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-Dominant- [34]
3 years ago
10

Pls help fast test due soon!

Chemistry
1 answer:
baherus [9]3 years ago
7 0

Answer:

atom

Explanation:

the correct answer is atom

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An isotope has a half-life of 10 minutes. after 20 minutes, what percentage of the original nuclei remain?
Elena-2011 [213]
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%
6 0
3 years ago
Answer my my science homework please
ludmilkaskok [199]
1. D

2. <span>83.5 million years ago - 66 million years ago

3. </span><span>It had armor and could rotate to keep its caudal bludgeon facing the enemy.

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5 0
3 years ago
10) In order to make spaghetti cook faster, a chef adds salt to water. How many moles of salt would he need to add to 1.0 kg wat
Vadim26 [7]
The answer is 4.9 moles.
Solution: 
Using the equation for boiling point elevation Δt,
     Δt = i Kb m 
we can rearrange the expression to solve for the molality m of the solution:
     m = Δt / i Kb 

Since we know that pure water boils at 100 °C, and the Ebullioscopic constant Kb for water is 0.512 °C·kg/mol, 
     m = (105°C - 100°C) / (2 * 0.512 °C·kg/mol)
         = 4.883 mol/kg 

From the molality m of the solution of salt added in a kilogram of water, we can now find the number of moles of salt: 
     m = number of moles / 1.0kg
     number of moles = m*1.0kg 
                                  = (4.883 mol/kg) * (1.0kg)
                                  = 4.9 moles
4 0
3 years ago
Aqueous sulfuric acid reacts with solid sodium hydroxide to produce aqueous sodium sulfate and liquid water . If of sodium sulfa
notka56 [123]

Answer:

27%

Explanation:

Hello,

The following information is missing, but I found it: "1.92 g of sodium sulfate is produced from the reaction of 4.9 g of sulfuric acid and 7.8 g of sodium hydroxide" so the undergoing chemical reaction is:

2NaOH+H_2SO_4-->Na_2SO_4+2H_2O

Now, to compute the percent yield, we must first establish the limiting reagent to subsequently determine the theoretical yield of sodium sulfate because the real (1.92g) is already given, thus, we consider the following procedure:

n_{NaOH}=7.8gNaOH*\frac{1molNaOH}{40gNaOH}=0.2molNaOH\\n_{H_2SO_4}=4.9gH_2SO_4*\frac{1molH_2SO_4}{98gH_2SO_4}=0.050molH_2SO_4\\

- The moles of sodium hydroxide that completely react with 0.05 moles of sulfuric acid are:

0.2molNaOH*\frac{1molH_2SO_4}{2molNaOH}=0.098molH_2SO_4

As this number is higher than the previously computed 0.05 moles of available sulfuric acid, one states that the sulfuric acid is the limiting reagent. Now, the theoretical grams of sodium sulfate are found via:

0.05molH_2SO_4*\frac{1molNa_2SO_4}{1mol H_2SO_4} *\frac{142.04gNa_2SO_4}{1molNa_2SO_4} =7.1gNa_2SO_4

Finally, the percent yield turns out into:

Y=\frac{1.92g}{7.1g} *100

Y=27.0%

Best regards.

6 0
3 years ago
Which statement compares the masses of two subatomic particles?
Nataly [62]
<span>The mass of a proton is greater than the mass of an electron.</span>
6 0
3 years ago
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