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Oliga [24]
3 years ago
10

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

Chemistry
1 answer:
weqwewe [10]3 years ago
8 0

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

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Answer:

0.725 kg

Explanation:

Step 1: Given data

  • Kinetic energy of the softball (K): 145 J
  • Speed of the softball (v): 20.0 m/s
  • Mass of the softball (m): ?

Step 2: Calculate the mass of the softball

We will use the following expression.

K = 1/2 × m × v²

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m = 0.725 kg

The mass of the softball is 0.725 kg.

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What kind of plant growth hormone to regular plant growth. We dissolve 5.0 mg of the solution into 2.0 kg of water. What is the
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Answer:

The dosage of the solution is 2.5 parts per million.

Explanation:

The solvent proportion in parts per million is equal to the ratio of solution in miligrams to ratio of water in miligrams multiplied by a million. (A kilogram is equivalent to a million miligrams) That is:

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1. What is an isomer? How many possible isomers of hexane are there? What are the structural differences between these isomers?
VARVARA [1.3K]
Answer 1:
Isomers are compounds with same molecular formula but different structure formula. Isomers are classified into two types
a) Structural/configurational isomers
b) Stereo isomers
In structural/configurational isomers  atom and functional groups are attached in different fashion. Structural isomers may have different functional groups. Structural isomers are further classified as chain isomers, position isomers and functional isomers. In case of stereo-isomers, compounds have same functional group, but different orientation in space. They also have difference activity towards polarized light.

 Answer 2:
Hexane has a molecular formula of C6H14. It exhibits following structural isomers
a) hexane<span>,
b) 2-methylpentane
c)3-methylpentane
d) 2,2-dimethylbutane
e) 2,3-dimethylbutane
Thus, in all there are 5 isomers of hexane

Answer 3: 
</span><span>Butane has two possible isomers but that decane has 75 possible isomers. This can be attributed to the fact that butane has 4 carbon atoms, while decane has 10 carbon atom. As the number of carbon atom increases, there are higher possible sites of linkage, in different fashion. Therefore, as number 69 of carbon atoms increases, number of different possible isomers increases. 

Answer 4:
It has been observed that, though isomers have same molecular formula, but the have different boiling points. Infact, branched isomers have lower boiling point as compared to linear isomers. For example, hexane has boiling point = 69 oC, 2 methyl pentane has boiling point = 60 oC, 2,4, dimethyl butane has boiling point = 58 oC and 2,2 dimethyl butane has boiling point = 50 oC. Thus, it can be observed that branched isomers have lower boiling points as compared to linear isomers. This can be attributed to lower van der Waal's forces of interaction in branched isomers as compared to linear isomers. 
</span><span>
</span>
5 0
2 years ago
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