Calculate the enthalpy change for the thermite reaction: 2al(s)+fe2o3(s)→2fe(s)+al2o3(s), δh∘rxn=−850 kj when 10.0 mol of al undergoes the reaction with a stoichiometrically equivalent amount of fe2o3.

Answer:

True

Explanation:

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To calculate mass of  Fe₂O₃ we need to apply concept of stoichiometry. So according to this we need molar mass of  Fe₂O₃, mole ratio of  Fe₂O₃ to C. Therefore the mass of  Fe₂O₃ required to react with  19.0 g C is  67.4g.

Stoichiometry is a part of chemistry that help us in making relationship between reactant and product from quantitative aspects.

The balanced equation is

2Fe₂O₃+3C [tex]\rightarrow[/tex]  3CO₂+4Fe

The molar ratio of Fe₂O₃ to carbon is 2:3

2 moles of Fe₂O₃ needed to react with 3 moles of carbon

3 mole of carbon needed= 2 mole of Fe₂O₃

1 mole of carbon needed = 2÷3 mole of Fe₂O₃

(19÷12) = 1.58 mole of carbon needed=  (2÷3 )× 1.58 mole= 0.422 mole of  Fe₂O₃

mass of  Fe₂O₃  = moles of  Fe₂O₃ ×Molar mass of  Fe₂O₃

                           = 0.422 mole×159.70

                           = 67.4g

Therefore the mass of Fe₂O₃ required to react with  19.0 g C is 67.4g

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To convert the moles of Fe₂O₃  to grams using its molar mass.

To calculate the number of grams of Fe₂O₃ needed to react with 19.0 g C, we need to use the stoichiometric mole ratio from the balanced chemical equation. First, convert the given mass of C to moles using its molar mass. Then, use the mole ratio from the equation Fe₂O₃+ 3CO -> 2Fe + 3CO₂ to determine the moles of Fe₂O₃ needed. Finally, convert the moles of Fe₂O₃ to grams using its molar mass.

Given: 19.0 g C
Calculate: grams of Fe₂O₃

Therefore, 83.8 grams of Fe₂O₃ are needed to react with 19.0 grams of C.

Explanation:

Relation between freezing temperature and molal concentration is as follows.

          [tex]\Delta T_{f} = k_{f} \times m[/tex]

The given data is as follows.

    [tex]\Delta T_{f}[/tex] = difference in temperature = [tex][0 - (-2.75)]^{o}C[/tex] = [tex]2.75^{o}C[/tex]

      [tex]k_{f} = 1.86^{o}C/mol[/tex]

            molality, (m) = ?  

Now, putting the given values into the above formula as follows.

                m = [tex]\frac{\Delta T_{f}}{k_{f}}[/tex]

                    = [tex]\frac{2.75^{o}C}{1.86^{o}C/mol}[/tex]

                    = 1.48 m

Therefore, we can conclude that molal concentration of glucose in the given solution is 1.48 m.

Ionization energy is the property of an atom that describes the ease with which an atom gives up an electron to form a positive ion.

The ionization energy of a chemical element is expressed in joules or electron volts. It is commonly measured inside an electric discharge tube where fast-moving electrons are generated due to an electric current collision with a gaseous atom of the element.

This causes the ejection of one of its electrons. In the case of a hydrogen atom, which has only one orbiting electron which is in turn bound to a nucleus with only one proton, the ionization energy of 2.18 × 10^−18 joule or 13.6 electron volts is needed to move the electron from its lowest energy level out of the atom.

The ionization energy magnitude is dependent on the element and the combined effects of the electric charge of its nucleus, atomic size, and also its electronic configuration. Electron removal is also the hardest for noble gases and easiest for alkali metals.

The ionization energy required for the removal of electron removal is the hardest as the electron number decreases progressively. Because as the atom loses electrons, the positive charge on the nucleus of the atom does not change; thus, as each electron is removed, the remaining ones are held more firmly.

Therefore, Ionisation energy is the property of an atom that describes the ease with which an atom gives up an electron to form a positive ion.

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The strongest intermolecular force between bromine (Br2) and carbon tetrachloride (CCl4) when Br2 is dissolved in CCl4 is the London dispersion force, as both compounds are nonpolar.

The strongest type of intermolecular force between solute and solvent in a mixture of Br2(l) dissolved in CCl4(l) is likely the London dispersion force. Both Br2 and CCl4 are nonpolar molecules, which means they lack a permanent dipole moment. Consequently, they do not exhibit dipole-dipole interactions. However, due to the temporary fluctuations in electron density within these molecules, instantaneous dipoles can be induced, giving rise to London dispersion forces, which are the only significant intermolecular force between the two substances.

Generally, London dispersion forces increase with the size and number of electrons in the molecule, leading to greater interactions. Bromine (Br2) and carbon tetrachloride (CCl4) both have a relatively large number of electrons and molecular masses, thus contributing to the strength of their dispersion forces.

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Answer :

(1) The time passed by the sample is [tex]2.4\times 10^3\text{ years}[/tex]

(2) The amount left after decay process is 1.14 mmol.

Explanation :

Part 1 :

Half-life = 5730 years

First we have to calculate the rate constant, we use the formula :

[tex]k=\frac{0.693}{t_{1/2}}[/tex]

[tex]k=\frac{0.693}{5730\text{ years}}[/tex]

[tex]k=1.21\times 10^{-4}\text{ years}^{-1}[/tex]

Now we have to calculate the time passed.

Expression for rate law for first order kinetics is given by:

[tex]t=\frac{2.303}{k}\log\frac{a}{a-x}[/tex]

where,

k = rate constant  = [tex]1.21\times 10^{-4}\text{ years}^{-1}[/tex]

t = time passed by the sample  = ?

a = let initial amount of the reactant  = 100 g

a - x = amount left after decay process = 100 - 25 = 75 g

Now put all the given values in above equation, we get

[tex]t=\frac{2.303}{1.21\times 10^{-4}}\log\frac{100}{75}[/tex]

[tex]t=2377.9\text{ years}=2.4\times 10^3\text{ years}[/tex]

Therefore, the time passed by the sample is [tex]2.4\times 10^3\text{ years}[/tex]

Part 2 :

Now we have to calculate the amount left.

Expression for rate law for first order kinetics is given by:

[tex]t=\frac{2.303}{k}\log\frac{a}{a-x}[/tex]

where,

k = rate constant  = [tex]1.21\times 10^{-4}\text{ years}^{-1}[/tex]

t = time passed by the sample  = 2255 years

a = let initial amount of the reactant  = 1.5 mmol

a - x = amount left after decay process = ?

Now put all the given values in above equation, we get

[tex]2255=\frac{2.303}{1.21\times 10^{-4}}\log\frac{1.5}{a-x}[/tex]

[tex]a-x=1.14mmol[/tex]

Therefore, the amount left after decay process is 1.14 mmol.

The specific heat capacity of the metal is calculated using the formula q=mcΔT. With the provided information (1495 J of heat, 337 g of metal, temperature change from 55.0°C to 66.0°C), the specific heat capacity is found to be 0.399 J/g°C.

To calculate the specific heat capacity of the metal, we can use the formula q = mcΔT, where q is the heat absorbed or released (in joules), m is the mass of the substance (in grams), c is the specific heat capacity (in J/g°C), and ΔT is the change in temperature (in °C).

Given that 1495 J of heat is needed to raise the temperature of a 337 g sample of a metal from 55.0°C to 66.0°C, we have:

ΔT = 66.0°C - 55.0°C = 11.0°C
q = 1495 J
m = 337 g

Plugging these values into the formula, we can solve for c:

1495 J = (337 g)(c)(11.0°C)
c = 1495 J / (337 g × 11.0°C)
c = 0.399 J/g°C

Thus, the specific heat capacity of the metal is 0.399 J/g°C.

2) So, after every period of one half-life the concentration of the reactant will decrease by half.

Based on the number of half-lives undergone by the substance,  the mass of the substance remaining after three half-lives is 2.25 g.

The half-life of a substance is the time it will take for half the amount of the substance to decay or decompose.

The initial mass of the substance is 18.0 g

The substance undergoes three half-lives.

After the first half-life, mass remaining = 18/2 = 9.0 g

After the first half-life, mass remaining = 18/2 = 9.0 g

After the third half-life, mass remaining = 4.5/2 = 2.25 g

Therefore, the mass of the substance remaining after three half-lives is 2.25 g.

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Answer:

They undergo photosynthesis which makes the carbon dioxide to be used rather than produced.

Explanation:

Hello,

Forests are widely known as the "Earth's lungs" due to the photosynthesis that vegetable life constantly perform as the carbon dioxide that is in the environment is used by them to produce energy, glucose and oxygen considering such metabolic pathway. Now, forest act as carbon sinks as the proportion between carbon dioxide consumers to producers is by far greater than 1 as long as there are more plants that use higher amounts of carbon dioxide than those that are released during the respiration of animals or any other natural process producing carbon dioxide.

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Answer: Option (A) is the correct answer.

Explanation:

When a gas is heated then its molecules gain more amount of kinetic energy. And, as kinetic energy is the energy obtained by an object due to its motion.

Therefore, with increase in kinetic energy of molecules of the gas there will occur more number of collisions. Hence, the gas will move more rapidly from one place to another.

Therefore, upon heating of a gas the energy absorbed by the gas will get converted into kinetic energy due to which gas move much more rapidly.

Potential energy is the energy obtained by an object due to its position and not because of its movement.

Thus, we can conclude that when a gas is heated all of the absorbed energy is converted to kinetic energy.

The pH of a sodium acetate (NaC2H3O2) solution can be calculated using the equilibrium expression for the base hydrolysis reaction of the acetate ion.

The pH of a sodium acetate (NaC2H3O2) solution can be calculated using the equilibrium expression for the base hydrolysis reaction of the acetate ion:

CH3CO2⁻ + H2O ⇌ CH3CO2H + OH⁻

This reaction is the reverse of the ionization reaction for acetic acid. The Kb value for the acetate ion is calculated as Kw/Ka, where Ka is the acid dissociation constant for acetic acid, given as 1.8 × 10⁻⁵ at 25.0 °C. To find the pH, we need to calculate the concentration of hydroxide ions (OH⁻) in the solution.

The hydroxide ion concentration can be calculated using the equation [OH⁻] = √(Kb × [CH3CO2H]). Given that the concentration of acetate ion [CH3CO2⁻] is equal to the initial concentration of sodium acetate, and assuming complete dissociation of sodium acetate in water, the concentration of acetic acid [CH3CO2H] will be equal to the initial concentration of sodium acetate. Therefore, [OH⁻] = √(Kb × [NaC2H3O2]). Finally, the pH of the solution can be calculated as -log[OH⁻].

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The solution is basic due to its high hydroxide ion concentration. The pOH obtained should be around -0.748.

To determine the pOH of a 2.80 M Ba(OH)₂ solution, calculate the hydroxide ion concentration and find its negative logarithm.

To find the pOH of a 2.80 M Ba(OH)₂ solution, follow these steps:

Determine the concentration of OH- ions produced by Ba(OH)₂. Since each Ba(OH)₂ molecule dissociates into one Ba²⁺ ion and two OH⁻ ions, the concentration of OH⁻ ions will be twice the concentration of Ba(OH)₂.

Therefore, [OH⁻] = 2 × 2.80 M = 5.60 M.

Calculate the pOH by taking the negative logarithm of the hydroxide ion concentration: pOH = -log(5.60).

Using the logarithm function, pOH = -log(5.60) ≈ -0.748.

However, the pOH value less than zero is not realistic, indicating very high basicity. Generally, the practical range considers the pOH to lie between 0 and 14.

Since a high [OH⁻] concentration results in a very low pOH, we can conclude that the solution is basic.

Final answer:

Carbon monoxide and carbon dioxide both contain carbon and oxygen atoms. CO has one oxygen atom with a triple bond to carbon, whereas CO2 has two oxygen atoms, each with a double bond to carbon. CO is toxic while CO2 contributes to global climate change.

Explanation:

The chemical composition of carbon monoxide (CO) is similar to that of carbon dioxide (CO2) in that both compounds consist of carbon (C) and oxygen (O) atoms. However, the key difference is in the number of oxygen atoms. CO has one oxygen atom, while CO2 has two oxygen atoms. The molecular structures of both compounds reveal these differences. CO has a triple bond between the carbon and the oxygen atom, which includes two covalent bonds and one dative covalent bond. In contrast, the CO2 molecule has a linear structure with a double bond to each oxygen atom, forming an O=C=O configuration.

In terms of Lewis structures, CO's Lewis structure consists of a carbon atom triple-bonded to an oxygen atom with a lone pair on the oxygen, while CO2's Lewis structure displays the carbon atom with two double bonds, each connected to an oxygen atom with two sets of lone pairs.

Both CO and CO2 are important in context as they have significant environmental and health impacts. Carbon monoxide is a toxic gas with the potential to bind to hemoglobin, making it a competitive inhibitor for oxygen transport in the bloodstream. Carbon dioxide, while non-toxic at normal concentrations, is a significant greenhouse gas contributing to global climate change.

The statement comparing mitosis and meiosis accurately indicates that mitosis results in two identical diploid cells, whereas meiosis produces four genetically distinct haploid cells.

The correct statement that compares mitosis and meiosis is:

A) The result of mitosis is two identical diploid cells. The result of meiosis is four genetically different haploid cells.

Both processes are preceded by one round of DNA replication. However, while mitosis includes one cellular division resulting in two identical diploid cells, meiosis includes two nuclear divisions which result in four genetically distinct haploid cells. Mitosis is essential for growth and repair, and meiosis provides genetic diversity through sexual reproduction.

Answer: The molecular equation is written below.

Explanation:

Every balanced chemical equation follows law of conservation of mass.

Law of conservation of mass states that mass can neither be created nor be destroyed but it can only be transformed from one form to another form.

This also means that total mass on the reactant side must be equal to the total mass on the product side.

A molecular equation is the balanced chemical equation where the ionic compounds are expressed as molecules rather than constituent ions.

The chemical equation for the reaction of copper (II) chloride and potassium phosphate follows:

[tex]3CuCl_2(aq.)+2K_3PO_4(aq.)\rightarrow Cu_3(PO_4)_2(s)+6KCl[/tex]

By Stoichiometry of the reaction:

3 moles of copper (II) chloride reacts with 2 moles of potassium phosphate to produce 1 mole of copper (II) phosphate and 6 moles of potassium chloride.

Hence, the molecular equation is written above.

The pH and pOH of 6.6g of NaOH in 100mL solution are -0.217 and 14.217 respectively

Data;

To find the pOH and pH of this solution, we have to know the molarity of this solution.

Molarity = number of moles of solute / volume of the solution

number of moles of the solute = mass / molar mass

molar mass of NaOH = 40g/mol

number of moles = 6.6/40 = 0.165moles

Molarity of this solution is

[tex]M = \frac{number of moles }{volume of solution}\\M = \frac{0.165}{0.1}\\ Molarity = 1.65M[/tex]

[tex]pOH= -log[OH^-]\\pOH = -log[1.65]\\pOH = -0.217[/tex]

At 25°C, the pOH of NaOH is -0.217, let's calculate the pH

[tex]pOH+pH=14\\-0.217+pH=14\\pH=14-(-0.217)\\pH=14.217[/tex]

From the calculations above, the pH and pOH of 6.6g of NaOH in 100mL solution are -0.217 and 14.217 respectively.

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The number of moles of NaOH in the solution is 0.165 mol and its molarity is 1.65 M. The pOH of the solution is -0.217 and the pH is 14.217.

The mass of Sodium Hydroxide present in the solution is 6.6 g. The molar mass of Sodium Hydroxide (NaOH) is approximately 40 g/mol. Therefore, the number of moles present in the solution can be calculated by dividing the mass by the molar mass. So, the number of moles = 6.6/40 = 0.165 mol.

The volume of the solution is 100 ml or 0.1 L. The molarity of the solution can be found by dividing the number of moles by the volume in liters which gives us, Molarity = 0.165/0.1 = 1.65 M.

Because NaOH is a strong base, in water it dissociates completely to form hydroxide ions (OH-). Hence, the molarity of OH- is the same as the molarity of NaOH i.e., 1.65 M. In order to find the pOH we can use the formula -log[OH-], hence the pOH= -log(1.65) = -0.217.

The relationship between pH and pOH at 25 °C is given by the expression, pH + pOH = 14. Therefore, the pH can be calculated as follows, pH = 14 - pOH = 14 - (-0.217) = 14.217.

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