answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
AlladinOne [14]
2 years ago
15

The insecticide DDT has a half-life in the human body of approximately 7 years. [In 7 years its concentration decreases to half

its initial concentration). Although DDT is no longer used in the United States, 25 years ago that average farmer had a body DDT concentration of 22ppm [parts per million by weight). Estimate what the farm workers present concentration is?
Chemistry
1 answer:
iragen [17]2 years ago
3 0

Answer:

explanation below

Explanation:

Dichlorodiphenyltrichloroethane, also known as DDT is a chemical compound that is found in insecticides. In 1972, the United States Environmental Protection Agency issued an order for the cancellation of requests for the chemical compound because it affects wildlife and pose risks to humans as well.  

From the question here, it was noted that the initial concentration was 22ppm 25years ago and so if it takes 7years to decay by half, the actual concentration in present day farmers could be calculated as follows;

25years ago  - 22ppm

18years ago  - 11ppm

11years ago – 5.5 ppm

4 years ago -  2.75ppm

Since 7yrs = 0.5

Then 4yrs will be [ [4/7] x 0.5] = 0.2857

Then if 0.5 = 2,

Then 0.2857 = [ [ 0.2857/0.5] x 2] = 1.1428

So present year concentration would then be [2.75ppm/1.1428] = 2.406ppm

You might be interested in
Determine the empirical formula for compounds that have the following analyses: a. 66.0% barium and 34.0% chlorine b. 80.38% bis
almond37 [142]

Answer: a) BaCl_2

b)  BiO_3H_3

Explanation:

If percentage are given then we are taking total mass is 100 grams.

So, the mass of each element is equal to the percentage given.

a) Mass of Ba= 66.06 g

Mass of Cl = 34.0 g

Step 1 : convert given masses into moles.

Moles of Ba =\frac{\text{ given mass of ba}}{\text{ molar mass of Ba}}= \frac{66.06g}{137g/mole}=0.48moles

Moles of Cl = \frac{\text{ given mass of Cl}}{\text{ molar mass of Cl}}= \frac{34g}{35.5g/mole}=0.96moles[/tex]

Step 2 : For the mole ratio, divide each value of moles by the smallest number of moles calculated.

For Ba = \frac{0.48}{0.48}=1

For O =\frac{0.96}{0.48}=2

The ratio of Ba: Cl= 1:2

Hence the empirical formula is BaCl_2

b) Mass of Bi= 80.38 g

Mass of O= 18.46 g

Mass of H = 1.16 g

Step 1 : convert given masses into moles.

Moles of Bi =\frac{\text{ given mass of ba}}{\text{ molar mass of Ba}}= \frac{80.38g}{209g/mole}=0.38moles

Moles of O= \frac{\text{ given mass of O}}{\text{ molar mass of O}}= \frac{18.46g}{16g/mole}=1.15moles

Moles of H=\frac{\text{ given mass of H}}{\text{ molar mass of H}}= \frac{1.16g}{1g/mole}=1.16moles

Step 2 : For the mole ratio, divide each value of moles by the smallest number of moles calculated.

For Bi= \frac{0.38}{0.38}=1

For O =\frac{1.15}{0.38}=3

For H=\frac{1.16}{0.38}=3

The ratio of Bi: O: H= 1:3: 3

Hence the empirical formula is BiO_3H_3

6 0
2 years ago
Two atoms bonded together will remain some distance apart, minimizing the Question 1 options: A) potential energy of the bond. B
Taya2010 [7]

Answer:

1) potential energy of the bond.

2) Linear

3) The electrons are transferred from K to Cl.

4) ClF

5) Oxygen

6) Electrolysis

7) Double displacement

Explanation:

As two atoms approach each other in a bonding situation, the potential energy of the bond is minimized as the internuclear distance of the bonding atoms decreases.

BeH2 has two electron domains and the central beryllium atom is sp2 hybridized. According to valence shell electron pair repulsion theory. A molecule having two regions of electron density will lead to a linear molecule.

KCl is an ionic compound hence there is a transfer of electrons from K(metal) to Cl(nonmetal).

ClF has partial charges because it contains a polar covalent bond. The partial charges arise from the dipole within the molecule. LiF is a pure ionic compound formed by transfer of electrons from Li to F. The species possess full and not partial charges.

When an oxygen atom bonds with another oxygen atom, what has been formed is a homonuclear covalent bond. Since the electro negativity of the both atoms is exactly the same, a pure covalent bond is formed. Recall that polar covalent bonds are formed when there is a significant electro negativity difference between the bonding atoms.

When direct current is passed through certain salt solutions during electrolysis, gases may be evolved and collected at the appropriate electrodes.

A double-replacement reaction is a reaction in which the cations and anions present in two different ionic compounds that are reacting together exchange their positions to form two new compounds on the product side. For instance, look at the reaction shown in question 7 as a typical example of this;

AgNO3 (s) + NaCl (s) → AgCl (s) + NaNO3 (s).

8 0
2 years ago
Room temperature is about 20 degrees Celsius. Explain how you could convert this temperature to kelvin. Use evidence from the fi
Taya2010 [7]

Answer:

293.15 K.

Explanation:

It is given that, the room temperature is 20 degrees Celsius.

We need to convert this temperature into kelvin.

The conversion from degrees Celsius to Kelvin is as follows :

T_k=T_c+273.15

We have, T_c=20^{\circ} C

So,

T_k=20+273.15\\\\T_k=293.15\ K

So, the room temperature is 293.15 kelvin.

8 0
2 years ago
Chloe wants to lighten the color of her dark hair, which will require the use of both haircolor and hydrogen peroxide. hydrogen
bearhunter [10]

The answer is developer .

Chloe wants to lighten the color of her dark hair, which will require the use of both hair color and hydrogen peroxide.

Hydrogen peroxide (H₂O₂) is an example of a most commonly used developer in hair color.

Hydrogen peroxide lighten hair color, as it can dissolve darker pigment. According to the  natural hair color and the length of time a person will leave hydrogen peroxide on  hair,  hair can turn somewhere on the color spectrum between caramel, orange and yellow.





7 0
2 years ago
A 60.0 mL solution of 0.112 M sulfurous acid (H2SO3) is titrated with 0.112 M NaOH. The pKa values of sulfurous acid are 1.857 (
djverab [1.8K]

Answer:

a)4.51

b) 9.96

Explanation:

Given:

NaOH = 0.112M

H2S03 = 0.112 M

V = 60 ml

H2S03 pKa1= 1.857

pKa2 = 7.172

a) to calculate pH at first equivalence point, we calculate the pH between pKa1 and pKa2 as it is in between.

Therefore, the half points will also be the middle point.

Solving, we have:

pH = (½)* pKa1 + pKa2

pH = (½) * (1.857 + 7.172)

= 4.51

Thus, pH at first equivalence point is 4.51

b) pH at second equivalence point:

We already know there is a presence of SO3-2, and it ionizes to form

SO3-2 + H2O <>HSO3- + OH-

Kb = \frac{[ HSO3-][0H-]}{SO3-2}

Kb = \frac{10^-^1^4}{10^-^7^.^1^7^2} = 1.49*10^-^7

[HSO3-] = x = [OH-]

mmol of SO3-2 = MV

= 0.112 * 60 = 6.72

We need to find the V of NaOh,

V of NaOh = (2 * mmol)/M

= (2 * 6.72)/0.122

= 120ml

For total V in equivalence point, we have:

60ml + 120ml = 180ml

[S03-2] = 6.72/120

= 0.056 M

Substituting for values gotten in the equation Kb=\frac{[HSO3-][OH-]}{[SO3-2]}

We noe have:

1.485*10^-^7=\frac{x*x}{(0.056-x)}

x = [OH-] = 9.11*10^-^5

pOH = -log(OH) = -log(9.11*10^-^5)

=4.04

pH = 14- pOH

= 14 - 4.04

= 9.96

The pH at second equivalence point is 9.96

4 0
2 years ago
Other questions:
  • Relate text and visuals using the cartoon, explain why the potassium atom becomes positively charged and the fluorine atom becom
    8·1 answer
  • When Xavier places his hands near a light bulb, he notices that certain areas around the light bulb are warmer than others. Whic
    13·2 answers
  • A person is standing on ice. He throws a snowball with a force of 4 N to the right, while the snowball pushes the person with a
    14·2 answers
  • What fact do scientists believe provides evidence for the big bang theory?a. all comets follow elliptical orbits.b. most extra-s
    10·2 answers
  • The decomposition of copper(II) nitrate on heating is endothermic reaction. 2Cu(NO3)2(s) → 2C10(s) + 4NO2(g) + O2(g) Calculate t
    12·1 answer
  • In the 1980s, there was an international agreement to destroy all stockpiles of mustard gas, ClCH2CH2SCH2CH2Cl. When this substa
    5·1 answer
  • Match the specific enzyme to its class. A. oxidoreductase B. hydrolase C. transferase D. ligase E. lyase aminase
    8·1 answer
  • A liquid mixture containing 30.0 mole% benzene (B), 25.0% toluene (T), and the balance xylene (X) is fed to a distillation colum
    13·1 answer
  • A student requires 2.00 L of 0.100 M NH4NO3 from a 1.75 M NH4NO3 stock solution. What is the correct way to get the solution?
    11·2 answers
  • Nicole has 2 glasses on the counter: one of water and one of sugar. She is baking a cake and needs to use the sugar-water for th
    11·2 answers
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!