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Leviafan [203]
3 years ago
6

Plsss help me!!! ASAP!!!

Chemistry
1 answer:
Arisa [49]3 years ago
8 0

Answer:

I think the answer is D...

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How long will it take for a 750 mg sample of radium with a half life of 15 days to decay to exactly 68mg?
weqwewe [10]

Answer:

52 da  

Step-by-step explanation:

Whenever a question asks you, "How long to reach a certain concentration?" or something similar, you must use the appropriate integrated rate law expression.

The i<em>ntegrated rate law for a first-order reaction </em>is  

ln([A₀]/[A] ) = kt

Data:

[A]₀ = 750 mg

 [A] =    68 mg

t_ ½ =   15 da

Step 1. Calculate the value of the rate constant.

 t_½ = ln2/k     Multiply each side by k

kt_½ = ln2         Divide each side by t_½

      k = ln2/t_½

         = ln2/15

         = 0.0462 da⁻¹

Step 2. Calculate the time

ln(750/68) = 0.0462t

         ln11.0 = 0.0462t

            2.40 = 0.0462t     Divide each side by 0.0462

                   t = 52 da

8 0
3 years ago
What is the molality of sodium chloride in solution that is 13.0% by mass sodium chloride and that has a density of 1.10 g/ml?
8090 [49]
Answer is: molality od sodium chloride is 2,55 mol/kg.
V(solution) = 100 ml.
m(solution) = d(solution) · V(solution).
m(solution) = 1,10 g/ml · 100 ml.
m(solution) = 110 g.
ω(NaCl) = 13,0% = 0,13.
m(NaCl) = ω(NaCl) · m(solution).
m(NaCl) = 0,13 · 110 g.
m(NaCl) = 14,3 g.
n(NaCl) = m(NaCl) ÷ M(NaCl).
n(NaCl) = 14,3 g ÷ 58,5 g/mol.
n(NaCl) = 0,244 mol.
m(H₂O) = 110 g - 14,3 g.
m(H₂O) = 95,7 g = 0,0957 kg.
b(NaCl) = n(NaCl) ÷ m(H₂O).
b(NaCl) = 0,244 mol ÷ 0,0957 kg.
b(NaCl) = 2,55 mol/kg.
3 0
3 years ago
Do cells divide twice in asexual reproduction, sexual reproduction, or both?
igor_vitrenko [27]
Cells divide in asexual reproduction!


I hope this helps 



please mark me as brainliestt!!
8 0
3 years ago
0.01040 m as an integer
SpyIntel [72]

Answer:

Here,

0.01040 m as an integer= 1.04 × 10-2

5 0
2 years ago
a gas chamber is filled with four gases. When a small opening is made in the gas chamber you expect which gas to escape last hyd
Nimfa-mama [501]
I really don’t know the answer, please help this kiddo with his question
8 0
2 years ago
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