g/mol$

(b) Subtracting the atomic mass of oxygen and hydrogen, the metal's atomic mass turns out into:

$102.6g/mol-16g/mol-1g/mol=85.6g/mol$

So, that atomic mass dovetails to the Rubidium's atomic mass.

Best regards.

8 0

3 years ago