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Leya [2.2K]
3 years ago
14

DDT was once considered a "silver bullet" that would permanently eradicate insect pests. Today, instead, DDT is largely useless

against many insects. Which of these would have been required for this pest eradication effort to be successful in the long run? A) Larger doses of DDT should have been applied. B) All habitats should have received applications of DDT at about the same time. C) The frequency of DDT application should have been higher. D) None of the individual insects should have possessed genomes that made them resistant to DDT. E) DDT application should have been continual.
Chemistry
1 answer:
Scorpion4ik [409]3 years ago
4 0

Answer:  the correct answer is D) None of the individual insects should have possessed genomes that made them resistant to DDT.

Explanation: the problem is that DDT has become ineffective because insects have become more resistant to DDT.

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If 27.3% of a sample of silver-112 decays in 1.52 hours, what is the half-life (in hours to 3 decimal places)?
ICE Princess25 [194]

<u>Answer:</u> The half life of the sample of silver-112 is 3.303 hours.

<u>Explanation:</u>

All radioactive decay processes undergoes first order reaction.

To calculate the rate constant for first order reaction, we use the integrated rate law equation for first order, which is:

k=\frac{2.303}{t}\log \frac{[A_o]}{[A]}

where,

k = rate constant = ?

t = time taken = 1.52 hrs

[A_o] = Initial concentration of reactant = 100 g

[A] = Concentration of reactant left after time 't' = [100 - 27.3] = 72.7 g

Putting values in above equation, we get:

k=\frac{2.303}{1.52hrs}\log \frac{100}{72.7}\\\\k= 0.2098hr^{-1}

To calculate the half life period of first order reaction, we use the equation:

t_{1/2}=\frac{0.693}{k}

where,

t_{1/2} = half life period of first order reaction = ?

k = rate constant = 0.2098hr^{-1}

Putting values in above equation, we get:

t_{1/2}=\frac{0.693}{0.2098hr^{-1}}\\\\t_{1/2}=3.303hrs

Hence, the half life of the sample of silver-112 is 3.303 hours.

6 0
3 years ago
What is the mass number of an atom?
Gennadij [26K]
The mass number of an atom is its total number of protons and neutrons. Atoms of different elements usually have different mass numbers , but they can be the same. For example, the mass number of argon atoms and calcium atoms can both be 40.
3 0
3 years ago
Read 2 more answers
Which products result from the process of photosynthesis? Check all that apply.
SashulF [63]
The answer is carbon dioxide
3 0
4 years ago
Read 2 more answers
The diagrams below represent the four states of matter.
UkoKoshka [18]
Diagram 1 exhibits the nature of the particles within the state that forms after a solid melts. Solids melt into liquids and the particles within a liquid have a greater spacing than the particles in a solid. Moreover, these particles are free to slip over one another, which means that liquids do not have a definite shape; however, the particles are still confined in by intermolecular forces, which means that the volume of a liquid is definite.
6 0
3 years ago
Read 2 more answers
What is the specific heat capacity of silver metal if 55.00 g of the metal absorbs 193.9J of heat and the temperature rises 15.0
skad [1K]

Answer:

The specific heat capacity of silver is 0.24 j/g.°C.

Explanation:

Given data:

Mass of sample = 55.00 g

increase of temperature ΔT= 15.0 °C

Heat absorbed = 193.9 J

Specific heat capacity of silver = ?

Solution:

Specific heat capacity:

It is the amount of heat required to raise the temperature of one gram of substance by one degree.

Formula:

Q = m.c. ΔT

Q = amount of heat absorbed or released

m = mass of given substance

c = specific heat capacity of substance.

ΔT = change in temperature

Now we will put the values in formula.

193.9 J = 55.00 g × c ×15.0 °C

193.9 J = 825 g.°C  × c

c = 193.9 J / 825  g.°C

c= 0.24 /g.°C

The specific heat capacity of silver is 0.24 j/g.°C.

5 0
3 years ago
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