Using Hess’s law, what is the standard enthalpy of formation of manganese (II) oxide, MnO(s)?

Answer:

B

Explanation:

hợp chất nào có khả năng là hợp chất ion cao nhất ?

A Al2O3?

B

Answer:

0.01228s⁻¹ = rate constant

Half-life = 56.4s

Explanation:

The first order reaction follows the equation:

ln[A] = -kt + ln[A]₀

Where [A] is amount of reactant after time t = 45.0%, k is rate constante and [A]₀ initial amount of reactant = 100%

ln[45%] = -k*65s + ln[100%]

-0.7985 = -k*65s

0.01228s⁻¹ = rate constant

Half-life is:

Half-life = ln2 / k

Answer:

AlCl3 + 3NaOH ———>Al(OH)3 + 3NaCl

Answer:

The pressure and the volume are inversely related in Boyle's Law. In Kinetic theory pressure is created by the collision of particles. If the volume is greater the number of collisions and pressure will be less. So volume and pressure are inversely related if the temperature and total kinetic energy is kept constant.

Explanation:

hope to help you

Answer:

[tex]4.67\times 10^{-4}[/tex]

Explanation:

Given that,

The pH of a certain orange juice is 3.33.

We need to find the +ion concentration.

We know that,

[tex]pH=-log[H^+][/tex]

So,

[tex]3.33=-log[H^+]\\\\\[H^+=10^{-3.33}\\\\=4.67\times 10^{-4}[/tex]

So, the +ion concentraion is equal to [tex]4.67\times 10^{-4}[/tex].

Answer:

Iodide> Bromide > chloride > flouride

Explanation:

During a nucleophilic substitution reaction, a nucleophilie replaces another in a molecule.

This process may occur via an ionic mechanism (SN1) or via a concerted mechanism (SN2).

In either case, the ease of departure of the leaving group is determined by the nature of the C-X bond. The stronger the C-X bond, the worse the leaving group will be in nucleophilic substitution. The order of strength of C-X bond is F>Cl>Br>I.

Hence, iodine displays the weakest C-X bond strength and it is thus, a very good leaving group in nucleophillic substitution while fluorine displays a very high C-X bond strength hence it is a bad leaving group in nucleophilic substitution.

Therefore, the ease of the use of halide ions as leaving groups follows the trend; Iodide> Bromide > chloride > flouride

Answer:

75.12 J

Explanation:

Applying,

Q = CΔT................ equation 1

Where Q = amount of heat, C = Heat capacity, ΔT = temperature rise.

From the question,

Given: C = 62.6 J/K, ΔT = 1.20°C

Substitute these values into equation 1

Q = 62.6(1.20)

Q = 75.12 J

Hence the amount of heat it absorbed is 75.12 J

Answer:

Astatine is a halogen with several isotopes that all have short half-lives.

Which of the following combinations of mass number and neutrons are possible as isotopes of astatine? Choose one or more:

i) A = 211, n = 127

ii) A = 210, n = 125

iii) A = 220, n = 134

iv) A = 207, n = 122

v) A = 209, n = 124

Explanation:

The mass number is the sum of the number of protons and the number of neutrons in an atom.[tex]A=no.of protons+no.of neutrons\\=>no.of neutrons=A-no.of protons\\[/tex]

Atomic number of At(astatine ) =85

That means it has --- 85protons.

Its mass number A=210

Hence, the number of neutrons in At are:

[tex]n=A-Z\\=>n=210-85\\=>n=125[/tex]

Second option:

ii) A=210 , n=125 is the answer.

Step 1: Represent a molecular formula.

[tex]\text{molecular formula} = (\text{CH}_{2}\text{N}_{2})_{n}[/tex]

Step 2: Calculate the empirical mass.

empirical mass = (12.0 g/mol × 1) + (1.0 g/mol × 2) + (14.0 g/mol × 2)

empirical mass = 42.0 g/mol

Step 3: Divide the molecular mass by the empirical mass.

[tex]n = \frac{\text{molecular mass}}{\text{empirical mass}}[/tex]

[tex]n = \frac{\text{126.0}}{\text{42.0}}[/tex]

[tex]n = 3[/tex]

Step 4: Multiply the subscripts by the value of n to obtain the molecular formula.

[tex]\text{molecular formula} = (\text{CH}_{2}\text{N}_{2})_{3}[/tex]

[tex]\boxed{\text{molecular formula} = \text{C}_{3}\text{H}_{6}\text{N}_{6}}[/tex]

[tex]\\[/tex]

#ILoveChemistry

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Chemistry and chemical reactions are not just limited to the laboratories but also the world around you.

Chemistry in Food Production:

Plants produce food for themselves through photosynthesis; which is a complex chemical reaction in itself. The chemical reaction that takes place in photosynthesis is the most common and vital chemical reaction. 

6 CO2 + 6 H2O + light → C 6H12O6 + 6 O2

Chemistry in Hygiene:

Right before you consume your food, you make it a point to wash your hands with soap. Isn’t it? The cleaning action of soap is based on its ability to act as an emulsifying agent. Soaps are fatty acids salts of sodium or potassium; produced by a chemical reaction called saponification. Soaps interact with the grease or oil molecule, which, in turn, results in a cleaner surface.

The Chemistry of an Onion:

Ever wondered why you shed tears while chopping an onion? This also happens because of the underlying chemistry concepts. As soon as you slice an onion, sulfenic acid is formed from amino acid sulfoxides. Sulfenic acid is responsible for the volatile gas, propanethiol S-oxide, that stimulates the production of tears in the eyes.

Chemistry in Baking:

Who does not like to eat fluffy freshly baked bread? Baking soda is an efficient leavening agent. The addition of baking soda to food items before cooking leads to the production of carbon dioxide (CO2); which causes the foods to rise. This whole process of rising of baked good is called chemical leavening.

Chemistry in Food Preservatives:

In case you ever read the ingredients on the bottle of ketchup, jams or pickles, you might be surprised to see a never-ending list of chemicals. What are they? These chemicals are called food preservatives; which delay the growth of microorganisms in foods. The chemical food preservatives not only prohibit the growth of bacteria, virus, fungi but also hinder the oxidation of fats, which is responsible for making the foods rancid. The most common chemical food preservatives are sodium benzoate, sorbic acid, potassium sorbate, calcium sorbate, sodium sorbate, propionic acid, and the salts of nitrous acid.

Chemistry in Digestion

The moment you put food in your mouth, a number of different chemical reactions start in your digestive tract. Saliva contains the enzyme amylase, which is responsible for breaking down carbohydrates, the stomach starts producing hydrochloric acid, the liver releases bile and the list of compounds released during digestion goes on. How do they work? All these enzymes undergo chemical reactions so that proper digestion, as well as assimilation of the food, occurs.

The Working of a Sunscreen

Before going out on a sunny day, you make it a point to wear sunscreen. Even the principle, behind the working of a sunscreen, has a chemistry background. The sunscreen uses a combination of organic and inorganic compounds to act as a filter for incoming ultraviolet rays. Sunblocks, on the other hand, scatter away UV light; so that it is unable to penetrate deep into the skin. Sunblocks contain complex chemical compounds like zinc oxide or titanium oxide, which prevent the UV rays to invade deeper into the skin.

Chemistry in Rust Formation

With time, your iron instruments start developing an orange-brown flaky coating called rust. The rusting of iron is a type of oxidation reaction. The atoms in the metal iron undergo oxidation and reduction; causing rusting. The formation of verdigris on copper and the tarnishing of silver are also the other everyday examples of chemical reactions. The chemical equation underlying rusting is:

Fe + O2 + H2O → Fe2O3. XH2O

Hope it helps.

Explanation:

pH is a measure of how acidic/basic water is. The range goes from 0 - 14, with 7 being neutral. pHs of less than 7 indicate acidity, whereas a pH of greater than 7 indicates a base.

Explanation:

Efficiency = (output/input)×100%

70% = output/(800 W)

which means

output = 0.70×(800 W) = 560 W

Answer:

The problem of energy exchange between waves and particles, which leads to energization of the latter, in an unstable plasma typical of the radiation belts. The ongoing Van Allen Probes space mission brought this problem among the most discussed in space physics. A free energy which is present in an unstable plasma provides the indispensable condition for energy transfer from lower energy particles to higher-energy particles via resonant wave-particle interaction. This process is studied in detail by the example of electron interactions with whistler mode wave packets originated from lightning-induced emission. We emphasize that in an unstable plasma, the energy source for electron energization is the energy of other particles, rather than the wave energy as is often assumed. The way by which the energy is transferred from lower energy to higher-energy particles includes two processes that operate concurrently, in the same space-time domain, or sequentially, in different space-time domains, in which a given wave packet is located. In the first process, one group of resonant particles gives the energy to the wave. The second process consists in wave absorption by another group of resonant particles, whose energy therefore increases. We argue that this mechanism represents an efficient means of electron energization in the radiation belts.

Explanation:

Fun facts:

In the process of energy transfer between two groups of particles both processes operate simultaneously, and if the lower energy part of plasma distribution gives energy to the wave while the higher‐energy part absorbs the wave enrgy, then the wave‐mediated energy transfer from lower energy particles to higher‐energy ...

Answer: The correct option is C (One of the fatty acid salts was unsaturated, and it completely isomerized under the reaction conditions).

Explanation:

Fats and oils belongs to a general group of compounds known as lipids. Fatty acids are weak acid and are divided into two:

--> Saturated fatty acids: These have NO double bonds in their hydrocarbon chain, and

--> Unsaturated fatty acids: These have one or more double bonds in their hydrocarbon chain.

SAPONIFICATION is defined as the process by which fats and oil is hydrolyzed with caustic alkali to yield propane-1,2,3-triol and the corresponding sodium salt of the component fatty acids. During this process, One hydroxide ion is required to hydrolyze one ester linkage of a triacylglycerol molecule. Because there are three ester linkages in a triacylglycerol, three equivalents of sodium hydroxide will be needed to completely saponify the triacylglycerol. This explains the reason why saponification of the triacylglycerol iresulted in four different fatty acid salts.

Answer:

a) Independent variable - Temperature

Dependent variable -   amount of dissolve oxygen over a 12-month period

b) Independent variable - pH

Dependent variable - solubility of SO2 in the wine

c) Independent variable - H2SO4 concentration

Dependent variable - voltage output.

Explanation:

An independent variable is the one whose value remain constant while a dependent variable is one whose values changes and is dependent on the independent variable

a) Independent variable - Temperature

Dependent variable -   amount of dissolve oxygen over a 12-month period

b) Independent variable - pH

Dependent variable - solubility of SO2 in the wine

c) Independent variable - H2SO4 concentration

Dependent variable - voltage output.

Answer:

0.287 M

Ba(OH)₂ + 2 HClO₄ ⇒ Ba(ClO₄)₂ + 2 H₂O

1.62 M

Explanation:

Step 1: Calculate the concentration of Ba(OH)₂

We will use the following expression.

[Ba(OH)₂] = mass Ba(OH)₂/ molar mass Ba(OH)₂ × liters of solution

[Ba(OH)₂] = 2.29 g/ 171.34 g/mol × 0.0466 L = 0.287 M

Step 2: Write the balanced neutralization equation

Ba(OH)₂ + 2 HClO₄ ⇒ Ba(ClO₄)₂ + 2 H₂O

Step 3: Calculate the reacting moles of Ba(OH)₂

25.5 mL of 0.287 M Ba(OH)₂ react.

0.0255 L × 0.287 mol/L = 7.32 × 10⁻³ mol

Step 4: Calculate the reacting moles of HClO₄

7.32 × 10⁻³ mol Ba(OH)₂ 2 mol HClO₄/1 mol Ba(OH)₂ = 0.0146 mol HClO₄

Step 5: Calculate the concentration of HClO₄

0.0146 moles of HClO₄ are in 8.99 mL of solution.

[HClO₄] = 0.0146 mol/0.00899 L = 1.62 M

Answer:

Draw the structures and provide the names of all the isomeric alcohols that have the molecular formula C4H10O.

Draw the structures of (a) 6-methyl-3-heptanol and (b) trans-2-methylcyclohexanol

Explanation:

Isomers are compounds with the same molecular formula but different structural arrangements of atoms.

The given molecule is:

C4H10O.

The possible isomeric alcohols structures are shown below:

Structure of (a) 6-methyl-3-heptanol:

The root word -hept indicates that the main carbon chain has seven carbons.

-ol suffix indicates the presence of alcohol functional group at third carbon.

The 6-methyl prefix indicates the presence of methyl group as the substituent at the sixth position of the main carbon chain.

The structure of 6-methyl-3-heptanol is shown below:

The structure of trans-2-methyl cyclohexanol is shown below:

Answer:

Hello There!!

Explanation:

The atom is still 24Na.

hope this helps,have a great day!!

~Pinky~

Answer:

The answer is the explanation.

Explanation:

The acetic acid, CH3COOH, reacts with calcium hydroxide, Ca(OH)2, producing acetate ion, CH3COO- and water as follows:

2CH3COOH + Ca(OH)2 → 2CH3COO- + 2H2O + Ca²⁺

That means the moles of acetic acid decrease whereas the moles of  acetate ion are increased. The ratio of [CH3COOH] / [CH3COO-] is different.

As a base is added, the concentration of H3O+ decreases increasing the pH.

That means:

TRUE A. The number of moles of CH3COOH will decrease.

FALSE B. The number of moles of CH3COO- will decrease.

TRUE C. The equilibrium concentration of H3O will decrease.

FALSE D. The pH will decrease.

FALSE E. The ratio of [CH3COOH] / [CH3COO-] will remain the same.

Answer:

Find answers below.

Explanation:

1. Boyle's law is a gas law that relates pressure and volume and states that for a fixed amount of gas at constant temperature, the pressure and volume of the gas are directly related.

Mathematically, Boyle's law is given by;

[tex] PV = K[/tex]

[tex] P_{1}V_{1} = P_{2}V_{2} [/tex]

Where;

P1 and P2 represents the initial and final pressures respectively.

V1 and V2 represents the initial and final volumes respectively.

2. Charles law is a gas law that states that for a fixed amount of gas at constant pressure, the volume of the gas is propotional to its Kelvin temperature.

Mathematically, Charles is given by;

[tex] VT = K[/tex]

[tex] \frac{V_{1}}{T_{1}} = \frac{V_{2}}{T_{2}}[/tex]

Where;

V1 and V2 represents the initial and final volumes respectively.

T1 and T2 represents the initial and final temperatures respectively.

3. Dalton law is a law that states that the total pressure of a gas mixture is equal to the sum of the partial pressure of its component gases.

4. Avogadro's law is a gas law that states that the volume of a gas is directly proportional to the number of moles of present when the pressure and temperature are held constant.

5. Gay Lussac's law is a gas law that states for a fixed amount of gas at constant volume, the pressure of the gas is directly proportional to its Kelvin temperature.

Mathematically, Gay Lussac's law is given by;

[tex] PT = K[/tex]

[tex] \frac{P1}{T1} = \frac{P2}{T2}[/tex]

6. The combined gas law is a gas law that relates pressure, volume, and temperature.

7. The ideal gas law is the equation PV = nRT

Where;

P is the pressure.

V is the volume.

n is the number of moles of substance.

R is the ideal gas constant.

T is the temperature.

Answer:

2.7 °C.kg/mol

Explanation:

Step 1: Calculate the freezing point depression (ΔT)

The normal freezing point of a certain liquid X is-7.30°C and the solution freezes at -9.9°C instead. The freezing point depression is:

ΔT = -7.30 °C - (-9.9 °C) = 2.6 °C

Step 2: Calculate the molality of the solution (b)

We will use the following expression.

b = mass of solute / molar mass of solute × kilograms of solvent

b = 102. g / (162.2 g/mol) × 0.650 kg = 0.967 mol/kg

Step 3: Calculate the molal freezing point depression constant Kf of X

Freezing point depression is a colligative property. It can be calculated using the following expression.

ΔT = Kf × b

Kf = ΔT / b

Kf = 2.6 °C / (0.967 mol/kg) = 2.7 °C.kg/mol

Answer:

Semi Metals-Boron, Silicon

Noble Gasses-Helium, Argon

Halogens-Clorine, Iodine

Transition metals-Iron, Tungsten

Alkaline earth metals-Calcium, Magnesium

Answer:

A. HCl is the limiting reactant.

B. Theoretical yield of Cl₂ is 20.9 g.

C. Actual yield of Cl₂ = 15.2 g.

Explanation:

The balanced equation for the reaction is given below:

4HCl + MnO₂ –> MnCl₂ + 2H₂O + Cl₂

Next, we shall determine the masses of HCl and MnO₂ that reacted and the mass of Cl₂ produced from the balanced equation. This can be obtained as follow:

Molar mass of HCl = 1 + 35.5

= 36.5 g/mol

Mass of HCl from the balanced equation = 4 × 36.5 = 146 g

Molar mass of MnO₂ = 55 + (2×16)

= 55 + 32

= 87 g/mol

Mass of MnO₂ from the balanced equation = 1 × 87 = 87 g

Molar mass of Cl₂ = 2 × 35.5

= 71 g/mol

Mass of Cl₂ from the balanced equation = 1 × 71 = 71 g

SUMMARY:

From the balanced equation above,

146 g of HCl reacted with 87 g of MnO₂ to produce 71 g of Cl₂.

A. Determination of the limiting reactant.

From the balanced equation above,

146 g of HCl reacted with 87 g of MnO₂.

Therefore, 42.9 g of HCl will react with = (42.9 × 87)/146 = 25.6 g of MnO₂.

From the calculation made above, we can see clearly that only 25.6 g out of 43.1 g of MnO₂ given was needed to react completely with 42.9 g of HCl.

Therefore, HCl is the limiting reactant.

B. Determination of theoretical yield of Cl₂.

Here, the limiting reactant will be used.

From the balanced equation above,

146 g of HCl reacted to produce 71 g of Cl₂.

Therefore, 42.9 g of HCl will react to produce = (42.9 × 71)/146 = 20.9 g of Cl₂.

Thus, the theoretical yield of Cl₂ is 20.9 g.

C. Determination of the actual yield of Cl₂.

Theoretical yield of Cl₂ = 20.9 g

Percentage yield of Cl₂ = 72.9%

Actual yield of Cl₂ =?

Percentage yield = Actual yield / Theoretical yield × 100

72.9% = Actual yield / 20.9

Cross multiply

Actual yield = 72.9% × 20.9

Actual yield = 72.9/100 × 20.9

Actual yield = 0.729 × 20.9

Actual yield of Cl₂ = 15.2 g

Answer:

Explanation:

The most highly stable cycloalkane is cyclohexane. It does not suffer from an angle or torsional strain, and it has the appropriate stability as chain alkanes. Because of the peculiar conformation it takes, this stability leads to the cyclohexane conformation popularly known as the "chair" conformation.

However, from the information given;

The chair conformation structure of  trans-1-bromo-3-methylcyclohexane is carefully drawn and the substituents are appropriately attached in the image below.

Answer:

pH = 9.54.

Explanation:

Hello there!

In this case, since this is an acidic buffer due to the hydrocyanic acid, it will be firstly necessary for us to calculate the moles of both acid and conjugate base in 150 mL given their concentrations:

[tex]n_{acid}=0.472mol/L*0.150L=0.0708mol\\\\n_{base}=0.342mol/L*0.150L=0.0513mol[/tex]

Next, since the effect of adding NaOH, consume the acid and produce more base, we subtract 0.0194 moles from 0.0708 mol and add 0.0194 to 0.0513 mol for us to calculate the new moles:

[tex]n_{acid}^{new}=0.0708mol-0.0194mol=0.0514mol\\\\n_{base}^{new}=0.0513mol+0.0194mol=0.0707mol[/tex]

Thus, since the pKa of hydrocyanic acid is 9.40, we therefore use the Henderson-Hasselbach equation to calculate the pH of the resulting solution for the same volume:

[tex]pH=9.40+log(\frac{0.0707mol}{0.0514mol} )\\\\pH=9.54[/tex]

Which increase make sense since we added some strong base.

Regards!

Answer:

pH = 8.87

Explanation:

Hydroiodic acid, HI, is a strong acid that reacts with ammonia, NH3, to produce ammonium ion, NH⁴⁺. That means the moles of HI added = moles of NH3 consumed and moles of NH4⁺ produced.

Initial moles NH₄⁺:

0.225L * (0.298mol/L) = 0.06705 moles

Initial moles NH3:

0.225L * (0.478mol/L) = 0.10755 moles

After the reaction the moles are:

0.10755moles NH3 - 0.0560moles = 0.05155 moles NH3

0.06705moles NH4+ + 0.0560moles = 0.12305 moles NH4+

Using H-H equation for weak bases:

pOH = pKb + log ([NH4+] / [NH3])

pKb for ammonia is 4.75, [NH4+] could be the moles of NH4+ = 0.12305mol,

[NH3] = 0.05155moles

Replacing:

pOH = 4.75 + log (0.12305mol / 0.05155moles)

pOH = 5.13

pH = 14-pOH

Answer:

F-

Explanation:

Since Fluorine needs one more electron to reach a full octet, it takes in 1 more electron to become an anion. Therefore, with the extra negative charge from the 1 electron, a Fluoride ion has a charge of -1.

Hope this helped!

Answer:

F_

Explanation:

the symbol or formula

is F_

Answer:

A. How the concentration of the reactants affects the rate of a reaction

Explanation:

Let's consider a generic reaction.

A + B ⇒ Products

The generic rate law is:

rate  = k × [A]ᵃ × [B]ᵇ

where,

As we can see, the rate law shows how the concentration of the reactants affects the rate of a reaction.

Answer:

compounds are elements include an element and a compound

Explanation:

elements in the decomposition reaction is the substance that cannot be separated into simpler substances. Compounds, technically act as a reactant in the decomposition reaction, but since the reaction breakdown one substance into two or more, sometimes it exists in the product