the eye is a substance of which major body system

Answer:

oxygen, silicon, iron, calcium, sodium

Explanation:

these are all found in space rocks known as meteorites. hope this helps :)

Answer:

See explanation and image attached

Explanation:

The addition of hypohalous acids to alkenes follows the Markovnikov rule. This rule states that the negative part of the addendum is joined to the carbon atom with the least number of hydrogen atoms (more substituted carbon atom).

In the addition of hypohalous acids, the halogen is the positive end of the addendum and the OH^- is the negative end of the addendum. This explains the product shown in the image attached.

Answer:

The number of moles of formic acid needed is 4.5x10⁻³ moles.

Explanation:

We can find the moles of formic acid using the Henderson-Hasselbalch equation:

[tex] pH = pKa + log(\frac{[CHOO^{-}]}{[CHOOH]}) [/tex]

We know:

pH = 3.60

pKa = 3.75                    

By solving the above equation for [CHOO⁻]/[CHOOH] we have:

[tex] \frac{[CHOO^{-}]}{[CHOOH]} = 10^{(pH - pKa)} = 10^{(3.60 - 3.75)} = 0.71 [/tex]

[tex] [CHOO^{-}] = 0.71[CHOOH] [/tex]  (1)

Now, we have:

[tex] [CHOOH] + [CHOO^{-}] = 0.03 M [/tex]   (2)

By entering equation (1) into (2) we have:

[tex] [CHOOH] + 0.71[CHOOH] = 0.03 M [/tex]

[tex] [CHOOH] = 0.018 M [/tex]

Hence, the concentration of formate is:

[tex] [CHOO^{-}] = (0.03 - 0.018)M = 0.012 M [/tex]

Finally, the number of moles of formic acid is:

[tex] n_{CHOOH} = [CHOOH]*V = 0.018 \frac{mol}{L}*0.250 L = 4.5 \cdot 10^{-3} moles [/tex]

Therefore, 4.5x10⁻³ moles of formic acid are needed.

I hope it helps you!  

We have that for the Question "How many moles of formic acid will you need?"

It can be said that

From the question we are told

to prepare 250.0 mL of a pH=3.60, total buffer concentration of formic acid + formate of 0.030 M, The pKa of formic acid is 3.75.

Let [tex]1+COO4 = X, 1+COON = (0.03-X)[/tex]

[tex]pH = pKa + log\frac{1+COON}{1+COO4}\\\\3.6 = 3.75 +log\frac{0.03-X}{X}\\\\log\frac{0.03-X}{X} = 3.6 - 3.75\\\\\frac{0.03-X}{X} = 0.708\\\\X = 0.0175M[/tex]

Therefore,

[tex]moles of formic acid = 0.0175*0.25mole\\\\= 4.39*10^{-3}mole[/tex]

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Answer:

That's not possible. When a limiting reactant is called out in a stoichiometry problem, what that means is there's enough of all the other reactants for the limiting one to be completely consumed in the formation of product/products

Explanation:

monomer

smaller molecules that are used to prepare a polymer.

may or may not be equivalent to the repeat unit.

oligomer

a molecule consisting of several repeat units of a monomer, but not large enough to be considered a polymer

polymers

arge, usually chainlike molecules that are built from small molecules called monomers. Polymers form the basis for synthetic fibers, rubbers, and plastics and have played a leading role in the revolution that has been brought about in daily life by chemistry.

first synthetic polymers were produced as

by-products of various organic reactions and were regarded as unwanted contaminants.

first completely synthetic plastic

Bakelite, a substance that when molded to a certain shape under high pressure and temperature cannot be softened again or dissolved. Bakelite is a thermoset polymer. In contrast, cellulose nitrate is a thermoplastic polymer; that is, it can be remelted after it has been molded.

ethylene

basic raw material in the production of polyethylene and other important compounds. Over 135 million tons of ethylene were produced worldwide in 2010 for use in the polymer, petrochemical, and plastic industries. Ethylene is produced industrially in a process called cracking, in which the long hydrocarbon chains in a petroleum mixture are broken into smaller molecules.

monomer ethylene (C2H4) is

a gas at room temperature, but when polymerized, using a transition metal catalyst, it is transformed into a solid material made up of long chains of -CH2- units called polyethylene. Polyethylene is a commodity plastic used primarily for packaging (bags and films).

nylon

the silky appearance and strength of this thread and realized that nylon could be drawn into useful fibers.

The reason for this behavior of nylon is now understood. When nylon is first formed, the individual polymer chains are oriented randomly, like cooked spaghetti, and the sub- stance is highly amorphous. However, when drawn out into a thread, the chains tend to line up (the nylon becomes more crystalline), which leads to increased hydrogen bonding between adjacent chains. This increase in crystallinity, along with the resulting increase in hydrogen-bonding interactions, leads to strong fibers and thus to a highly useful mate- rial. Commercially, nylon is produced by forcing the raw material through a spinneret, a plate containing small holes, which forces the polymer chains to line up.

polyethylene

simplest and one of the best-known polymers, constructed from ethylene monomers.

CH2=CH2

Polyethylene is a member of one subset of synthetic polymers classified as plastics.

properties of polyethylene

Polyethylene is a tough, flexible plastic used for piping, bottles, electrical insulation, packaging films, garbage bags, and many other purposes.

Its properties can be varied by using substituted ethylene monomers. For example, when tetrafluoroethylene is the monomer, the polymer Teflon.

Answer:

See explanation

Explanation:

Substances are composed of bands. A band is a group of molecular orbitals, the energy differences between them are so small that the system behaves as if a continuous, non-quantization of energy within the barrier is possible.

Materials consists of a valence band and a conduction band separated by a band gap. A band gap occurs when the energy difference between two bands is significant.

The magnitude of band gap determines whether a material will be a metal, nonmetal or metalloid.

Metals have a very little band gap hence they are able to conduct electricity more effectively than other materials, such as ionic and covalent substances.

Answer:

helium is the smallest and francium is the largest

Answer:

Such a relationship between atomic number and atomic radius is a direct correlation. an inverse correlation. According to Coulomb's Law, as the atomic number increases within a series of atoms, the nuclear attraction for electrons will also increase, thus pulling the electron(s) closer to the nucleus.

Explanation:

Answer:

The prefixes are fluoro-, chloro-, bromo-, and iodo-. Thus CH 3CH 2Cl has the common name ethyl chloride and the IUPAC name chloroethane. Alkyl halides with simple alkyl groups (one to four carbon atoms) are often called by common names.05‏/06‏/2019

The IUPAC name of this compound is 2,3- dichlorobutane.

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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Answer:

O constant specific heat

Explanation:

[tex]\bull\sf m=0.47kg[/tex]

[tex]\bull\sf \Delta T=T_f-T_i=48.4-30.5=17.9°C[/tex]

[tex]\bull\sf Q=1.65\times 10^4J[/tex]

We know according to thermodynamics

[tex]\\ \sf\longmapsto Q=mc\Delta T[/tex]

[tex]\\ \sf\longmapsto c=\dfrac{Q}{m\Delta T}[/tex]

[tex]\\ \sf\longmapsto c=\dfrac{1.65\times 10^4}{0.47\times 17.9}[/tex]

[tex]\\ \sf\longmapsto c=\dfrac{1.65\times 10^4}{8.413}[/tex]

[tex]\\ \sf\longmapsto c=0.1961\times 10^4J/kg°C[/tex]

[tex]\\ \sf\longmapsto c=1961J/kg°C[/tex]

There is a golden role of solubility, polar solute dissolve in polar solvent and non polar solute dissolve in non polar solvent. Therefore, the correct option is option B that is Salt and water.

Solutions are a homogeneous mixture of two or more substances. A solution is a homogeneous mixture of solvent and solute molecules. Solvent is a substance that is in large amount in solution. solute is the substance which is in small amount in a solution. There are two types of mixture that is homogeneous and heterogeneous. Solution is a homogeneous solution.

Salt and water because salt is transparent and will dissolve into the water among given solute, salt NaCl is a polar solute which will dissolve in polar solvent that is water.

Therefore, the correct option is option B that is Salt and water.

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Answer:

[tex]115.625^{\circ}\text{F}[/tex]

Explanation:

[tex]m_1[/tex] = First mass of water = 12 oz

[tex]m_2[/tex] = Second mass of water = 20 oz

[tex]\Delta T_1[/tex] = Temperature difference of the solution with respect to the first mass of water = [tex](T-75)^{\circ}\text{F}[/tex]

[tex]\Delta T_2[/tex] = Temperature difference of the solution with respect to the second mass of water = [tex](T-75)^{\circ}\text{F}[/tex]

c = Specific heat of water

As heat gain and loss in the system is equal we have

[tex]m_1c\Delta T_1=m_2c\Delta T_2\\\Rightarrow m_1\Delta T_1=m_2\Delta T_2\\\Rightarrow 12(T-75)=20(140-T)\\\Rightarrow 12T-900=2800-20T\\\Rightarrow 12T+20T=2800+900\\\Rightarrow 32T=3700\\\Rightarrow T=\dfrac{3700}{32}\\\Rightarrow T=115.625^{\circ}\text{F}[/tex]

The final temperature of the solution is [tex]115.625^{\circ}\text{F}[/tex].

Answer:

D. It is a Mixture

Explanation:

It tells us it is a combination of substances. We do not know the states of these substances or the state of the new substance. However, we do know that it was physically combined. Hence, this is a mixture. (FYI If it was combined chemically, it would be a compound)

Answer:

Positive

Explanation:

There are more protons than electrons making it positive

Answer:

 [Ne] 3s² 3d³

Explanation:

According to aufbau's principle of filling electronic orbitals, the sublevels with lower energies are filled up before those with higher energies.

One important to know about this principle is that sublevels do not fill in numerical order.

The order of filling is;

 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f e.tc

From the given choices the wrong one is;

   [Ne] 3s² 3d³

3p fills up before 3d;

Answer:

The average atomic mass is closer to Si- 28 because this isotope is present in more percentage in the sample.

Explanation:

Given data:

Atomic mass of silicon= ?

Percent abundance of Si-28 = 92.21%

Atomic mass of Si-28 = 27.98 amu

Percent abundance of Si-29 = 4.70%

Atomic mass of  Si-29 = 28.98 amu

Percent abundance of Si-30 = 3.09%

Atomic mass of  Si-30 = 29.97 amu

Solution:

Average atomic mass = (abundance of 1st isotope × its atomic mass) +(abundance of 2nd isotope × its atomic mass)+(abundance of 2nd isotope × its atomic mass)  / 100

Average atomic mass = (92.21×27.98)+(4.70×28.98)+(3.09×29.97) /100

Average atomic mass =  2580.04 +136.21+92.61 / 100

Average atomic mass = 2808.86 / 100

Average atomic mass  = 28.08amu.

The average atomic mass is closer to Si- 28 because this isotope is present in more percentage in the sample.

Answer:

The average atomic mass of silicon would be closer to Si-28 as it is the most abundant isotope.

Explanation:

From PLATO

Answer:

The correct answer is c. Distillation

Explanation:

The volatility of a substance refers to the tendency to vaporize. The more volatility, more readily the substance vaporizes and passes from liquid state to gas state.

From the options, the only operation that separes substances by their tendency to vaporize is distillation. In distillation, evaporation and condensation processes at different temperatures are used to separe miscible liquid substances.

Therefore, the correct option is c. Distillation

Answer:

C. Distillation

Explanation:

EDGE2021

Answer:

c. 131 kPa

Explanation:

Hello!

In this case, since the relationship between volume and pressure is inversely proportional, based on the Boyle's law:

[tex]P_1V_1=P_2V_2[/tex]

Considering that the standard pressure is 101.325 kPa, we can compute the final pressure as shown below:

[tex]P_2=\frac{P_1V_1}{V_2}=\frac{620mL*101.325kPa}{480mL}\\\\P_2=131kPa[/tex]

Therefore, the answer is c. 131 kPa .

Best regards!!

Answer:

Just ask google for help

Explanation:

I always do it and get it right

Answer:

6.022×10²² molecules

Explanation:

Given data:

Volume of nitrogen = 224 L

Pressure = standard = 1 atm

Temperature = standard = 273 K

Number of molecules = ?

Solution:

PV = nRT

1 atm × 224 L = n × 0.0821 atm.L/mol.K × 273 K

224 atm.L = n ×22.41 atm.L/mol

n = 224 atm.L/22.41 atm.L/mol

n = 10 mol

1 mole contain 6.022×10²³ molecules

10 mol×6.022×10²³ molecules/ 1 mol

60.22×10²³ molecules

6.022×10²² molecules

Answer:

thank you! ladies... love the answer is A) 6.022 x 10 ^22

Explanation:

love this one!

have a good one everyone

Answer:

a. 122.6 mL / pH = 4.03

b. 193.6 mL / pH = 5.73

Explanation:

In the equivalence point we know: mmoles acid = mmoles base- And the pH in a titration between a weak base and a strong base, is acid, at the equivalence point. For the volume, we can replace the equation with the data given.

a. 0.125M . volume of acid = 65.5 mL . 0.234M

Volume of acid = (65.5 . 0.234) / 0.125 = 122.6 mL

Total volume at the equivalence point = 188.1 mL

b. 0.125M . volume of acid = 21.8 mL . 1.11 M

Volume of acid = (21.8 .  1.11) / 0.125 = 193.6 mL

Let's calculate the pH. In the equilavence point we have a neutralization reaction.

a. NH₃ + HCl → NH₄Cl

All the mmoles of protons (65.5 mL . 0.234M) react to ammonia, to obtain ammonium.

New concentration is: 15.32 mmoles / 188.1 mL = 0.0814 M

This is the [NH₄⁺] to determine the pH in the acid base equilibrium.

NH₄⁺  +  H₂O  ⇄  NH₃  +  H₃O⁺      Ka

Expression for Ka = [NH₃]  . [H₃O⁺] / [NH₄⁺]

5.6×10⁻¹⁰ = x² / (15.32 - x)

(We can avoid the quadratic equation 'cause Ka is so small)

√(5.6×10⁻¹⁰ . 15.32) = x → [H₃O⁺] = 9.26×10⁻⁵

pH = - log [H₃O⁺] → 4.03

b. CH₃NH₂ + HCl → CH₃NH₃Cl

All the mmoles of protons (21.8 mL . 1.11M) react to methylamine, to obtain methylammonium.

New concentration is: 24.2 mmoles / 193.6 mL = 0.125 M

This is the [CH₃NH₃⁺] to determine the pH in the acid base equilibrium.

CH₃NH₃⁺  +  H₂O  ⇄  CH₃NH₂  +  H₃O⁺      Ka

Expression for Ka = [CH₃NH₂]  . [H₃O⁺] / [CH₃NH₃⁺]

2.7×10⁻¹¹ = x² / (0.125 - x)

(We can avoid the quadratic equation 'cause Ka is so small)

√(2.7×10⁻¹¹ . 0.125) = x → [H₃O⁺] = 1.84×10⁻⁶

pH = - log [H₃O⁺] → 5.73

The pH of the equivalence point of 0.125M HCl with NH₃ is 4.03 and with CH₃NH₂ is 5.73.

In the acid - base titration, at the equivalence point equal moles of acid as well as of base are present.

First we calculate the volume of HCl by using the below equation as:

M₁ = molarity of NH₃ = 0.234 M

V₁ = volume of NH₃ = 65.5 mL

M₂ = molarity of HCl = 0.125 M

V₂ = volume of HCl = ?

V₂ =  (65.5 . 0.234) / 0.125 = 122.6 mL

Total volume at the equivalence point = 188.1 mL

Chemical reacion will be written as:

NH₃ + HCl → NH₄Cl

All moles of protons react with moles of ammonia, so new moles (n) will be calculated as:

n = molarity × volume

n = 65.5 mL × 0.234M = 15.32 moles

Now, concentration in terms of molarity will be 15.32 mmoles / 188.1 mL = 0.0814 M

pH in the acid-base reaction due to [NH₄⁺], as:

NH₄⁺  +  H₂O  ⇄  NH₃  +  H₃O⁺

Value of Ka for this reaction is = 5.6×10⁻¹⁰

According to the ICE table, Ka equation will be written as-

5.6×10⁻¹⁰ = x² / (15.32 - x)

x = [H₃O⁺] = 9.26 × 10⁻⁵

pH = - log [H₃O⁺] = 4.03

0.125M . volume of acid = 21.8 mL . 1.11 M

Volume of acid = (21.8 .  1.11) / 0.125 = 193.6 mL

Total volume at the equivalence point = 215.4 mL

Chemical reacion will be written as:

CH₃NH₂ + HCl → CH₃NH₃Cl

All moles of protons react with moles of ammonia, so new moles (n) will be calculated as:

n = 21.8 mL . 1.11M = 24.2 moles

Now, concentration in terms of molarity will be 24.2 moles / 215.4 mL = 0.11M

pH in the acid-base reaction due to [CH₃NH₃⁺], as:

CH₃NH₃⁺  +  H₂O  ⇄  CH₃NH₂  +  H₃O⁺

Value of Ka = 2.7×10⁻¹¹

According to the ICE table, Ka equation will be written as-

2.7×10⁻¹¹ = x² / (0.11 - x)

x = [H₃O⁺] = 5.4×10⁻⁶

pH = - log [H₃O⁺] = 5.73

Hence the value of pH will be 4.03 and 5.73 respectively.

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Answer:

–156 °C

Explanation:

The following data were obtained from the question:

Initial temperature (T1) = –20 °C

Initial volume (V1) = 140 mL

Final volume (V2) = 65 mL

Final temperature (T2) =?

Pressure = constant.

Next, we shall convert –20 °C to Kelvin temperature. This can be obtained as follow:

T(K) = T(°C) + 273

Initial temperature (T1) = –20 °C

Initial temperature (T1) = –20 °C + 273 = 253 K.

Next, we shall determine the new temperature of the gas as follow:

Initial temperature (T1) = 253 K

Initial volume (V1) = 140 mL

Final volume (V2) = 65 mL

Final temperature (T2) =?

V1/T1 = V2/T2

140/253 = 65/T2

Cross multiply

140 × T2 = 253 × 65

140 × T2 = 16445

Divide both side by 140

T2 = 16445 /140

T2 = 117 K

Finally, we shall convert 117 K to celcius temperature. This can be obtained as follow:

T(°C) = T(K) – 273

T2 = 117 K

T2 = 117 K – 273

T2 = –156 °C

Thus, the new temperature of the gas is –156 °C

Answer:

the water has been poulutid due to all of the construction and debris that might have flown into the water.

Explanation:

It takes 333.3 s for Oxygen to diffuses

Graham's law: the rate of effusion of a gas is inversely proportional to the square root of its molar masses or  

the effusion rates of two gases = the square root of the inverse of their molar masses:  

[tex]\rm \dfrac{r_1}{r_2}=\sqrt{\dfrac{M_2}{M_1} }[/tex]

or  

[tex]\rm M_1\times r_1^2=M_2\times r_2^2[/tex]

r₁ H₂ = 300 cm³/50 s=6 cm³/s

M₁ H₂ = 2 g/mol

M₂ O₂ = 32 g/mol

[tex]\tt 2\times 6^2=32\times r_2^2\\\\r_2^2=\dfrac{2\times 6^2}{32}=2.25\rightarrow r_2=1.5[/tex]

the diffusion time of Oxygen :

[tex]\tt r_2=\dfrac{V}{t}\\\\t=\dfrac{V}{r_2}=\dfrac{500~cm^3}{1.5~cm^3/s}=333.3~s[/tex]

Answer:

[tex]r_{NOCl}=9.28x10^{-2}M[/tex]

Explanation:

Hello!

In this case, given the balanced chemical reaction:

[tex]2 NO(g) + Cl_2(g) \rightarrow 2 NOCl(g)[/tex]

Since there is 1:2 mole ratio between chlorine and NOCl, based on the rate proportions, we can write:

[tex]\frac{1}{-1}r_{Cl_2} =\frac{1}{2}r_{NOCl}[/tex]

It means that for the formation of NOCl, we obtain:

[tex]r_{NOCl}=\frac{2}{-1}r_{Cl_2} \\\\r_{NOCl}=\frac{2}{-1}(-4.64x10^{-2}M)\\\\r_{NOCl}=9.28x10^{-2}M[/tex]

Notice that chlorine is disappearing, which means its rate is negate.

Best regards!

Answer: it blue

Explanation:

Answer:

349 L (To 3 significant figures)

Explanation:

The reaction equation is;

C9H20(l) + 14O2(g) ------> 9CO2(g) + 10H2O(g)

number of moles of nonane in 0.210 Kg = mass/molar mass

molar mass of nonane = 9(12) + 20(1) = 128 gmol-1

Hence number of moles = 0.210 * 10^3g/128 gmol-1 = 1.64 moles

If 1 mole of nonane produced 9 moles of CO2 from the balanced reaction equation;

1.64 moles of nonane will produce 1.64 * 9/1 = 14.76 moles of CO2

Now from the ideal gas equation;

PV=nRT

P = 1 atm

V= the unknown

n= 14.76

R = 0.082 atmLmol-1K-1

T = 15 + 273 = 288 K

V= nRT/P

V = 14.76 * 0.082 * 288/1

V = 348.57 L

Answer:

The answer is "4.37."

Explanation:

at [tex]0^{\circ} C\ Ka = 1.76 \times 10^{-5}[/tex]

[tex]\to pKa = - \log \ Ka[/tex]

            [tex]= - \log \ 1.76 \times 10^{-5}\\\\ = 4.75[/tex]

[tex]pH = pKa + \log \frac{[sodium \ acetate]}{[acetic \ acid]}[/tex]

      [tex]= 4.75 + \log \frac{[0.123]}{[0.291]}\\\\= 4.75+ \lg(0.422680412)\\\\=4.75-0.373987878\\\\=4.37601212\\\\=4.37[/tex]