Helen goes to the doctor and has a thyroid test done. She receives 20 grams of radioactive iodine. After 8 hours, 10 grams of the iodine have broken down. After 16 hours, there are 5 grams of iodine left.
What is the half-life of the radioactive iodine?
8 hours

Answer:

3Ca(OH)2 = 3(40+2(16+1))

= 222

448.2 ÷ 222 = 2.02mol

6NaOH = 6(23+16+1)

= 240

240 × 2.02mol = 484.5 g

AlCl 3 is Lewis base,PH3 is Lewis base,BH3 is Lewis acid ,BF3 is Lewis acid.

The crucial step is AlCl 3 accepting a chloride ion lone-pair to generate AlCl 4 and the highly acidic, or electrophilic, carbonium ion. Lewis bases:  RCl +AlCl 3 → R + + AlCl 4−, etc. [ edit] The highest occupied molecular orbital (HOMO) of an atomic or molecular species that is strongly localised is known as a Lewis base.Lewis acid borane (BH3) has three hydrogen atoms and one boron atom in its molecule. The Lewis structure of borane features a single connection connecting each hydrogen atom to boron (BH3). Only three bonds surround the boron atom, and there are no lone pairs on the atom itself. We will learn how to draw the BH3 Lewis structure in this lesson.Only six electrons orbit the boron atom, according the Lewis structure of BF3. As a result, the boron atom's octal is incomplete. Borane BF3 is therefore regarded as a Lewis acid.A highly poisonous gaseous chemical is phosphorus. Three sigma bonds and one lone pair are present around the phosphorus atom in the Lewis structure of phosphine (PH3). Hydrogen and phosphorous atoms have no charges. The trigonal pyramidal shape of PH3 is a fundamental shape.

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Choloracetic acid, 12 g. The colorless solution of the white crystalline substance known as chloroacetic acid.

Up to 80% of the solution can be acidic. By inhalation, ingestion, and skin contact, it is poisonous. It corrodes flesh and metals.

The equilibrium of the buffer is

CH2ClCO2 + H+ HCH2ClCO2

PKA = Log Ka

Ka: [CH2ClCO2] = 1,3 x 103. "H+" / "HCH2ClCO2"

Using the Henderson-Hasselbalch formula:

pH equals pka plus log10 [A]/[HA].

2,89 + log10 [A] / [HA] = 3,01

1,318 = [A⁻] / [HA]

Since chloroacetic acid (HA) has a molar concentration of 0,20M

[A⁻] = 0,26 mol/L

There are 500 mL plus 0.5 L.

Chloroacetic acid is equal to 0,26 mol/L x 0,5 l, or 0,13 moles. By weight:

Choloracetic acid is equal to 0,13 mol (94,5g / 1mol) = 12 g.

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The diagrams of zonation in lakes and oceans with correct targets are :

a) fresh plant may be rooted here

b) littoral zone

c) limnetic zone

d) alternately dry and submerged

e) extends to edge of the continental shelf

f) generally low nutrient levels

g) light penetrates here

h) no photosynthesis occurs here

i) benthic zone

There are zones which divided the lakes. they are separated by the water from the top to bottom and the side to the side. that is named as : the littoral zone , the limnetic zone, the profundal zone , the benthic zone and the euphotic zone . the waters temperature will be affected the density. there are several zones in the ponds and the lakes. these are dived by the water column.

The limnology divides the lakes in the three types of zones ., that is the limnetic zone, the littoral zone and the benthic zone.

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The statement that is  true about the elements;

Atom X and Atom Y are in the same row on the periodic table. Option C

We know that the periodic table has to do with an arrangement of the elements in an order that is systematic. As such, when we look at the periodic table, we are looking at a systematization of the elements in a way that it is quite easy for us to be able to identify the elements.

Now we know that the mass number is the sum of the atomic number which in turn is the proton number and the number of the neutrons in the atom.

We know that the atomic number is what would tell us the group to which the element has been found to belong and in this case we can see that element X is just right to element Y in the periodic table.

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Rank the relative viscosity and vapor pressure of the substances Paraffin, hexadecane, octane, 2,2,4-trimethylpentane,methane.

In addition to being a fuel or fuel component for diesel and tractor engines, paraffin is frequently utilized as a fuel for jet engines and rockets. These are some typical applications for paraffin: Paraffin wax, a white or colorless soft solid that is used as a lubricant, in candles, crayons, electrical insulation, and petroleum jelly, is a complex mixture of hydrocarbons that is especially obtained from distillates of wood, coal, petroleum, or shale oil. It is primarily used in coating and sealing, candles, rubber compounding, pharmaceuticals, and cosmetics. Consuming excessive amounts of paraffin might result in intestinal blockage, which can bring on symptoms including nausea, vomiting, and constipation. An individual with a dye allergy could get tongue swelling if the paraffin contains that dye.

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The chemical species in solution S2 Fe(s)+NiCl2(aq) → FeCl2(aq)+Ni(s)

Fe(s) ------> [tex]Fe^{2+}[/tex] + 2e                              (Oxidation)

[tex]Ni^{2+}[/tex] (aq) + 2e ------> Ni(s)                        (Reduction)

Galvanic Cell

Galvanic cells employ the electrical energy generated by the transport of electrons during a redox reaction to carry out practical electrical work. By separating the oxidation and reduction half-reactions and connecting them with a wire so that the electrons must pass through the wire, it is possible to gather the electron flow.

Write a balanced equation for the half-reaction that happens at the cathode of this cell = Ni (aq) + 2e ------> Ni(s)

Write a balanced equation for the half-reaction that happens at the anode of this cell = Fe(s) ------> [tex]Fe^{2+}[/tex] + 2e.

Of what substance is E1 made? = Fe

of what substance is E2 made? = Ni

What are the chemical species in solution S1? = [tex]Fe^{2+}[/tex]

What are the chemical species in solution S2? = [tex]Ni^{2+}[/tex]

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the overall balanced cell reaction for the following voltaic cell

Hg2Cl2(s) + Cu(s) ® 2Hg(l) + Cu2+(aq) + 2Cl-(aq)

The cell reaction, also known as the total reaction, is the reaction that occurs within the cell as a whole and is expressed under the assumption that the right electrode is the cathode and that the spontaneous reaction is the one in which reduction takes place in the right-hand compartment.Galvanic, also known as Voltaic, and electrolytic cells are the two varieties of electrochemical cells. While electrolytic cells utilize non-spontaneous reactions and therefore need an external electron source, such as a DC battery or an AC power source, galvanic cells get their energy from spontaneous redox reactions.

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An organism with the genotype of AaXx can produce gametes containing  either AX, Ax, aX, ax  if the two genes are unlinked .

An organism's genotype is the complete set of its genetic material. [1] Genotype can also be used to refer to the alleles or variants that an individual has at a particular gene or locus. The number of alleles an individual can have for a particular gene depends on the number of copies of each chromosome (also called polyploidy) found in that species. Diploid species like humans have two complete sets of chromosomes. This means that each individual has her two alleles for a particular gene. If both alleles are the same, the genotype is said to be homozygous. If the alleles are different, the genotype is called heterozygous.

Genotypes contribute to the phenotype, observable traits and characteristics of an individual or organism. The extent to which genotype influences phenotype depends on the trait.

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A well-known NMR technique called diffusion ordered spectroscopy (DOSY) provides diffusion coefficients for specific resonances in NMR spectra.

The main applications of DOSY are the analysis of small molecule mixtures and the oligomeric state of biomolecules. The spreading Self-Diffusion (SD)-NMR and diffusion ordered spectroscopy are two common names for the NMR technology (DOSY). This is accomplished by fusing magnetic field gradients, which encode spatial information, with radio-frequency pulses, which are commonly employed in NMR spectroscopy. Magnetic field gradients are used by Diffusion Ordered Spectroscopy (DOSY) to examine diffusion processes in both solid and liquid materials. Liquid structure is discovered using NMR spectroscopy. It is also used to figure out how soluble chemical molecules are structured.

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The Solubility Of Fe(OH)₂ In Water At 25 °C Is Measured To Be 5.2x 10⁻⁴ Fe(OH)₂ Ksp value is 5.6 × 10⁻¹⁰.

The chemical reaction is given as follows :

Fe(OH)₂ ⇄  Fe²⁺    +   2OH⁻

Ksp expression for the given reaction is given as follows :

Ksp = [Fe²⁺] [OH⁻]²

the solubilty S =  5.2x 10⁻⁴

so , the Ksp = S × (2S)²

                    = 4S³

Ksp = 4 ×S³

      = 4 × (  5.2x 10⁻⁴ )³

      = 4 × 140.6 × 10⁻¹²

      = 5.6 × 10⁻¹⁰

The solubility product value for Fe(OH)₂   that is Ksp value is 5.6 × 10⁻¹⁰.

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Atomic structure: odd number of F atoms; periodicity: the number of F atoms rises as the atomic number of the central halogen atom rises; ClF, ClF3.

A complicated configuration of negatively charged electrons organized in predetermined shells surrounding a positively charged nucleus is an atom. The majority of the atom's mass is located in this nucleus, which is made up of protons and neutrons (except for common hydrogen which has only one proton). The size of each atom is similar. The angstrom (), which is equal to one tenth of a meter, is a practical measure of length for calculating atomic sizes. A typical atom measures 2-3 in diameter.

Atomic structure physics as we know it now began with J. J. Thomson's discovery of the electron in 1897. Within the outlined energy shells surrounding the nucleus, the negatively charged electrons move in a random way. The amount and arrangement of an atom's electrons determine most of its properties.

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As per law of conservation of energy, energy  can be converted from one form to another, renewable sources of energy best meets needs of society as they are everlasting and can be renewed from fossil fuels.

According to law of conservation of energy, it is evident that energy is neither created nor destroyed rather it is restored at the end of a chemical reaction .

Renewable sources of energy are extensively being used as they long lasting and provide less carbon footprints.Every source of energy obeys law of conservation of energy by it getting transformed into another.

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Answer:

2.02 L

Explanation:

The volume of a gas is directly proportional to its temperature, according to the ideal gas law. This means that as the temperature of a gas decreases, its volume will also decrease.

To determine the new volume of the balloon as the temperature drops from 311 K to 295 K, we can use the ideal gas law to calculate the new volume of the gas:

PV = nRT

Where:

P = the pressure of the gas (assuming it remains constant)

V = the new volume of the gas

n = the number of moles of the gas (assuming it remains constant)

R = the universal gas constant

T = the new temperature of the gas

Since we know the pressure, number of moles, and universal gas constant, we can solve for the new volume of the gas by substituting in the known values and solving for V:

V = nRT / P

Substituting in the values from the problem, we get:

V = (n * R * 295 K) / P

Since the number of moles and the universal gas constant are constants, we can simplify the equation to:

V = k / P

Where k is a constant equal to the product of the number of moles, the universal gas constant, and the original temperature of the gas (in this case, k = n * R * 311 K).

Since we know the value of k and the pressure of the gas, we can solve for the new volume of the gas by substituting in the known values:

V = (k / P)

= (n * R * 311 K) / P

= (2.07 L * 8.31 L * atm / mol * K * 311 K) / P

= 2.02 L

Therefore, the new volume of the balloon is approximately 2.02 L.

Specific heat capacity of a substance is the amount of heat required to raise the temperature by one degree Celsius of one gram of a substance. Therefore, the total enthalpy of the given reaction is -781.44KJ.

Enthalpy term is basically used in thermodynamics to show the overall energy that a matter have. Mathematically, Enthalpy is directly proportional to specific heat capacity of a substances.

Mathematically,

q = n ×ΔH

where

q = amount of heat

n = no of moles

ΔH = enthalpy

n = w / M.M

w = given mass

M.M = molar mass

4CH[tex]_3[/tex]NH[tex]_2[/tex]+2H[tex]_2[/tex]O[tex]\rightarrow[/tex]3CH[tex]_4[/tex]+CO[tex]_2[/tex]+4NH[tex]_3[/tex]   ΔH=-138.8KJ

number of moles of methyl amine=175/31.06

                                                       =5.63moles

enthalpy for reaction of one mole of methyl amine=-138.8KJ

enthalpy for reaction of 5.63 mole of methyl amine=-138.8KJ×5.63

                                                                                     =-781.44KJ

Therefore, the total enthalpy of the given reaction is -781.44KJ.

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Combustion of 31.68 g of a compound containing only carbon, hydrogen, and oxygen produces 36.67 g CO₂ and 15.01 g H₂O. the empirical formula of the compound is CH₂O.

given that :

mass of CO₂ = 36.67 g

mass of H₂O = 15.01 g

total mass of compound = 31.68 g

moles of CO₂ = 36.67 / 44

                       = 0.833 mol

moles of C = 0.833 mol

moles of  H₂O = 15.01 / 18

                        = 0.833 mol

moles of H = 2(0.833)

                  = 1.667 mol

mass of carbon = 0.833 × 12

                           = 10 g

mass of hydrogen = 1.667 × 1

                               = 1.667 g

mass of oxygen = 31.68 - ( 10 + 1.67 )

                             = 20 g

moles of Oxygen = 20 / 16

                             = 1.25 mol

dividing by the smallest one :

C = 0.833 / 0.833 = 1

H = 2

O = 1

The empirical formula is CH₂O.

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Answer:

2 g of the parent isotope is left.

Explanation:

The half-life of a radioactive isotope is the amount of time it takes for half of the isotope to decay. In this case, the half-life of the isotope is 8 days, which means that after 8 days, half of the isotope will have decayed.

To determine how much of the parent isotope is left after 40 days, we need to calculate how many half-lives have passed in that time. Since the half-life is 8 days, and 40 days have passed, we can divide 40 by 8 to find the number of half-lives that have occurred: 40 / 8 = 5

Since 5 half-lives have passed, we can calculate the amount of the parent isotope that is left by multiplying the original amount of the isotope by 1/2 to the power of the number of half-lives that have passed: 64 * (1/2)^5 = 64 * (1/32) = 2 g

Therefore, after 40 days, only 2 g of the parent isotope is left.

Alkynes are hydrocarbons containing a carbon-carbon triple bond. Their general formula is CnH2n-2 for molecules with triple bonds.

Alkynes undergo many of the same reactions as alkenes but can react twice due to the presence of two p-bonds on the triple bond. Ethyne is commonly known by the trivial name acetylene. It is the simplest alkyne, consisting of two carbon atoms joined by a triple bond, where each carbon can bond to a hydrogen atom.

Molecules containing a triple bond between two carbon atoms are called alkynes. A triple bond consists of one σ bond and two π bonds. As for the hydrogen atoms, this compound is unsaturated, so the extra electrons are exchanged with two carbon atoms forming a double bond.

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An endothermic process from the list would be the melting of ice cubes. Option A.

Endothermic processes are processes that absorb energy from the surrounding. Chemically, endothermic reactions are reactions in which the products are at higher energy level than the reactants.

Endothermic processes are different from exothermic processes. Exothermic processes are processes that gives off energy to the surrounding instead of taking from it.

In order for ice cubes to melt, they need to absorb energy from external sources. In order words, the melting of ice cubes is analogous to an endothermic process.

Burning of sugar and candle give off heat energy to the surrounding. When water vapor condenses, they also give off energy in order to change state from gas (vapor) to liquid. In other words, the burning of sugar and candle, as well as the condensation of rain from water vapor are all exothermic processes.

The only process that is endothermic is the melting of ice cubes.

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Answer:Co2O3

Explanation:

look it up

Answer:

Co2O3

Explanation:

when you write any formula you apply the criss-cross method where you write the charges of each substance

Co3 and O2

applying the criss-cross method( you switch the charges number, in this case you switch the 2 and the 3) :-

Co2 and O3

so Co2O3

The volume occupied at 25 °C. Remember to convert between °C and K. V2 = 3.311 L is the correct answer.

What is volume?

Volume is the measure of the amount of space occupied by an object or a substance. It is measured in three dimensions: length, width, and height. In the International System of Units (SI), it is measured in cubic meters (m3). Volume is also commonly measured in liters (L), gallons (gal), or cubic feet (ft3). Volume can also refer to the amount of a substance or object, such as the volume of a gas or the volume of a liquid.

Temperature and Volume equation

Given,

The volume at -12°C = 2.90L

Temperature, T1 = -12°C

= (-12°C + 273)

= 261K

And, Volume at 25°C = ?

(25°C + 273)K

= 298K

Now, by using this equation:-

V1/T1 = V2/T2

V2 = V1 x T2/T1

V2 = 2.90L x 298K/261K

V2 = 3.311L

Hence, The volume at  25°C will be 3.311L

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Because NH3 molecules in the liquid phase require energy to overcome their intermolecular interactions and transform into free gas molecules, this expression reads NH3(l)— NH3(g). Heat is transferred from the environment to the system during phase shifts.

Ammonia has the chemical formula NH3 and is a colourless gas.Nitrogen and hydrogen make up its composition. Its name in aqueous form is ammonium hydroxide. This inorganic substance smells strongly. It is hazardous and corrosive in its concentrated form. Ammonia has a density of 0.769 kg/m3 at STP, making it lighter than air. It is frequently employed as fertiliser. Additionally, it is employed in the production of explosives like TNT and nitrocelluloseAdditionally, it is employed in the manufacture of soda ash and the Ostwald process to produce nitric acid. A strong alkali, such as sodium hydroxide or calcium hydroxide  2NH4Cl + Ca(OH)2 → CaCl2 + 2H2O + 2NH3(g) is heated with an ammonium salt, such as ammonium chloride NH4Cl, to produce ammonia (g)

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if a mole of argon gas is warmed to 700 k as well as its pressure is reduced to 0.0800 bar, then measure the change in entropy. Suppose that the ideal gas behaviour is 38.61 J/K.

Entropy, broad sense, serves as a metric for energy quality, with lower entropy indicating better quality. Entropy is lower for energy that's been carefully arranged (the efficient library). The random-pile library is a chaotic energy storage device with high entropy. All parts of our daily life are impacted by entropy, which would be merely a measure of disorder. In actuality, it may be considered humanity's greatest tax. Dysfunction spreads over time if left unchecked. Systems collapse into chaos when energy diffuses. Something is much more chaotic the more

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The volume of the object is 1.5ml.

This refers to the space occupied within the boundaries of an object in three-dimensional space. It is also called the capacity of the object.

In the question:

ρ = 400 g/mL

m = 600 mg

v = ?

Formular for calculating density ρ:

ρ = m/v

Where,

ρ= Density of the object

m= Mass of the object

v = volume of the object

Were are given the values of density and mass in the question. We are to calculate the volume.

Makinig v subject of the formular we have:

v = m/ρ

v =  600 mg

      400 g/mL

v = 1.5ml

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This chemical reaction: ca(s) zncl2(aq)zn(s)cacl2(aq) then, balanced half-reactions describing the oxidation and reduction that happen in this reaction is Ca (s) + ZnCl2 (aq) ---> Zn (s) + CaCl2 (aq).

When the substrate's oxidation states change, a chemical reaction known as redox (reduction-oxidation) takes place. Reduction occurs when electrons are obtained or the oxidation state drops; oxidation occurs when electrons are lost or the oxidation state increases. There are two types of redox reactions: During an electron transfer, only one electron (usually) travels from the reducing agent to the oxidant. This type of redox reaction is frequently discussed in terms of redox couples and electrode potentials. When one substrate gives way to another, an atom transfers. When iron rusts, for example, oxygen's oxidation state decreases as it receives electrons released by the iron, while the oxidation state of the iron atoms increases as the iron transforms into an oxide. Despite the fact that oxidation processes are typically related to the generation of oxides, other chemical species can carry out the same function.  To weaken C=C (and other) bonds, hydrogen atoms are exchanged during hydrogenation.

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Ozone decomposes to oxygen according to the equation 2O₃(g)⟶3O₂(g). Create the equation that ties the rate expressions for this reaction to the creation of oxygen and the disappearance of O₃.

Given that there are more reactants in a given volume of space, increasing the concentration of reactants improves the likelihood that they will collide in the proper direction. As a result, the reactions rate would increase if the reactants were concentrated more. more often with each other. As a result, the reaction progresses more quickly as the temperature rises. Since the molecules will have less kinetic energy, travel more slowly, and collide less frequently as a result of a lower temperature, the rate of reaction will also be reduced.

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The statements that are true about the organization of the periodic table are as follows:

Periodic table is a tabular chart of the chemical elements according to their atomic numbers so that elements with similar properties are in the same group (column).

The periodic table of chemical elements, often called the periodic table, organizes all discovered chemical elements in rows (called periods) and columns (called groups) according to increasing atomic number.

This suggests that options B and D are correct regarding the arrangement of elements in the periodic table.

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1 A + two C and d → C + S t where rate=k[A][B][rate] 2. An experiment with [A]o = 0.000847 T s as well as [B]o = 1.11 M was run for a predefined number of seconds. The slope of a ln[A] vs. grown steadily was -9.43. rate of reaction is 3.62m/s

Slope and slant both refer to an incline up from a reference surface or line that is generally straight. The ground slopes (either upward or straight down) sharply here. To slope is to slope vertically in an ambiguous path A line's steepness could be determined by looking at its slope. Altitude is calculated mathematically as "rise over run."

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Only two electrons can be filled in an orbital with a magnetic quantum number (ml) +2.

The set of numbers that defines the position and energy of the electron filled in a specific orbital are called quantum numbers. Four quantum numbers are principal, azimuthal quantum number, magnetic, and spin quantum numbers.

The principal quantum number (n) denotes the principal electron shell of the atom and the most probable distance between the nucleus and the electrons. The azimuthal quantum number (l) denotes the shape of an orbital in which an electron is present.

The magnetic quantum number denotes the total number of orbitals in a subshell and the orientation of these orbitals.  The value of the spin quantum number (s) denotes the direction in which the electron is spinning.

For the value of n = 2, we have five values of ml which are +2, +1, 0, -1, and -2. Every value of ml represents one d-orbital. Each orbital can have two electrons.

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