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Salsk061 [2.6K]
2 years ago
12

An isotope has a half-life of 10 minutes. after 20 minutes, what percentage of the original nuclei remain?

Chemistry
1 answer:
Elena-2011 [213]2 years ago
6 0
To solve this, we can use two equations.
t1/2 = ln 2 / λ = 0.693 / λ  
   
where, t1/2 is half-life and λ is the decay constant.

t1/2 = 10 min = 0.693 / λ

Hence, λ = 0.693 / 10 min              -         (1)

Nt = Nο e∧(-λt)    
                
Nt = amount of atoms at t =t time
Nο= initial amount of atoms
t = time taken

by rearranging the equation,
Nt/Nο = e∧(-λt)                  -  (2)

From (1) and (2),

Nt/Nο = e∧(-(0.693 / 10 min) x 20 min) 
Nt/Nο = 0.2500

Percentage of remaining nuclei = (nuclei at t time / initial nuclei) x 100%
                                                     
= (Nt/Nο ) x 100%
                                                      = 0.2500 x 100%
                                                      = 25.00%

Hence, Percentage of remaining nuclei is 25.00%
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5 0
3 years ago
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The combustion method used to analyze for carbon and hydrogen can be adapted to give percentage N by collecting the nitrogen fro
12345 [234]

Answer:

The percentage of N in the compound is 0.5088

Explanation:

Mass of compound = 8.75 mg = 8.75×1000 = 8750 g

Mass of N2 = number of moles of N2 × MW of N2 = 1.59 × 28 = 44.52 g

% of N in the compound = (mass of N2/mass of compound) × 100 = (44.52/8750) × 100 = 5.088×10^-3 × 100 = 0.5088

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3 years ago
A moist red litmus paper is used for testing ammonia gas ,why​
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when the red litmus paper is placed in a jar of ammonia, the red litmus paper turns into blue as ammonia gas is basic in nature. It confirms the alkalinity of the ammonia gas.

6 0
2 years ago
Porquê que o potássio é mais reativo que o cálcio? urgente!
saul85 [17]

Answer: O potássio possui apenas um elétron de valência. ... Considerando que o cálcio possui dois elétrons de valência, requer mais energia para a remoção de um elétron de valência. Devido a esse potássio, é mais reativo que o cálcio.

Explanation:

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3 years ago
What are the molality and mole fraction of solute in a 22.3 percent by mass aqueous solution of formic acid (HCOOH)?
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Answer:

Mole fraction for solute = 0.1, or 10%

Molality = 6.24 mol/kg

Explanation:

22.3% by mass → In 100 g of solution, we have  22.3 g of HCOOH

Mass of solution = 100 g

Mass of solute = 22.3 g

Mass of solvent = 100 g - 22.3g = 77.7 g

Let's convert the mass to moles

22.3 g . 1mol/ 46 g = 0.485 moles

77.7 g. 1mol / 18 g = 4.32 moles

Total moles = 4.32 moles + 0.485 moles = 4.805 moles

Xm for solute = 0.485 / 4.805 = 0.100 → 10%

Molality → mol/ kg → we convert the mass of solvent to kg

77.7 g.  1 kg / 1000g = 0.0777 kg

0.485 mol / 0.0777 kg = 6.24 m

6 0
3 years ago
Read 2 more answers
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