27. Which is true about scientific theories? (2 points)
They are the result of a single experiment.
They are the results of many experiments over a long period of time.
O They are proposed by scientists who wish to investigate a new topic.
They are only based on the most recent evidence.

All elements have a AHf, of 0

kJ/mole at standard temperature and pressure.

An element can be defined as a substance which cannot be split into two or more simpler forms by an ordinary chemical process

Below are the list of the first twenty elements:

So therefore, all elements have a AHf, of 0

kJ/mole at standard temperature and pressure.

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Answer:

2 the mass is greater than 10.0gram

Explanation:

2 the mass is greater than 10.0gram

The major product formed will be : 2-aminophenyl ethyl ketone

The NO₂ group (-nitro group) on reduction will form a NH₂ group (-amino group).

Titration is a technique for determining unknown molarity of acid by adding a base of know malarkey to a known volume of acid

The process of calculating the quantity of a material A by adding measured increments of substance B, the titrant, with which it reacts until exact chemical equivalency is obtained " is the definition of titration. Titration, commonly referred to as titrimetry, is a method of chemical qualitative analysis used to determine the concentration of a certain analyte in a mixture.

The goal of titration is to identify the equivalence point, or the point at which chemically equivalent amounts of the reactants have been combined, which is a key analytical chemistry technique also known as volumetric analysis. The stoichiometry of the reactants determines how many reactants have been mixed at the equivalence point.

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The equation for the dissociation of iron (iii) nitrate is given below:

A dissociation equation is an equation in which a compound separates into the constituent ions present in the compound.

The equation for the dissociation of iron (iii) nitrate is given below:

Fe₂(NO₃)₃ (aq) ⇄  2 Fe⁺ (aq) + 3 NO₃⁻ (aq)

In conclusion, the dissociation of iron(iii) nitrate produces iron (ii) ions and nitrate ions.

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74.4 mL of a 0.8 M solution of citric acid would be needed to react with 15 grams of baking soda.

Equation that demonstrates reaction;

C6H8O7 + 3NaHCO3 → Na3C6H5O7 + 3H2O + 3CO2

Molar mass of citric acid (C6H8O7) =  12×6 + 1.008×8 + 16×7

                                                           =  192.064 g/mol

Molar mass of baking soda (NaHCO3) = 23 + 1 + 12 + 3×16

                                                                = 84 g/mol

[tex]^c C_6H_8O_7 = 0.8 M = 0.8 mol/L\\^m NaHCO_3 =15g[/tex]

From the reaction equation:

[tex]3[/tex] × [tex]^n C_6H_8O_7 = ^n NaHCO_3[/tex]

Molar mass of baking soda (NaHCO3) = 84 g/mol

So,

[tex]^n NaHCO_3 = ^m NaHCO_3/ ^MNaHCO_3[/tex]

And;

[tex]^n C_6H_8O_7 = ^nNaHCO_3/ 3[/tex]

From the definition of Molarity,

[tex]^V C_6H_8O_7 =\frac{^n C_6H_8O_7}{^cC_6H_8O_7 } =\frac{^n NaHCO_3}{^3*n^cC_6H_8O_7 } = \frac{^m NaHCO_3 / ^M NaHCO^3}{3*^cC_6H_8O_7 }[/tex]

Calculating;

[tex]^V C_6H_8O_7 = \frac{15/84}{3*0.8} \\[/tex]

               [tex]= 0.0744L\\= 74.4 mL[/tex]

Therefore, 74.4 mL of a 0.8 M solution of citric acid would be needed to react with 15 grams of baking soda.

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A mathematical function known as an orbital is used to describe the wave-like behavior of an electron, an electron pair, or (less frequently) nucleons.

Atomic orbitals outline the potential locations of electrons within an atom. In molecules, molecular orbitals play the same function.

Each atomic orbital has three quantum numbers, n, l, and ml, attached to it. The wave function was used to calculate these numbers.

The square of the wave function 2 can be used to calculate the size and form of an orbital.

All atomic orbitals are centered on the atomic nucleus and have unique forms.

The s, p, and d orbitals—orbitals that correspond to the s, p, and d subshells—are the orbitals that are most frequently encountered in introductory quantum chemistry.

F orbitals can be found in the ground states of heavier atoms as well.

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Answer:

In chemistry, an orbital is related to also a wave function. An Orbital is a practical region or part that is around the nucleus in a molecule and maybe an atom. It can contain up to two electrons, electrons form themselves around the nucleus.

Explanation:

No Explanation

Taking into account the reaction stoichiometry, 3.63 moles of NH₃ will be produced if 50.8 g N₂ reacts with 187.3 g H₂.

In first place, the balanced reaction is:

3 H₂ + N₂ → 2 NH₃

By reaction stoichiometry (that is, the relationship between the amount of reagents and products in a chemical reaction), the following amounts of moles of each compound participate in the reaction:

The molar mass of the compounds is:

Then, by reaction stoichiometry, the following mass quantities of each compound participate in the reaction:

The limiting reagent is one that is consumed first in its entirety, determining the amount of product in the reaction. When the limiting reagent is finished, the chemical reaction will stop.

To determine the limiting reagent, it is possible to use a simple rule of three as follows: if by stoichiometry 6 grams of H₂ reacts with 28 grams of N₂, 187.3 grams of H₂ reacts with how much mass of N₂?

[tex]mass of N_{2} =\frac{187.3 grams of H_{2} x28 grams of N_{2}}{6 grams of H_{2}}[/tex]

mass of N₂= 874.067 grams

But 875.087 grams of N₂ are not available, 50.8 grams are available. Since you have less mass than you need to react with 187.3 grams of H₂, N₂ will be the limiting reagent.

Considering the limiting reagent, the following rule of three can be applied: if by reaction stoichiometry 28 grams of N₂ form 2 moles of NH₃, 50.8 grams of N₂ form how many moles of NH₃?

[tex]moles of NH_{3} =\frac{50.8 grams of N_{2} x2 moles of NH_{3} }{28 grams of N_{2}}[/tex]

moles of NH₃= 3.63 moles

Finally, 3.63 moles of NH₃ will be produced if 50.8 g N₂ reacts with 187.3 g H₂.

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Answer:

Hydrolysis of 1-cyano-methylbenzene is an addition reaction while that of 1-cyano-4-methylbenzene is a substitution substitution reaction.

Explanation:

substitution reactions occur in preference to addition reactions

Answer:

298-273 = 25°C is correct answer!

Answer:

0.382 atm

Explanation:

In order to find the pressure, you need to know the moles of carbon dioxide (CO₂) gas. This can be found by multiplying the mass (g) by the molar mass (g/mol) of CO₂. It is important to arrange the conversion in a way that allows for the cancellation of units.

Molar Mass (CO₂): 12.011 g/mol + 2(15.998 g/mol)

Molar Mass (CO₂): 44.007 g/mol

15 grams CO₂               1 mole
----------------------  x  ------------------------  =  0.341 moles CO₂
                                44.007 grams

To find the pressure, you need to use the Ideal Gas Law equation.

PV = nRT

In this equation,

-----> P = pressure (atm)

-----> V = volume (L)

-----> n = moles

-----> R = Ideal Gas Constant (0.08206 atm*L/mol*K)

-----> T = temperature (K)

After you convert Celsius to Kelvin, you can plug the given and calculated values into the equation and simplify to find the pressure.

P = ? atm                              R = 0.08206 atm*L/mol*K

V = 20 L                               T = 0 °C + 273.15 = 273.15 K

n = 0.341 moles

PV = nRT

P(20 L) = (0.341 moles)(0.08206 atm*L/mol*K)(273.15 K)

P(20 L) = 7.64016

P = 0.382 atm

The amount of potassium chloride (KCl) in 27.2 kg of a solution containing 18.7% KCl by mass solution is 5.086 kg.

Mass of solute = Mass percent of solute x  Mass of the solution

Here,

Mass percent of solute = 18.7 %

Mass of the solution = 27.2 kg

Now put the value in above formula we get

Mass of solute = Mass percent of solute x  Mass of the solution

                         = [tex]\frac{18.7}{100} \times 27.2\ kg[/tex]

                         = [tex]\frac{508.64}{100}[/tex]

                         = 5.086

Thus from the above conclusion we can say that The amount of potassium chloride (KCl) in 27.2 kg of a solution containing 18.7% KCl by mass solution is 5.086 kg.

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The properties are given below:

The property of solids, liquids, and gases refers to those features which are used to identify solids, liquids and gases.

Some property of solids, liquids and gases are shape and volume.

Shape: Solids have definite shape; liquids take the shape of their container; gases have no shape.

Volume: Solids have definite volume; liquids have definite volume; gases do not have a definite volume

In conclusion, solids, liquids and gases have unique properties in their shape and volume.

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883.15 gm of Ni is produced in solution by passing a current of 67 Ampere through a period of 14 hours.

Current, I = 67 A

Time, t = 14 h = (14×60×60) s

Now total Charge passed , Q = I t = 67×14×60×60 = 3376800 C

moles of electrons passed = [tex]\frac{Q}{96500}[/tex][tex]=\frac{3376800}{96500}=34.992[/tex] mole  e⁻

34.992 moles of e⁻ will produce 34.992 /2 = 17.49 mole Ni

Now we have the reaction

Ni ²⁺ + 2e⁻ → Ni

34.992 moles of e⁻ produces 17.49 mole of Ni

mass of Ni produced = molar mass of Ni × moles of Ni = 58.693 × 17.49 = 1026.91 gm of Ni produced

But the cell is 86% efficient.

Therefore, Ni produced = 0.86×1026.91 =  883.15 gm

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The theoretical yield of H₂S is 13.5 g.

The percent yield is 75.5 %.

The equation of the reaction is given below:

Moles of FeS reacting = mass/molar mass

Molar mass of FeS = 88 g/mol

Moles of FeS reacting = 35/88 = 0.398 moles

Moles of H₂S produced = 0.398 moles

Molar mass of H₂S = 34 g/mol

Mass of H₂S produced = 0.398 * 34 = 13.5 g

Theoretical yield of H₂S is 13.5 g.

Actual yield of H₂S = 10.2 g

Percent yield = 10.2/13.5 * 100%

Percent yield = 75.5 %

In conclusion, the actual yield is less than the theoretical yield.

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Answer:

Mg(s) = oxidized

H₂SO₄(aq) (hydrogen) = reduced

Explanation:

Oxidized substances lose electrons and see an increase in oxidation number. Reduced substances gain electrons and see a decrease in oxidation number.

Lone elements always have an oxidation number of 0. H₂SO₄ and MgSO₄ are ionic compounds that can be broken up into a cation and polyatomic anion. The anion, SO₄²⁻, has an overall oxidation number of -2. Therefore, to make the overall charge of the ionic compound neutral, the hydrogen in H₂SO₄ has an oxidation state of +1 (bc there are two hydrogens) and the magnesium in MgSO₄ has an oxidation state of +2.

Since Mg(s) is losing electrons (goes from 0 to +2), it is being oxidized. Since the hydrogen in H₂SO₄(aq) is gaining electrons (goes from +1 to 0), it is being reduced.

The balanced neclear equation for alpha emission will be:

[tex]88Ra^2^2^3 --- > 86Rn^2^1^9 + 2He^4[/tex]

Radioactive decay occurs when unstable isotopes have their nuclei ruptured due to atomic instability. To understand why an isotope disintegrates, we need to look at the atomic nucleus. It is known that the nucleus is loaded with positive particles (protons), and that these are very close to each other. It is also true that particles with equal charges repel each other. Therefore, the proximity of the protons causes them to start to repel each other, in an attempt to take up as much space as possible. In view of this, the nucleus breaks, as it cannot bear these repellent charges.

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Answer:

7.88 x 10²² formula units CuCl₂

Explanation:

To find the amount of formula units, you need to (1) convert grams to moles (via the molar mass) and then (2) convert moles to formula units (via Avogadro's Number). It is important to arrange the conversions in a way that allows for the cancellation of units. The final answer should have 3 sig figs to match the sig figs of the given value.

Molar Mass (CuCl₂): 134.45 g/mol

Avogadro's Number:

6.022 x 10²³ formula units = 1 mole

17.6 g CuCl₂            1 mole             6.022 x 10²³ formula units
--------------------  x  -----------------  x  ------------------------------------------  =  
                               134.45 g                           1 mole

=  7.88 x 10²² formula units CuCl₂

Cylinder will expand to 6.08 Lit by assuming that all the energy released is converted to work used to push the piston.

Concept of work :If we  apply force on an object and if the object moves and changes it's position, then product of the force and the displacement of an object in the direction of applied force is called work.

Given,

Pressure= P= 738.52 mm Hg = 0.97 atm. (∵ 760 mm Hg = 1 atm)

Initial volume =V1= 1.7 L

Work done = W = 439.6 J

As we need our answer in litters ..

let's convert the work done into suitable units

∴work done = W = 4.26 L-atm (∵ 1 J = 101.3 L-atm)

As given all the energy is assumed to converted into work so we need not to worry About heat loss or entropy.

work done = pressure * difference in volume

W = PΔV

ΔV = 4.26÷ 0.97

∴ΔV = 4.38 LIt

There for, the volume expanded = 4.38 Lit

So, total volume = 4.38+ 1.7 = 6.08 Lit.

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From the calculation, the concentration of the oxonium ions is 1 * 10^-6 M

The term concentration refers to the amount of substances present in the solution. There are several units that can be used to show the concertation of a substances such as moles/liter, gram per liter, parts per billion, parts per billion, percentage etc.

Now we know that water is composed of the hydrogen and the hydroxide ions and the product of the both is generally known as the ion product of water and have a value of 1 * 10^-14.

If that be the case, we are in order to write the expression;

[H3O+]  [OH-] = 1 * 10^-14

[H3O+] = 1 * 10^-14/ [OH-]

[H3O+] = 1 * 10^-14/ 1 x 10^ -8

[H3O+] = 1 * 10^-6 M

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[tex]K_{sp}[/tex] of the compound is found to be  5.04 ×[tex]10^{-10}[/tex].

Solubility :Solubility can be define as the amount of a substance that dissolves or mixes in a given amount of solvent at specific conditions.

Solubility equilibrium

Ksp = [tex][A^{+} ]^{a}[/tex] [tex][B^{-} ]^{b}[/tex]

Ksp = solubility product constant

A+ = cation in an aquious solution

B- = anion in an aqueous solution

a, b = relative concentrations of a and b

Given,

Solubility = s = 3.60 × [tex]10^{-2}[/tex] g/L

molar mass = 288 g/ mol

∴ s= 3.60 × [tex]10^{-2}[/tex] g/L ÷ 288 g/ mol = 1.25 ×[tex]10^{-4}[/tex] mol/ L

Reaction:

MX3 ⇄ M + 3X

           s       3s

[tex]K_{sp}[/tex] =[ [tex]M^{+3}[/tex]] [ [tex]X^{-1}[/tex][tex]]^{3}[/tex] = solubility product

∴ [tex]K_{sp}[/tex] =[tex][s]^{} [3s]^{3}[/tex]

∴ [tex]K_{sp}[/tex] = 3 [tex]s^{4}[/tex]

∴ [tex]K_{sp}[/tex] = 3 × (3.60 × [tex]10^{-2}[/tex] [tex])^{4}[/tex]

∴ [tex]K_{sp}[/tex] = 503.8848 ×[tex]10^{-8}[/tex]  = 5.04 ×[tex]10^{-10}[/tex]

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The sun sending out electromagnetic waves is best describes the source of radiation heat.

Radiation heat is the form of electromagnetic waves.

Radiation heat, commonly referred to as thermal radiation, is the electromagnetic radiation that defines how photons exchange heat. The technique of heat transfer known as radiant heat does not require a medium to be propagated in.

Two molecules colliding with each other produce kinetic energy, moving objects have kinetic energy. Radiation heat is thermal energy. Sun directly sends thermal radiation through electromagnetic waves.

Hence , The sun sends out electromagnetic waves directly is best describes the source of radiation heat.

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Answer:

28.0 grams CsF

Explanation:

To find the mass of CsF, you need to (1) convert grams CsXeF₇ to moles CsXeF₇ (via molar mass), then (2) convert moles CsXeF₇ to moles CsF (via mole-to-mole ratio from equation coefficients), and then (3) convert moles CsF to grams CsF (via molar mass). It is important to arrange the ratios/conversions in a way that allows for the cancellation of units. The final answer should have 3 sig figs to match the sig figs of the given value.

Molar Mass (CsF): 132.91 g/mol + 18.998 g/mol

Molar Mass (CsF): 151.908 g/mol

Molar Mass (CsXeF₇): 132.91 g/mol + 131.29 g/mol + 7(18.998 g/mol)

Molar Mass (CsXeF₇): 397.186 g/mol

1 CsF + XeF₆ -----> 1 CsXeF₇

73.1 g CsXeF₇             1 mole                 1 mole CsF              151.908 g
----------------------  x  --------------------  x  ------------------------  x  ------------------  =
                                  397.186 g           1 mole CsXeF₇             1 mole

=  27.958 g CsF

=  28.0 g CsF

The enthalpy change of the reaction:  A + 2B → C is determined as follows: ΔH = ΔH₁ +  ΔH₂; option C

Enthalpy change refers to the change in heat content as reactant molecules combine to form products.

The enthalpy change of a multistep reaction is calculated from by summing the enthalpy changes of the intermediate steps that leads to the overall reaction.

Thus, the enthalpy change of the reaction:  A + 2B → C is determined as follows:

ΔH = ΔH₁ +  ΔH₂

In conclusion, the enthalpy change of the reaction is determined from the summation of the enthalpy changes that occur in the intermediate steps.

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Answer:

121 g/mol

Explanation:

To find the molar mass, you first need to calculate the number of moles. For this, you need to use the Ideal Gas Law. The equation looks like this:

PV = nRT

In this equation,

-----> P = pressure (atm)

-----> V = volume (L)

-----> n = moles

-----> R = constant (0.0821 L*atm/mol*K)

-----> T = temperature (K)

Because density is comparing the mass per 1 liter, I am assuming that the system has a volume of 1 L. Before you can plug the given values into the equation, you first need to convert Celsius to Kelvin.

P = 1.00 atm                         R = 0.0821 L*atm/mol*K

V = 1.00 L                             T = 25.0. °C + 273.15 = 298.15 K

n = ? moles

PV = nRT

(1.00 atm)(1.00L) = n(0.0821 L*atm/mol*K)(298.15 K)

1.00 = n(0.0821 L*atm/mol*K)(298.15 K)

1.00 = (24.478115)n

0.0409 = n

Now, we need to find the molar mass using the number of moles per liter (calculated) and the density.

0.0409 moles           ? grams           4.95 grams
----------------------  x  ------------------  =   ------------------
        1 L                       1 mole                     1 L

? g/mol = 121 g/mol

**note: I am not 100% confident on this answer

Answer:

2.30 moles MgCl₂

Explanation:

First, you need to balance the chemical equation. An equation is balanced when there is an equal amount of each element on both sides of the reaction. These values can be modified by adding coefficients in front of the molecules.

The unbalanced equation:

Mg (s) + HCl (aq) ---> MgCl₂ (s) + H₂ (g)

Reactants: 1 magnesium, 1 hydrogen, 1 chlorine

Products: 1 magnesium, 2 hydrogen, 2 chlorine

The balanced equation:

Mg (s) + 2 HCl (aq) ---> MgCl₂ (s) + H₂ (g)

Reactants: 1 magnesium, 2 hydrogen, 2 chlorine

Products: 1 magnesium, 2 hydrogen, 2 chlorine

Now, you need to use the mole-to-mole ratios from the balanced equation to convert between moles. Since we were not given a limiting reactant, the easiest way to find the actual moles of MgCl₂ is to start from both reactants.

4.59 moles Mg            1 mole MgCl₂
-------------------------  x  ------------------------  =  4.59 moles MgCl₂
                                       1 mole Mg

4.59 moles HCl           1 mole MgCl₂
-------------------------  x  ------------------------  =  2.30 moles MgCl₂
                                     2 moles HCl

Since HCl produces the smaller amount of product, it must be the limiting reactant. In other words, HCl runs out before all of the Mg is completely used up. Therefore, the actual amount of MgCl₂ produced in 2.30 moles.

1.506 × 10²³ molecules in  120.0 g of oxygen gas.

The slightest particle of importance contains all of the physical and chemical properties of that substance. Molecules are made up of one or more atoms.

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