Chemistry, 25.11.2020 14:20 ashleyann3052

Indium-116 is radioactive and has a half life of 14.10 seconds. How long would it take a sample to decay from 7.70 mg to 900 µg.

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Answer from: ayoismeisjuam

43.73 seconds

Explanation:

Half-life of indium = 14.10 sec

First we have to calculate the rate constant, we use the formula :

$k=\frac{0.693}{t_\frac{1}{2}}$

$k=\frac{0.693}{14.10}=0.0491sec^{-1}$

Now we have to calculate the age of the sample:

Expression for rate law for first order kinetics is given by:

$t=\frac{2.303}{k}\log\frac{a}{a-x}$

where,

k = rate constant

t = age of sample = ?

a = initial amount of the reactant = 7.70 mg= $7700\mug$

$(1mg=1000\mug$

a - x = amount left after decay process = $900\mug$

Now put all the given values in above equation, we get

$t=\frac{2.303}{0.0491}\log\frac{7700}{900}$

t=43.73sec

Thus it would take 43.73 seconds sample to decay from 7.70 mg to 900 µg.

Answer from: Quest

assuming that your periodic table has eighteen columns, you should highlight the four elements in the third column from the left of the table.

explanation

neutral atoms of elements after calcium contain d electrons. the energy of d orbitals of a particular main shell lies between the energy of the s and p orbitals of the next main shell. for example, electrons in the $3d$ have energy higher than those in the $4 s$ orbital while lower than those of the $4 p$ orbital.

by the aufbau principle, electrons fill orbitals one at a time, starting from those of the lowest energy. the $4s$ orbital is therefore filled right after $3p$ orbitals and before $3 d$ orbitals.

potassium has electron configuration $[\text{ar}] 4 s^{1}$ and calcium $[\text{ar}] 4 s^{2}$ . the s orbital of a main shell holds a maximum of two electrons. the next element would thus have the electron configuration $[\text{ar}] 4 s^{2} \; 3d^{1}$ and satisfy the requirements.

a neutral atom of the element contains three electrons on top of the most recent noble gas element. it should thus be placed in the third column of the periodic table. both scandium and yttrium would satisfy the conditions. an aufbau diagram indicates that the 4f orbital is filled before the 5d. however, it appears that exceptions exists for both lanthanum and actinium. neutral atoms of the two d-block elements also demonstrate the $ns^{2} \; (n-1) p^{1}$ and should be highlighted as well.

Answer from: Quest

So what you would do is go through and add 3 teaspoons(tsp) 6 times because of the 6 tablespoons(tbsp). which will give you an answer of 18. another way is to multiply 3x6=18.

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Indium-116 is radioactive and has a half life of 14.10 seconds. How long would it take a sample to d...

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