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dimaraw [331]
3 years ago
7

If you start with 100 grams of a radionuclide, how much will you have after two half-lives have passed?

Chemistry
2 answers:
Contact [7]3 years ago
8 0
After first half-life you will have 100/2=50g. After second half-life you will have 50/2=25g.
zubka84 [21]3 years ago
6 0
25 grams. 

A half life is the amount of time it takes for an isotope to decay half of itself. 

So after one half life, there will be half of the original amount. 

100/2=50

After another half life, there will be half of that amount. 

50/2 = 25
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At 400 k, the equilibrium constant for the reaction is kc = 7.0. br2 (g) + cl2 (g) 2brcl (g) a closed vessel at 400 k is charged
jeka57 [31]
a) when Kc = concentration of products / concentration of reactants
  So according  to the reaction equation:
Br2(g) + Cl2(g) → 2BrCl(g)

∴ Kc =[BrCl] ^2 / [Br2][Cl2]

b) when q = [BrCl]^2 / [Br2][Cl2]
and we have [BrCl] = 3 m 
[Br2] = 1 m 
[Cl2] = 1 m
So by substitution:
q= 3^2 / 1*1 = 9 

- and we can see that q > Kc 
the reaction is not at equilibrium that means there are more products and the reaction shifts to the left to increase the reactants and decrease the products to achieve equilibrium.

C) by using ICE table:

              Br2(g) + Cl2(g) → 2BrCl (g)
initial       1               1               3
change  -X              -X            +X
Equ       (1-X)          (1-X)         (3+X)

when Kc = [Brcl]^2/[Cl2][Br2]
by substitution:
7 = (3+X)^2 / (1+X) (1+X)  by solving this equation for X
∴X = 0.215
so at equilibrium:
∴ [Br2] = [Cl2] = 1-0.215 = 0.785 m 
    [BrCl] = 3+0.215 = 3.215 m
4 0
3 years ago
Calculate the mass in grams of 8.35 × 1022 molecules of CBr4.
antiseptic1488 [7]

Answer: 45.983 g CBr₄

Explanation:

To convert from moles to grams, you know that we will need molar mass and Avogadro's number.

Avogadro's number: 6.022×10²³ molecules/mol

Molar mass: 331.627 grams/mol

Now that we have what we need, you can use these to solve for grams. 8.35*10^2^2molecules CBr_{4} *\frac{1mol}{6.022*10^2^3molecules} *\frac{331.627 g}{1 mol} =45.983 g

Our final answer is 45.983 g CBr₄.

4 0
3 years ago
The first-order rate constant for the decomposition of N2O5:
kifflom [539]

Answer:

0.0055 mol of N2O5 will remay after 7 min.

Explanation:

The reaction follows a first-order.

Let the concentration of N2O5 after 7 min be y

Rate = Ky = change in concentration of N2O5/time

K is rate constant = 6.82×10^-3 s^-1

Initial concentration of N2O5 = number of moles/volume = 2.1×10^-2/1.8 = 0.0117 M

Change in concentration = 0.0117 - y

Time = 7 min = 7×60 = 420 s

6.82×10^-3y = 0.0117 - y/420

0.0117 - y = 420×6.82×10^-3y

0.0117 - y = 2.8644y

0.0117 = 2.8644y + y

0.0117 = 3.8644y

y = 0.0117/3.8644 = 0.00303 M

Number of moles of N2O5 left = y × volume = 0.00303 × 1.8 = 0.0055 mol (to 2 significant digits)

5 0
3 years ago
What is the valence electron configuration for the oxygen atom
Lana71 [14]
Oxygen has six valence (outer-shell) electrons so therefore gains two more electrons to form the O-2 ion Its electron configuration is: 1s2 2s2 2p6 or Ne

If this helped mark Brainliest!
8 0
3 years ago
How many hydrogen atoms are attached to each carbon adjacent to a double bond? nurition?
larisa [96]
That depends. there are 2 possible answers.
      H
C - C = C - H gives a different answer on the right than on the left.

One the left side, the second Carbon is attached to a double bond and has but one hydrogen attached to it.

The Carbon on the right of the double bond has 2
     H
C- C = C - H
            H

I'm not sure what you should put. It's one of those things that I would repeat my argument and submit it.
3 0
3 years ago
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