What is Hess‘s law please help

Answer:

Concepts and reason

Lewis structure is a structure that explains the bonding between atoms of a molecule and lone pair of electrons that is present in the molecule is called a Lewis structure.

With the help  of Lewis structure the electronic geometry of a molecule can be determine.

Fundamentals

According to Lewis structure, every atom and their position in the structure of a molecule by using its chemical symbol.

Lines connecting the atoms that are bonded to them are drawn. Lone pairs are expressed by pairs of dots and are located beside the atoms.

Lewis structure  of [tex]H_{2}O[/tex] is, the total number of valence electrons is eight in [tex]H_{2}O[/tex].

Answer:

A. The law of definite proportions states that all pure samples of a particular chemical compound contain the same elements combines in the same proportion by mass.

B. The law of conservation of mass states that during ordinary chemical reactions, matter can neither be created or destroyed.

Note: The full question is as follows;

A researcher placed 25.0 g of silver chloride, AgCl, in sunlight and allowed the substance to decompose completely to form silver, Ag, with the release of chlorine gas, Cl2. The gas was collected in a container during the decomposition. The researcher determined that the mass of the silver formed was 18.8 g, and the mass of the chlorine gas formed was 6.2 g. The equation for the reaction is:

2AgCl ----> 2Ag + Cl2

a. State the law of definite proportions. Then use the researcher's data to confirm the law of definite proportions. Show your calculations.

b. State the law of conservation of matter. Then use the researcher's data to confirm the conservation of matter. Show your calculations.

Explanation:

A. Mass of silver obtained from AgCl = 18.8g.

Percentage mass of silver in the chloride = (18.8/25.0) * 100 = 75.2 %

Mass of chlorine obtained from AgCl = 6.2

Percentage mass of chlorine = (6.2/25) * 100 = 24.8 %

In one mole of AgCl with a molar mass of 143.3 g/mol; mass of silver = 107.8, mass of Cl = 35.5

Percentage mass of Ag = (107.8/143.3) * 100 = 75.2%

Percentage mass of Cl = (35.5/143.3) * 100 = 24.8%

Since the percentages by mass of Ag and AgCl obtained from the sample is the same to that obtained from a mole of AgCl, the law of definite proportions which states that all pure samples of a particular chemical compound contain the same elements combined in the same proportion by mass is verified.

B. Mass of reactant; AgCl sample = 25.0

Mass of products; At = 18.8 g; Cl = 6.2 g

Sum of products masses = 18.8 + 6.2 = 25.0 g

Therefore mass of reactant = mass of products.

This is in accordance with the law of conservation of mass which states that during ordinary chemical reactions, matter is neither created nor destroyed.

Answer:

2 - Butyne

Explanation:

The name of the molecule with a carbon atoms arranged in a straight chain with a triple bond between the second and third carbons is 2 - Butyne.

2- Butyne is an alkyne with structural formula given below. Some of the properties of Butyne include it is a produced artificially, it is volatile and colorless in nature.

Hence, the given molecules described is 2 - Butyne.

Answer:

A. Solubility of calcium sulfite increases

B. Solubility of calcium fluoride increases

C. Solubility of Silver bromide decreases

Explanation:

The solubility factor is proportional to ions' concentration. The solubility of a solution can be predicted from Le Chatelier's principle which states that if an external constraint is imposed on a system in equilibrium, the equilibrium position will shift in order to annul the effect of the external constraint. So, If the reactant's concentration increases, the equilibrium shifts to the right indicating a higher solubility of the solution and if the product's concentration increases, the equilibrium shifts to the left indicating a lesser solubility of the solution.

Case 1. Calcium sulfite

The dissociation reaction of CaSO3 is given below:

CaSO3 ----> Ca²+ + SO3²-

SO3²- is the conjugate base of the weak acid, H2SO3. Therefore, on the addition of hydrobromic acid, some of the sulfite ion is removed from the solution by the following reaction;

H+ + SO3²- ---> HSO3-

This shifts the equilibrium to the right, more dissociation, thereby resulting in more solubility of the solute.

Case 2. Calcium fluoride

The dissociation reaction of calcium fluoride (CaF2) is shown below.

CaF2 ----> Ca²+ + 2F-

Fluoride ion (F-) is a strong conjugate base of the weak acid. Therefore, some of fluoride ions is removed by the addition of hydrobromic acid as shown below:

H+ + F- ---->. HF

Hence, the concentration of fluoride ions reduces, shifting equilibrium in the forward direction. Therefore, the solubility will be more than in pure water solution.

Case 3: Silver bromide

The dissociation reaction of AgBr is as follows:

AgBr ----> Ag+ + Br-

The addition of HBr will increase the concentration of bromide ions. Hence, equilibrium will shift in backward direction resulting in a lesser solubility than in water.

The solubility of calcium sulfite and calcium fluoride is greater in 0.10 M hydrobromic acid solution than in pure water while the solubility of silver bromide is lesser in 0.10 M hydrobromic acid solution than in pure water.

Common ion effect refers to the decrease in solubility of a substance in a solution that contains another solute with which it has a common ion. If a substance is dissolved in a solution that contains a solute with which it has a common ion, the solubility of the substance in that solution is less than its solubility in pure water.

Considering the substances given, the solubility of calcium sulfite and calcium fluoride in 0.10 M hydrobromic acid solution is more than their solubility in pure water the equilibrium position is shifted in the forward direction.

However, solubility of silver bromide in 0.10 M hydrobromic acid solution is less than its solubility in pure water due to common ion effect.

Learn more: https://brainly.com/question/6505878

Answer:

The correct answer is 179.94 g/mol.

Explanation:

Based on the given question, the boiling point of diethyl ether us 34.500 degree C at 1 atm pressure. The boiling point of the solution given is 35.100 degree C. The Kb of diethyl ether given is 2.02 degree C/m. The weight of the compound given is 14.94 grams, the weight of the solvent (diethyl ether) is 279.5 grams.

The molecular weight of the compound can be determined by using the formula,

deltaTb = Kb * molality

Tb-To = Kb * molality

Tb-To = Kb*wt/mol.wt*1000/w (solvent)

35.100 - 34.500 = 2.02 * 14.94 / mol. wt * 1000 g / 279.5 g

0.6 = 2.02 * 53.45/ mol.wt

mol. wt = 2.02*53.45/0.6

mol. wt = 179.94 g/mol

Hence, the molecular weight of the compound is 179.94 gram per mol.

Answer:

 4.90  moles of  [tex]Mg(ClO_4)_2[/tex]   will produce  (9.8) moles of  [tex]Cl^{-}[/tex] ,

                                                    (4.90) moles of [tex]Mg^{2+}[/tex] and

                                                    (39.2) moles of  [tex]O^{2-}[/tex]

Explanation:

From the question we are told that

  The number of moles of  is  [tex]n = 4.90 \ mols[/tex]

The formation reaction of [tex]Mg(ClO_4)_2[/tex]  is

             [tex]Mg^{2+} + 2 Cl^{-} + 8O^{2+} \to Mg(ClO_4)_2[/tex]  

From the reaction we see that

   1 mole of  [tex]Mg(ClO_4)_2[/tex]  is formed by 2 moles of [tex]Cl^{-}[/tex] 1 mole of  [tex]Mg^{2+}[/tex] and 4  [tex]O^{2-}[/tex]

 This implies that

   4.90  moles of  [tex]Mg(ClO_4)_2[/tex]   will produce  (2 * 4.90) moles of  [tex]Cl^{-}[/tex] ,

                                                    (1 * 4.90) moles of [tex]Mg^{2+}[/tex] and

                                                    (8 * 4.90) moles of  [tex]O^{2-}[/tex]

So

  4.90  moles of  [tex]Mg(ClO_4)_2[/tex]   will produce  (9.8) moles of  [tex]Cl^{-}[/tex] ,

                                                    (4.90) moles of [tex]Mg^{2+}[/tex] and

                                                    (39.2) moles of  [tex]O^{2-}[/tex]

Answer:

- [tex]n_{Mg}=4.90molMg[/tex]

- [tex]n_{Cl}=9.6molCl[/tex]

- [tex]n_{O}=38.4molO[/tex]

Explanation:

Hello,

In this case, for the given 4.90 moles of magnesium perchlorate, we can compute the moles of each atom by identifying the subscript each atom has in the molecule as shown below:

- Moles of magnesium atoms: here, one mole of magnesium perchlorate has only one mole of magnesium atom (subscript is one), this the moles of magnesium atoms are also 4.90 moles.

- Moles of chlorine atoms: here, one mole of magnesium perchlorate has two moles of chlorine atoms as it has a two out of the parenthesis enclosing the perchlorate anion, thus, we have:

[tex]n_{Cl}=4.80molMg(ClO_4)_2*\frac{2molCl}{1molMg(ClO_4)_2} =9.6molCl[/tex]

- Moles of oxygen atoms: here, one mole of magnesium perchlorate has eight moles of oxygen atoms as it has a four in the oxygen subscript and a two out of the parenthesis enclosing the perchlorate anion, thus, we have:

[tex]n_{O}=4.80molMg(ClO_4)_2*\frac{8molO}{1molMg(ClO_4)_2} =38.4molO[/tex]

Best regards.

Answer:

C = 98%

Explanation:

Hello,

To determine the percentage of salt recovered, we'll divide the mass of the salt recovered over by the original mass of the salt.

Mass of salt recovered = 1.47g

Initial mass of salt = 1.50g

Percentage of salt recovered = (mass recovered/ initial mass of salt) × 100

Percentage of salt recovered = (1.47 / 1.50) × 100

Percentage of salt recovered = 0.98 × 100

Percentage of salt recovered = 98%

The percentage of salt recovered is equal to 98%

Answer:

CH4 (g) + O2 (g) → CO2 (g) + H2O (g)

This is a combustion reaction.

Explanation:

The combination of methane (CH4) and oxygen (O2) yields carbon dioxide (CO2) and water (H2O).

CO2 is typically a gas, and water, in this case, is in a gas form because it evaporated.

The reaction is combustion because the methane reacts with the oxygen to produce carbon dioxide and water. Combustion reactions must involve O2 as one reactant.

Answer:

[tex]Q=450.14J[/tex]

Explanation:

Hello,

In this case, for the given equation to compute the heat, we should compute the mass of the solution of hydrochloric acid, thus, the first step is to compute its reacting mass:

[tex]m_{HCl}^{reacting}=2\frac{mol}{L}*0.1000L *\frac{36.45g}{1mol}=7.29g[/tex]

Then, we obtain the total mass of the formed solution:

[tex]m=0.25g+7.29g=7.54g[/tex]

In such a way, we can infer that the specific heat of the solution is mainly the specific heat of hydrochloric acid, therefore the heat turns out:

[tex]Q=3.98\frac{J}{g\°C} *7.54g*(35.0\°C-20.0\°C)\\\\Q=450.14J[/tex]

Regards.

Answer: brainliesss plssssssss

0.256 L  

Explanation:

We should use the following formula:

concentration (1) × volume (1) =  concentration (2) × volume (2)

concentration (1) = 0.82 M NaOCl

volume (1) = ?

concentration (2) = 0.21 M NaOCl

volume (2) = 1 L

volume (1) = [concentration (2) × volume (2)] / concentration (1)

volume (1) = [0.21 / 1] / 0.82 = 0.256 L

Complete Question

The complete question is shown on the first uploaded image

Answer:

Part A

    activation barrier for the reaction [tex]E_a = 84 .0 \ KJ/mol[/tex]

Part B

    The frequency plot is  [tex]A = 2.4*10^{13} s^{-1}[/tex]    

Explanation:

From the question we are told that

     at  [tex]T_1 = 300 \ K[/tex]   [tex]k_1 = 5.70 *10^{-2}[/tex]

and  at  [tex]T_2 = 310 \ K[/tex]   [tex]k_2 = 0.169[/tex]

The  Arrhenius plot is mathematically represented as

      [tex]ln [\frac{k_2}{k_1} ] = \frac{E_a}{R} [\frac{1}{T_1} - \frac{1}{T_2} ][/tex]

Where [tex]E_a[/tex] is the activation barrier for the reaction

         R is the gas constant with a value of  [tex]R = 8.314*10^{-3} KJ/mol \cdot K[/tex]

Substituting values

          [tex]ln [\frac{0.169}{6*10^-2{}} ] = \frac{E_a}{8.314*10^{-3}} [\frac{1}{300} - \frac{1}{310} ][/tex]

=>       [tex]E_a = 84 .0 \ KJ/mol[/tex]

The  Arrhenius plot can also be  mathematically represented as

      [tex]k = A * e^{-\frac{E_a}{RT} }[/tex]

Here we can use any value of k from the data table with there corresponding temperature let take  [tex]k_2 \ and \ T_2[/tex]

So substituting values

        [tex]0.169 = A e ^{- \frac{84.0}{8.314*10^{-3} * 310} }[/tex]

=>       [tex]A = 2.4*10^{13} s^{-1}[/tex]    

Explanation:

it is used to describe those action of adrenal corticosteroids that produce sodium

Answer:

[tex]\Delta H=-11897J[/tex]

Explanation:

Hello,

In this case, it is widely known that for isochoric processes, the change in the enthalpy is computed by:

[tex]\Delta H=\Delta U+V\Delta P[/tex]

Whereas the change in the internal energy is computed by:

[tex]\Delta U=nCv\Delta T[/tex]

So we compute the initial and final temperatures for one mole of the ideal gas:

[tex]T_1= \frac{P_1V}{nR}=\frac{10.90atm*4.86L}{0.082*n}=\frac{646.02K }{n} \\\\T_2= \frac{P_2V}{nR}=\frac{1.24atm*4.86L}{0.082*n}=\frac{73.49K }{n}[/tex]

Next, the change in the internal energy, since the volume-constant specific heat could be assumed as ³/₂R:

[tex]\Delta U=1mol*\frac{3}{2} (8.314\frac{J}{mol*K} )*(73.49K-646.02K )=-7140J[/tex]

Then, the volume-pressure product in Joules:

[tex]V\Delta P=4.86L*\frac{1m^3}{1000L} *(1.24atm-10.90atm)*\frac{101325Pa}{1atm} \\\\V\Delta P=-4756.96J[/tex]

Finally, the change in the enthalpy for the process:

[tex]\Delta H=-7140J-4757J\\\\\Delta H=-11897J[/tex]

Best regards.

The change in enthalpy is 70.42J

Data;

The change of enthalpy is calculated as

[tex]\delta H = \delta V + \delta nRT\\\delta n = 0\\\delta H = \delta U \\[/tex]

The volume change is negligible

The change in enthalpy here is equal to change in internal energy over ΔE

[tex]\delta H = \delta U = nCv\delta T\\\delta H = \frac{3}{2}(nR\delta T)\\\delta H = \frac{3}{2}\{\delta PV)\\ \delta H = \frac{3}{2}[(10.90-1.24)*4.86] \\\delta H = 70.42J[/tex]

The change in enthalpy is 70.42J

Learn more on change in enthalpy here;

https://brainly.com/question/14047927

Answer:

ΔErxn[tex]= -3.90*10^3KJ[/tex]

Explanation:

Given from the question

T1 = 25.87∘C

T2= 38.13∘C.

C= 5.73Kj/C

CHECK THE ATTACHMENT FOR DETAILED EXPLATION

Explanation:

P(aq)+Q(aq)⇌3R(aq)

This problem involves applying LeChatelier's principle.

LeChatelier's principle states that whenever a system in equilibrium is disturbed, the equilibrium position would change in order to annul that change.

1) Increase [P]

This would cause the equilibrium position to shift to the right. This is because more reactions have been added, to annul that change more products have to be formed.

2) Increase [Q]

This would cause the equilibrium position to shift to the right. This is because more reactions have been added, to annul that change more products have to be formed.

3) Increase [R]

This would cause the equlibrium position to shift to the left. This is because more products have been formed, to annul that change more reactants have to be formed.

4) Decrease [P]

This would cause the equlibrium position to shift to the left. This is because there are now less reactants, to annul that change more reactants have to be formed.

5) Decrease [Q]

This would cause the equilibrium position to shift to the left. This is because there are now less reactants, to annul that change more reactants have to be formed.

6) Decrease [R]

This would cause the equilibrium position to shift to the right. This is because there are now less products, to annul that change more products have to be formed.

7) Triple [P] and reduce [Q] to one third

No shift in the direction of the net reaction because both changes cancels each other.

8) Triple both [Q] and [R]

No shift in the direction of the net reaction because both changes cancels each other.

Answer: D. They would device an experiment that could test the two scientists conclusions.

Explanation:

The results of the scientific study must be verified by peer scientists or members of the scientific community to proof whether the research has been conducted produce a valid evidence.

In the given situation, the two scientists had developed different conclusion for the same experiment. This may mean either of the two may have put up an incorrect conclusion.

The scientific community may address this issue by performing the experiment. Every scientific conclusion is based upon the results of the experimental approach.

Answer:d

Explanation:

Answer:

1.63 V

Explanation:

Let us state the reaction equation again for the purpose of clarity;

2MnO4^-(aq)+16H+(aq)+5Pb(s)-->2Mn^2+(aq)+8H2O(l)+5Pb^2+(aq)

The reduction potentials for the two half reaction equations are;

MnO 4 - (aq) + 8H + (aq) + 5e - → Mn2+(aq) + 4H2O(l) Eo=1.51 V

Pb2+(aq) + 2e - → Pb(s) Eo= -0.13 V

E°cell = E°red – E°Ox

E°cell = 1.51 - (-0.13)

E°cell = 1.51 + 0.13

E°cell = 1.64 V

But Q= [Mn^2+]^2 [Pb^2+]^5/[MnO4^-]^2 [H^+]^16

Q= [3.23]^2 [6.62]^5/[1.87]^2 [1.37]^16

Q= 10.43 × 12714.22/3.4969 × 154

Q= 132609.3/538.5226

Q= 246.25

From Nernst equation

E= E° - 0.0592/n log Q

Where n=10

E= 1.64- 0.0592/10 log 246.25

E= 1.64-0.0142

E= 1.63 V

Answer:

Homo nuclear molecule mean having atoms of only one element,

I cant see clearly the option B and C can you correct them , 2002? Hz?

Explanation:

Answer:

H2

Explanation:

Answer:

(D) K = 4.5 x 10⁵. The reaction favors the formation of products

Explanation:

HCOOH + CN⁻ ⇆ HCOO⁻ + HCN

K = [HCOO⁻] [ HCN ] / [ HCOOH] [ CN⁻]

HCOOH ⇄ H ⁺ + COO⁻

K₁ = [ H⁺] [ COO⁻ ] / [HCOOH ]

HCN ⇆ H⁺ + CN⁻

K₂ = [ H⁺] [ CN⁻] / [ HCN ]

K₁ / K₂

= [ H⁺] [ COO⁻ ] / [HCOOH ]  X  [ HCN ] / [ H⁺] [ CN⁻]

= [ COO⁻ ][ HCN ] / [HCOOH ]  [ CN⁻]

= K

K = K₁ / K₂

= 1.8  x 10⁻⁴ / 4 x 10⁻¹⁰

= 4.5 x 10⁵

So equilibrium constant of the reaction

HCOOH + CN⁻ ⇆ HCOO⁻ + HCN

is very high . Hence reaction favours the formation of product.

option (D) is correct.

Answer:

18130 mm

Explanation:

Now we have a lot of unit conversions to do in order to correctly answer this question. We shall do these conversions gradually.

First we convert the weight in ounce to grams.

If 1 ounce = 28.4g

12 ounces = 12×28.4 = 340.8 g

Next we convert the area of aluminum from ft2 to m2

1ft2= 0.0929 m2

75 ft2= 75 × 0.0929= 6.9675m2

Now density of aluminum= 2.70 gcm-3

Density= mass/volume

But volume= area× thickness

Density= mass/ area × thickness

Density × area × thickness= mass

Thickness= mass/ density × area

Thickness= 340.8g / 2.70gcm-3 × 6.9675m2

Thickness= 340.8/18.8

Thickness= 18.13 m

Since 1000 milimeters make 1 metre

Thickness= 18130 mm

Answer:

Hypothesis is an assumption or idea about a particular topic or argument. An hypothesis should be one which is able to be tested and measurable to determine its authenticity.

A theory is an explanation of a scientific observation which has undergone series of experiments and is reproducible in any part of the world.

A law is simply a rule which gives an in depth explanation of a scientific finding. If new findings emerge the law could be changed or modified.

Answer: The oxygen's oxidation number is -2.

Explanation:

For formation of a neutral ionic compound, the charges on cation and anion must be balanced. The cation is formed by loss of electrons by metals and anions are formed by gain of electrons by non metals.

In [tex]Fe_2O_3[/tex], Fe is having an oxidation state of +3 called as  cation and oxygen  is an anion with oxidation state of -2. Thus they combine and their oxidation states are exchanged and written in simplest whole number ratios to give neutral [tex]Fe_2O_3[/tex]

The cations and anions being oppositely charged attract each other through strong coloumbic forces and form an ionic bond.

Answer:

Answer is letter B

Explanation:

The first one is wrong because acids release H+, not bases.

The third one is wrong because the pH is exactly 7, not greater.

The last one is wrong because it is vague and does not fit a neutralization reaction.

Answer:

U = -45.557kj

Explanation:

Before we can calculate the totally internal energy change in kilojoules firstly we need to calculate W

U=q + w .

We know that

w = PΔ V

where P is the pressure of

and V is the volume

then we can calculate the work

w = 35 atm * ( 8.20L - 2.21L)

W=35atm* 5.99L

W=209.65atmJ

But 1 atm = 101.325J

then ,

w = 209.65* 101.325 J = 21242.79 J

let us convert it to Kj

But we know that 1kJ = 10^3 J .

Then w = 21.243 kJ .

Then we can now calculate the internal energy as

U = 21.243- 66.8 kJ = -45.557kj

But we know that heat was released. Theeefore, the total internal energy change was -45.557kj

Answer:

0.263M of CH₃COOH is the concentration of the solution.

Explanation:

The reaction of acetic acid (CH₃COOH) with NaOH is:

CH₃COOH + NaOH → CH₃COO⁻Na⁺ + H₂O

1 mole of acetic acid reacts per mole of NaOH to produce sodium acetate and water.

In the equivalence point, moles of acetic acid are equal to moles of NaOH and moles of NaOH are:

0.0375L × (0.175 moles / L) = 6.56x10⁻³ moles of NaOH = moles of CH₃COOH.

As the sample of acetic acid had a volume of 25.0mL = 0.025L:

6.56x10⁻³ moles of CH₃COOH / 0.0250L =

0.263M of CH₃COOH is the concentration of the solution

Answer:

Explanation:

The larger sediment particles are having more weright(mass), hence fall quickly (early) and smaller particles with low mass are carried by wind for longer time and falls slowly ,  hence you observe sorted kind of things. Hope this helps you to understadn this phenomenon.

Answer:

43.964

Explanation:

i think i used a calculator so let me know if its wrong

Answer:

39.49 kg

Explanation:

:)

Answer:

C. Na₂SO₄(aq) + Sr(NO₃)₂(aq) → SrSO₄(s) + 2 NaNO₃(aq)

Explanation:

Based on the equation:

Na₂SO₄(aq) + Sr(NO₃)₂(aq) → SrSO₄(s) + NaNO₃(aq)

As you can see, sulfate ions (SO₄) are been replaced for nitrate ions (NO₃). That is a double replacement reaction and is a very important information because 2 NO₃ ions in Sr(NO₃)₂ are producing 1 NO₃ ion. To balance NO₃:

Na₂SO₄(aq) + Sr(NO₃)₂(aq) → SrSO₄(s) + 2 NaNO₃(aq)

1 SO₄ ion in Na₂SO₄ produce 1 SO₄ ion in SrSO₄. And Na and Sr metals are balanced yet. Thus, the balanced form of this chemical equation is: