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GrogVix [38]
2 years ago
6

Thallium-207 decays exponentially with a half life of 4.5 minutes. if the initial amount of the isotope was 28 grams, how many g

rams of the isotope will remain after 7 minutes?
Chemistry
1 answer:
Agata [3.3K]2 years ago
7 0
An exponential decay law has the general form: A = Ao * e ^ (-kt) =>

A/Ao = e^(-kt)

Half-life time => A/Ao = 1/2, and t = 4.5 min

=> 1/2 = e^(-k*4.5) => ln(2) = 4.5k => k = ln(2) / 4.5 ≈ 0.154

Now replace the value of k, Ao = 28g  and t = 7 min to find how many grams of Thalium-207 will remain:

A = Ao e ^ (-kt) = 28 g * e ^( -0.154 * 7) = 9.5 g

Answer 9.5 g.
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Identify the precipitate(s) formed when solutions of na2so4(aq), ba(no3)2(aq), and nh4clo4(aq) are mixed.
Lostsunrise [7]

Answer : BaSO_{4} will be the precipitate which will be formed.


Explanation : When all the three solutions namely; NaSO_{4}  + Ba(NO_{3})_{2}  + NH_{4} ClO_{4} are mixed together a white precipitate of BaSO_{4} is formed as a product in the solution along with the soluble by product of Ammonium nitrate which is NH_{4} NO_{3} 

7 0
2 years ago
A student reacts 20.0 mL of 0.248 M H2SO4 with 15.0 mL of 0.195 M NaOH. Write a balanced chemical equation to show this reaction
Molodets [167]

<u>Answer:</u> The concentration of salt (sodium sulfate), sulfuric acid and NaOH in the solution is 0.0418 M, 0.0999 M and 0 M respectively.

<u>Explanation:</u>

To calculate the number of moles for given molarity, we use the equation:

\text{Molarity of the solution}=\frac{\text{Moles of solute}}{\text{Volume of solution (in L)}}     .....(1)

<u>For NaOH:</u>

Initial molarity of NaOH solution = 0.195 M

Volume of solution = 15.0 mL = 0.015 L   (Conversion factor:   1 L = 1000 mL)

Putting values in equation 1, we get:

0.195M=\frac{\text{Moles of NaOH}}{0.015L}\\\\\text{Moles of NaOH}=(0.195mol/L\times 0.015L)=2.925\times 10^{-3}mol

<u>For sulfuric acid:</u>

Initial molarity of sulfuric acid solution = 0.248 M

Volume of solution = 20.0 mL = 0.020 L

Putting values in equation 1, we get:

0.248M=\frac{\text{Moles of }H_2SO_4}{0.020L}\\\\\text{Moles of }H_2SO_4=(0.248mol/L\times 0.020L)=4.96\times 10^{-3}mol

The chemical equation for the reaction of NaOH and sulfuric acid follows:

2NaOH+H_2SO_4\rightarrow Na_2SO_4+2H_2O

By Stoichiometry of the reaction:

2 moles of NaOH reacts with 1 mole of sulfuric acid

So, 2.925\times 10^{-3} moles of KOH will react with = \frac{1}{2}\times 2.925\times 10^{-3}=1.462\times 10^{-3}mol of sulfuric acid

As, given amount of sulfuric acid is more than the required amount. So, it is considered as an excess reagent.

Thus, NaOH is considered as a limiting reagent because it limits the formation of product.

Excess moles of sulfuric acid = (4.96-1.462)\times 10^{-3}=3.498\times 10^{-3}mol

By Stoichiometry of the reaction:

2 moles of KOH produces 1 mole of sodium sulfate

So, 2.925\times 10^{-3} moles of KOH will produce = \frac{1}{2}\times 2.925\times 10^{-3}=1.462\times 10^{-3}mol of sodium sulfate

  • <u>For sodium sulfate:</u>

Moles of sodium sulfate = 1.462\times 10^{-3}moles

Volume of solution = [15.0 + 20.0] = 35.0 mL = 0.035 L

Putting values in equation 1, we get:

\text{Molarity of sodium sulfate}=\frac{1.462\times 10^{-3}}{0.035}=0.0418M

  • <u>For sulfuric acid:</u>

Moles of excess sulfuric acid = 3.498\times 10^{-3}mol

Volume of solution = [15.0 + 20.0] = 35.0 mL = 0.035 L

Putting values in equation 1, we get:

\text{Molarity of sulfuric acid}=\frac{3.498\times 10^{-3}}{0.035}=0.0999M

  • <u>For NaOH:</u>

Moles of NaOH remained = 0 moles

Volume of solution = [15.0 + 20.0] = 35.0 mL = 0.035 L

Putting values in equation 1, we get:

\text{Molarity of NaOH}=\frac{0}{0.050}=0M

Hence, the concentration of salt (sodium sulfate), sulfuric acid and NaOH in the solution is 0.0418 M, 0.0999 M and 0 M respectively.

8 0
2 years ago
If the reaction shown below is exothermic, the energy level of the reactants is ________. h2 + o2 → 2h2o
never [62]

An exothermic reaction is one which is accompanied by the release of heat energy.

In the given situation, hydrogen and oxygen combine to form water along with the generation of heat.

2H2 + O2 → 2H2O + heat

Based on the law of conservation of energy: 'energy can be neither created nor destroyed". This implies that whatever energy is released must have been present in the reactants. Therefore, the reactants must be in a higher energy level than products.

If the reaction shown below is exothermic, the energy level of the reactants is higher than products.


5 0
2 years ago
Convert 1.21 kg to grams
MissTica

Answer:

1210 grams

Explanation:

Message me for extra info.

snap- parkguy786

7 0
2 years ago
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sergij07 [2.7K]
Concentration\ rate=\frac{mass\ of\ product}{mass\ of\ substance}*100\%\\\\&#10;15\%=\frac{m_1}{ms_1}*100\%\\ms_1=10pints\\&#10;15\%=\frac{m_1}{10}*100\%\\&#10;\frac{15}{100}=\frac{m_1}{10}\ \ |*10\\&#10;m_1=\frac{150}{100}=1,5pints\\\\&#10;10\%=\frac{m_2}{15}*100\%\\&#10;0,1=\frac{m_2}{15}\ \ |*15\\&#10;1,5=m_2\\&#10;Resulting\ solution:\\&#10;ms=ms_1+ms_2=15+10=25pints\\m=m_1+m_2=1,5+1,5=3pints&#10;\\\frac{m}{ms}*100\%=\frac{3}{25}*100\%=12\%
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2 years ago
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