it has been found that ddt in the soil decomposes by a first-order reaction with a half-life of 12.0 years. how long would it take ddt in a soil sample to decompose from a concentration of 195 ppbm (parts per billion by mass) to 15 ppbm?

The percent yield of the reaction with formation of lead oxide  is 70.29%.

Percent yield is defined as the ratio of actual yield to the theoretical yield multiplied by 100. If the actual and theoretical yield are same then the percent yield is 100%.If actual yield is less than the theoretical yield then the percent yield is less than 100%.Reason of this condition arising is the incompletion of reaction or loss of sample during recovery process.

In cases where percent yield is over 100% it indicates that more sample is recovered than the predicted amount.This condition arises when there are other simultaneous reactions taking place leading to the formation of product. It can also arise if there is incomplete removal of impurities from the sample .

In the given problem, 2 moles of lead produce 2 moles of lead oxide

That is, 414.4 g lead produces 446.4 g of lead oxide

hence,451.54 g lead will produce 451.4×446.4/414.4=486.251 g which is the theoretical yield

Now by substituting the values in the formula,341.8/486.251 ×100=70.29%

Hence, the percent yield of the reaction is 70.29%.

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Both transition metals and alkali metals are good conductors of heat and electricity, react with water, and are easily oxidized.

The alkali metals are elements of group 1 which are lithium (Li), sodium (Na), potassium (K), rubidium (Rb), caesium (Cs), and francium (Fr).  They are also known as the s-block elements because they have their outermost electron in an s-orbital.

The alkali metals are shiny, soft, highly reactive metals and readily lose their outermost electron to create cations with charge +1. They can tarnish rapidly in the air due to oxidation by atmospheric moisture and oxygen.

Transition elements or transition metals are elements that have partially filled d-orbitals. An element having a d-subshell that is partially filled with electrons or can form stable cations with an incompletely filled d orbital.

Any element present in the d-block of the modern periodic table which consists of groups 3 to 12, is considered to be a transition element. For example, the mercury in the +2 oxidation state, corresponds to an electronic configuration of (n-1)d¹⁰. Many paramagnetic compounds are formed by transition metals because they have unpaired electrons in the d orbital.

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Answer:

For addition and subtraction use the following rules:

1. Count the number of significant figures in the decimal portion ONLY of each number in the problem

2. Add or subtract in the normal fashion

3. Your final answer may have no more significant figures to the right of the decimal than the LEAST number of significant figures in any number in the problem.

Explanation:

Consider a 3-atom molecule a-b-a for which b has a total of only two valence electrons if you assume that b is a group ii metal, then the bond angle for a-b-a is 180 degree

Valence electron is the s and p electron in the outermost shell and electron present in the inner shell are core electron and according to the valence shell electron pair repulsion theory and we that bond angle that an atom has with its neighbor which also called dihedral angle a group II metal has two valence electron there it can form only single bond then b will not have any lone pair and the ones digit in the group number is the number of valence electron and 180 degree bond angle means the atom are connected in straight line called 180 degree bond

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Answer: True

Explanation: Synthetic materials are not found in nature and can be created in labs using chemicals and compounds.

Answer:

use a tumbler to cover a candle that is burning, after a few minutes it turns off automatically without any external forces due to the absence of oxygen

Explanation:

A covalent bond bond is appropriately described as occurring when one or even more electrons move of one atom to another.

a bond in which the two bound atoms' electron densities are unequally distributed as a result of either a difference in the electronegativity or the effects of induction.

A covalently bonded bond is represented by the water molecule, written as H2O. The oxygen atom is given more time with the electrons than for hydrogen atoms due to the unequal distribution of the electrons.

The electron is an unit of matter with a negative zero elementary charge electric charge. Due to their lack of known components, electrons, which are part of the first generation of lepton particles family, are typically regarded to be elementary particles or substructure

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The heat released by metal and added to water is the same which is 1039.83 joule.

The equilibrium condition of the system depends on the heat released from both gold and water. The total heat received by the system will equal to total heat released by objects. It should follow

Q released = Q received

The heat can be defined by

Q = m . c . ΔT

where Q is heat, m is mass, c is the specific heat constant and ΔT is the change in temperature.

The given parameters are

m = 17.27 g = 0.01727 kf

T1 = 92 ⁰C

T2 = 25.1 ⁰C

c = 900 J/kg⁰C

By substituting the given parameters, we can calculate the heat

Q = m . c . ΔT

Q = 0.01727 . 900 . (92 - 25.1)

Q = 1039.83 joule

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As per the chemical reaction ,sodium hydroxide can be used for neutralization of sulfuric acid as,2 NaOH+H₂SO₄[tex]\rightarrow[/tex]Na₂SO₄ +2 H₂O.

Chemical reactions are defined as reactions which occur when a substance combines with another substance to form a new substance.Alternatively, when a substance breaks down or decomposes to give new substances it is also considered to be a chemical reaction.

There are several characteristics of chemical reactions like change in color, change in state , change in odor and change in composition . During chemical reaction there is also formation of precipitate an insoluble mass of substance or even evolution of gases.

There are three types of chemical reactions:

1) inorganic reactions

2)organic reactions

3) biochemical reactions

During chemical reactions atoms are rearranged and changes are accompanied by an energy change as new substances are formed.

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The experiment should be conducted by Jane for several days and the observation of each light and its effect on the plant buds should be noted carefully.

To conduct this experiment, first, place a flowering plant in a place that receives that receive optimum sunlight. This is because this experiment is to be conducted at night time to observe the changes in the bud.

The plant should be watered and at the night, the plant should be placed under a colored light say let us take the blue colored light for the first week. The structure and shape of the bud should be noted in the initial time while placing the colored light after sunset and it should be noted before sunrise.

This observation should be noted for a week. For consecutive weeks, the colors of the light should be changed and the same observations are to be noted.

Later, from the observations inferred, the conclusion could be obtained if the plant and its bud have any effect on exposure to colored lights for several weeks.

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Alanine is a member of the twenty key amino acids which might be used by our bodies to make proteins: Pyrrolysine (not utilized in human protein synthesis). of those 20 amino acids, nine amino acids are crucial: Phenylalanine. Valine. Tryptophan.

Alanine is an amino acid that is used to make proteins. it's miles used to break down tryptophan and diet B-6. it's miles a source of power for muscle mass and the central fearful gadget. It strengthens the immune device and helps the frame use sugars.

Alanine, or α-alanine, is an α-amino acid this is used in the biosynthesis of proteins. It contains an amine organization and a carboxylic acid organization, both connected to the valuable carbon atom which also contains a methyl institution facet chain. Alanine is an amino acid this is used to make proteins. it's miles used to interrupt down tryptophan and diet B-6. it's miles a supply of electricity for muscle tissue and the critical apprehensive gadget. It strengthens the immune system and allows the frame to use sugars.

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Volume of 16.0 m aqueous ammonia solution required to prepare 500.0 ml of a 1.90 m solution is 50ml

Molarity is used to describe the concentration of a solution. Molarity, also called molarity, is the number of moles of solute (dissolved substance) per liter of solution. The unit of molarity is moles per cubic decimeter, written as mol dm⁻³ or simply M. A cubic decimeter is the same as a liter. In many old textbooks you can find concentrations in moles/liter written as mol l⁻¹

Original concentration x initial volume = final concentration x final volume.

We will use the equation (M₁)(V₁) = (M₂)(V₂)

Given,

M₁ = 16.0 m

M₂ = 1.90 m

V₂ = 500.0 ml or 0.5L

So, 16 × V₁ = 1.90 ×  0.5

16 V₁ = 0.9 m

V₁ = [tex]\frac{0.9}{16}[/tex]

V₁ = 0.05L or 50ml

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Answer:

So, liquid H2 will be distilled first, after this liquid N2 will be distilled, followed by liquid O2 and liquid CO2 will be distilled last.

The compound will lower molecular weight will distill out first as it will evaporate fast.

Compound is defined as a chemical substance made up of identical molecules containing atoms from more than one type of chemical element.

Molecule consisting atoms of only one element is not called compound.It is transformed into new substances during chemical reactions. There are four major types of compounds depending on chemical bonding present in them.They are:

1)Molecular compounds where in atoms are joined by covalent bonds.

2) ionic compounds where atoms are joined by ionic bond.

3)Inter-metallic compounds where atoms are held by metallic bonds

4) co-ordination complexes where atoms are held by co-ordinate bonds.

They have a unique chemical structure held together by chemical bonds Compounds have different properties as those of elements because when a compound is formed the properties of the substance are totally altered.

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Photochemical smog is  formed from nitrogen oxides.

When the sun's ultraviolet rays interact with the atmosphere's nitrogen oxides, photochemical smog is created. It appears as a brown haze and is most noticeable in the morning and late afternoon, particularly in warm, densely populated places.

Although the formation of photochemical haze is a complicated process, its origin is relatively clear. While coal-fired power plants and some other power plants also produce the required pollutants to permit its manufacturing, automobiles are the main contributor.

Therefore, Photochemical smog is  formed from nitrogen oxides.

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The photochemical smog is formed from nitrogen oxides. Thus option D is correct.

Photochemical smog is defined as a combination of pollutants that are produced when sunlight interacts with nitrogen oxides and volatile organic compounds (VOCs), resulting in a brown haze above cities.

It is also defined as a brownish-gray haze brought on by the sun's UV rays reacting with the atmosphere's hydrocarbon and nitrogen oxide pollution.

When volatile organic molecules and nitrogen oxides interact with sunlight, photochemical smog is formed, which is comparable to a mixture of contaminants.

Thus, the photochemical smog is formed from nitrogen oxides. Thus option D is correct.

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Answer:

Explanation: when electric current is passed through water, water dissociates into hydrogen and oxygen. Hydrogen is deposited over negative pole and oxygen is deposited over positive pole. Deposition of hydrogen and oxygen at different poles is visible in the form of bubbles.

Answer:

Explanation:

Here, we want to get which of the compounds have the highest percentage by mass of nitrogen

What we have to do here is to divide the mass of nitrogen atoms in the compound by the molecular mass of the compound

a) NH3

The atomic mass of nitrogen is 14 amu, the atomic mass of hydrogen is 1 amu

The molar mass is thus 14 + 3(1) = 17 g/mol

The percentage by mass of nitrogen will be

14/17 * 100 = 82.35 %

b) HCN

The atomic mass of carbon is 12 amu

Thus, we have the molar mass as

1 + 12 + 14 = 27 g/mol

Percentage of nitrogen by mass will be : 14/27 * 100 = 51.85 %

c) For N2O

The atomic mass of oxygen is 16 amu

The molar mass of the compound will be 14(2) + 16 = 44 g/mol

Percentage of nitrogen by mass will be = 28/44 * 100 = 63.64 %

d) NI3

The atomic mass of iodine is 127 g/mol

So the molar mass of the compound will be:

14 + 3(127) = 395 g/mol

Percentage by mass of nutrogen will be

14/395 * 100 = 3.54 %

From what we have, the highest percentage by mass of nitrogen is 82.35 % and that belongs to ammonia (NH3)

Answer:

Explanation:

To find the number of entities in a given substance we use the formula

N = n × L

where n is the number of moles

N is the number of entities

L is the Avogadro's constant which is

6.02 × 10²³ entities

From the question

n = 2.5 moles

We have

N = 2.5 × 6.02 × 10²³ = 1.505 × 10²⁴

We have the final answer as

Hope this helps you

Answer:

17

Explanation:

br is liquid

cl is gas

and iodide is solid

zn + 2 AgCI-> ZnCI2+ 2Ag

2 FeCI3+ 3 H2s->___FeCI2+ 6 HCI+___s

2 Ag2O-> 4 Ag+ O2

4AI2O3-> 3 AI+ 2O2

2 K+ 2H2O-> 2 KOH+ H2

Caco3-> CaO+ CO2

2 MG+ O2-> 2MgO

CO+ 3 Fe2O3-> 2 Fe+ 3CO2

2 H2+ 3 Fe2O3-> Fe+ 3H2O

HCI+ 2 ZN-> H2+ ZnCI2

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The molarity of the silver nitrate solution in the 200.00 mL flask is 0.22856 M.

To calculate the molarity of the solution in the 200.00 mL flask, we must need the number of moles present and the volume (200.00 mL = 0.20000 L).

To obtain the number of moles present, we can calculate the mass of AgNO₃ in the 200.00 mL sample and then use the molar mass of silver nitrate (M = 169.87 g/mol) to calculate the number of moles.

So, if there's 97.364 g of silver nitrate in the 1000.00 mL flask, we can use a simple proportion to calculate the mass present in 79.763 mL:

97.364 g : 1000.00 mL = X : 79.763 mL

X = 97.364 g * 79.763 mL / 1000.00 mL = 7.7660 g

This same mass is present in the final 200.00 mL solution, as it is merely diluted. So, we can now calculate the number of moles (n) of silver nitrate:

n = m/M

n = 7.7660 g / 169.86 g/mol

n = 0.045712 mol

Finally, we can use this to calculate the molarity (c) of the final solution:

c = n/V

c = 0.045712 mol / 0.20000 L = 0.22856 M

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Answer:

Gold

Explanation:

To recognize what element this is, we can simply look at the last orbital (5d9) and go to the periodic table and see what element is in that final orbital.

We go to row 6 (because of the 6s orbital at the beginning of this row) and then we see that our 6s orbital is full with 2 electrons, then our 4f orbital is full with 14 electrons, and our 5d orbital is not full where we only have 9 electrons instead of 10.

We then go to our 5d orbital and count 9 times into that orbital and end up with our final element being Gold (Au).

Answer:

Cyclone Movement

Explanation:

To form a cyclone, warm, moist air over the ocean rises upward from near the surface. As this air moves up and away from the ocean surface, it leaves is less air near the surface.

So basically as the warm air rises, it causes an area of lower air pressure below.

The enzyme that catalyzes the synthesis of ATP as hydrogen ions flow down their concentration gradient is called ATP synthase.

In the inner mitochondriаl membrаne, hydrogen ions hаve just one chаnnel аvаilаble: а membrаne-spаnning protein known аs АTP synthаse. Conceptuаlly, АTP synthаse is а lot like а turbine in а hydroelectric power plаnt. Insteаd of being turned by wаter, it’s turned by the flow of hydrogen ions moving down their electrochemicаl grаdient. Аs АTP synthаse turns, it cаtаlyzes the аddition of а phosphаte to АDP, cаpturing energy from the proton grаdient аs АTP.

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The predominant chemical species affecting the pH is H₃O⁺, but the pH value of the resulting solution is actually 1.26.

To calculate the pH value of the resulting solution we need the number of moles of H⁺ ions (n) and the volume of the solution (V). The volume is easy - it is the sum of the volumes of the barium hydroxide solution (13.90 mL = 0.01390 L) and the hydrochloric acid solution (45.00 mL = 0.04500 L)

V(total) = V(Ba(OH)₂) + V(HCl)

V(total) = 0.01390 L + 0.04500 L = 0.05890 L

Now we need to calculate the number of moles of H⁺ (H₃O⁺) ions. The number of moles of H⁺ ions in the HCl solution is:

n(H⁺) = c(HCl) * V(HCl)

n(H⁺) = 0.300 M * 0.04500 L = 0.0135 mol

On the other hand, the number of moles of OH⁻ ions is double the number of moles of barium hydroxide, because 1 mol of barium hydroxide releases 2 moles of OH⁻ ions:

n(OH⁻) = 2 * c(Ba(OH)₂) * V(Ba(OH)₂)

n(OH⁻) = 2 * 0.370 M * 0.01390 L = 0.010286 mol

The number of moles of H⁺ ions is greater than the number of moles of OH⁻ ions, so after the neutralization, we will have an excess of H⁺ ions:

n(H₃O⁺) = n(H⁺) - n(OH⁻)

n(H₃O⁺) = 0.0135 mol - 0.010286 mol = 0.003214 mol

We can now finally calculate the concentration of H₃O⁺ ions in the final solution:

c(H₃O⁺) = n(H₃O⁺) / V(total)

c(H₃O⁺) = 0.003214 mol / 0.05890 L = 0.05457 M

From this, we can find the pH value of the solution:

pH = -log(c(H₃O⁺))

pH = -log(0.05457)

pH = 1.26

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Answer:

I think it's carry energy, but I'm not sure

Answer:

The average atomic mass for an element is calculated by summing the masses of the element's isotopes, each multiplied by its natural abundance on Earth. Since beryllium has only one naturally occurring isotope. The average atomic mass of beryllium is the mass of Be-9 isotope multiplied by 100%.

Explanation:

Answer:3.381 X 10^(-11)

Explanation:

The formula for buoyant force is F = -Volume*density*gravitational acceleration. Convert volume and density to SI units and then apply them in the formula where gravitational acceleration is 9.8m/s^2. Done

Answer:

67 electrons

Explanation:

Most of the time, the number of protons is the same as the number of electrons because of their relation.

Consider the hydrate calcium chloride dihydrate hydrogen atoms are in the compound are four

Hydrate calcium chloride dihydrate is the excellent water soluble crystalline calcium sources used compatible with chloride and chloride compounds can conduct electricity when fused or dissolved in water and here given compound is CaCl₂ × 2H₂O

So in that compound the hydrogen atom are four because this compound or this equation is balanced so in that compound four hydrogen atom are present

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Answer:

4

Explanation:

phenol does not react with NaHCO3 , phenol solubility in water is very less about 8g in 100mL of water , so it will be present in organic layer (methylene chloride) , methylene chloride has a density of 1.33g/mL greater than water so it will be below layer in which phenol is present.

Immiscible liquids are separated using a separatory funnel, or sep funnel. Two layers appear in a separatory funnel when two immiscible liquids are added. The lower layer will be made up of the denser solvent. Most halogenated solvents are less dense than water, but most non-halogenated solvents are.

A separating funnel is used by adding the two phases and the mixture to be separated via the top while keeping the stopcock at the bottom closed. After then, the funnel is shut and gently shaken by being inverted several times. If the two solutions are combined too vigorously, emulsions will form.

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