Answer:
ΔH°rxn = -827.5 kJ
Explanation:
Let's consider the following balanced equation.
2 PbS(s) + 3 O₂(g) → 2 PbO(s) + 2 SO₂(g)
We can calculate the standard enthalpy of reaction (ΔH°rxn) from the standard enthalpies of formation (ΔH°f) using the following expression.
ΔH°rxn = [2 mol × ΔH°f(PbO(s)) + 2 mol × ΔH°f(SO₂(g) )] - [2 mol × ΔH°f(PbS(s)) + 3 mol × ΔH°f(O₂(g) )]
ΔH°rxn = [2 mol × ΔH°f(PbO(s)) + 2 mol × ΔH°f(SO₂(g) )] - [2 mol × ΔH°f(PbS(s)) + 3 mol × ΔH°f(O₂(g) )]
ΔH°rxn = [2 mol × (-217.32 kJ/mol) + 2 mol × (-296.83)] - [2 mol × (-100.4) + 3 mol × 0 kJ/mol]
ΔH°rxn = -827.5 kJ
The standard enthalpy of the reaction is -827.5 kJ/mol
The standard enthalpy of reaction [tex]\mathbf{\Delta H^0_{rxn}}[/tex] is the enthalpy change that happens in a system whenever one mole of the matter is converted through a chemical process under normal conditions.
The given reaction can be expressed as:
2PbS(s) + 3O₂(g) → 2PbO(s) + 2SO₂(g)
The standard enthalpy can be represented by the equation:
[tex]\mathbf{\Delta H^0_{rxn} = \sum \Delta _f ^0(products) - \sum \Delta _f^0(reactants)}[/tex]
At standard conditions, the standard enthalpies of formation of the given species are:
ΔH°f(PbO(s)) = 219 kJ/molΔH°f(SO₂(g)) = -296.83 kJ/molΔH°f(PbS(s)) = 100.4 kJ/molΔH°f(O₂(g)) = 0 kJ/mol
∴
[tex]\mathbf{ \Delta H^0_{rxn} = \Big[2 mol \times \Delta H^0_f(PbO(s)) + 2 mol \times \Delta H^0_ f(SO_2(g) )\Big] - \Big[2 mol \times \Delta H^0_f (PbS(s))} + \mathbf{ 3 mol \times \Delta H^0_f(O_2(g) )\Big] }}[/tex]
[tex]\mathbf{\Delta H^0rxn = [2 mol \times (-217.32 kJ/mol) + 2 mol \times (-296.83)] - [2 mol \times (-100.4)} \\ \mathbf{+ 3 mol \times 0 kJ/mol]}}[/tex]
[tex]\mathbf{\Delta H^0rxn = -827.5 \ kJ/mol}}[/tex]
Therefore, we can conclude that the standard enthalpy of the reaction is -827.5 kJ/mol
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Which condition produces an anion?
A. more neutrons than electrons
B. more protons than electrons
C. more electrons than neutrons
D. more electrons than protons
The solubility of limestone, CaCO3, at 25˚C is 0.00067 g/100 mL. Write the chemical equation for the solubility equilibrium of this sparingly soluble salt in water. Then compute the molar solubility and the solubility product constant Ksp for CaCO3 at 25˚C.
Answer:
4.5 × 10⁻⁹
Explanation:
Step 1: Write the reaction for the solution of CaCO₃
CaCO₃(s) ⇄ Ca²⁺(aq) + CO₃²⁻(aq)
Step 2: Convert the solubility of CaCO₃ from g/L to mol/L
We will use the following conversion factors:
The molar mass of CaCO₃ is 100.09 g/mol.1 L= 1000 mL.There are 0.00067 g of CaCO₃ per 100 mL of solution.[tex]\frac{0.00067 gCaCO_3}{100mLSol} \times \frac{1molCaCO_3}{100.09gCaCO_3} \times \frac{1000mLSol}{1LSol} = 6.7 \times 10^{-5} M[/tex]
Step 3: Calculate the solubility product constant (Ksp)
To relate Ksp and the molar solubility (S), we need to make an ICE chart.
CaCO₃(s) ⇄ Ca²⁺(aq) + CO₃²⁻(aq)
I 0 0
C +S +S
E S S
The solubility product constant is:
Ksp = [Ca²⁺].[CO₃²⁻] = S² = (6.7 × 10⁻⁵)² = 4.5 × 10⁻⁹
What is the main function of the muscular system A. digestion B. breathing C.movement D. Eliminating
Answer:
C, Movement
Explanation:
The water bottle contains 575 grams of water at 80°C. The water eventually cools to
40°C. How many calories of heat could be transferred to the student's back?
Answer:
–23000 Calories.
NOTE : The negative sign indicates that heat has been loss to the student back.
Explanation:
The following data were obtained from the question:
Mass (M) of water = 575 g
Initial temperature (T1) = 80 °C
Final temperature (T2) = 40 °C
Heat (Q) transferred =.?
Next, we shall determine the change in temperature (ΔT).
This is illustrated below:
Initial temperature (T1) = 80 °C
Final temperature (T2) = 40 °C
Change in temperature (ΔT) =?
Change in temperature (ΔT) = T2 – T1
Change in temperature (ΔT) = 40 – 80
Change in temperature (ΔT) = –40°C
Finally, we shall determine the heat transferred. This can be obtained as follow:
Mass (M) of water = 575 g
Change in temperature (ΔT) = –40°C
Specific heat capacity (C) of water = 1 Cal/g°C
Heat (Q) transferred =.?
Q = MCΔT
Q = 575 × 1 × –40
Q = –23000 Calories
NOTE : The negative sign indicates that heat has been loss to the student back.
What is the momentum of a 1kg ball moving at 5m/s?
Answer:
5Ns
momentum= mass *velocity
=1*5
=5Ns
what is the hydronium ion concentration in a solution formed by combining 750mL of 0.10M NaOH with 250mL of 0.30 M HCl
Answer:
[tex][H^+]=1x10^{-7}M[/tex]
Explanation:
Hello.
In this case, since the reaction between sodium hydroxide and hydrochloric acid has a 1:1 mole ratio between them:
[tex]NaOH+HCl\rightarrow NaCl+H_2O[/tex]
In order to compute the hydronium H⁺ concentration in the mixed volumes of the given solutions we first compute the moles of each reactant:
[tex]n_{NaOH}=0.750L*0.10mol/L=0.075mol\\\\n_{HCl}=0.250L*0.30mol/L=0.075mol[/tex]
As seen, since those amounts are the same, we infer all the acid and base are consumed so the pH is 7 because a neutral salt is produced, and the corresponding H⁺ concentration is:
[tex][H^+]=10^{-pH}=10^{-7}=1x10^{-7}M[/tex]
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Sodium is located above potassium in Group 1 of the periodic table. If a potassium ion has a charge of +1, what is the charge on a sodium ion?
A. -1
B 0
C. +1
D +2
Answer:
C
Explanation:
It will be the same. That's what moving down a column means. The properties are going to be quite similar.
Which of the following best describes the structure of a carbohydrate?
a
Carbon ring(s)
b
Single or double helix
c
Hydrocarbon(s)
d
Globular or fibrous
Answer:
A
Explanation:
B- is dna related
C i dunno
and d is about protein so that leaves A
How many atoms of Carbon are found on the PRODUCTS side?
A. In a separatory funnel containing ethyl acetate and 10% aqueous sodium bicarbonate (NaHCO3), which layer would contain the brominated aromatic compound?
Answer:
ethyl acetate layer
Explanation:
This question tests your knowledge of the principle of solvent extraction.
In solvent extraction, there is always an organic layer and an aqueous layer. The ethyl acetate is the organic layer while the sodium bicarbonate is the aqueous layer.
A brominated aromatic compound will be extracted into the organic layer (ethyl acetate layer).
Which of the following is one way creativity can help scientists?
By ensuring they follow the scientific method
By increasing the amount of time it takes to complete scientific experiments
By making sure they only try things that have already been proven
By leading them to ask more questions about the natural world
Answer:
Creativity can help scientists by leading them to ask more questions about the natural world.
Explanation:
Beacause they use creativity to make up questions about the natural world.
what is the first step in the scientific inquiry process
Answer:
make an observation that describes a problem
Explanation:
Answer:
The first step in the Scientific Method is to make objective observations.
Explanation:
....-
20 POINTS PLEASE ANSWER ASAP!!!!
Why is calcium (Ca) in group 2, period 4 on the periodic table?
A Calcium, like all group 2 elements, is nonreactive and a gas at room temperature.
B Calcium, like all period 4 elements, is nonreactive and a gas at room temperature,
C Calcium, like all group 2 elements, is reactive and a solid at room temperature.
D. Calcium, like all period 4 elements, is reactive and a solid at room temperature.
Calcium (Ca) is in group 2 and period 4 on the periodic table be because Calcium has 2 valence electrons and 4 electron shell. Thus, calcium is a metal like all other group 2 element.
The correct answer to the question is Option C. Calcium, like all group 2 elements, is reactive and a solid at room temperature.
Calcium is a group 2 element majorly because it has 2 valence electrons. It is also in period 4 because it has 4 electron shells.
Being a group 2 element, calcium is a solid at room temperature and also reactive. All elements in the group 2 are metals.
There are other elements in period 4 which are not solid. For example krypton is an element in period 4 and it is a gas and not reactive.
From the above information, we can conclude that the correct answer to the question is:
Option C. Calcium, like all group 2 elements, is reactive and a solid at room temperature.
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You are given an unknown mixture containing NaCl and NaHCO3. When you carry out the heating exactly as described in part A, only NaHCO3 decomposes. From the loss in mass, you can calculate the amount of NaHCO3 present in the mixture and its mass percent composition.
Here is your data. Incorporate it in your written procedure.
Experimental data Unknown (NaCl + NaHCO3)
Mass of crucible + cover 72.428 g
Mass of crucible + cover + mixture 74.80 g
Mass of crucible + cover + residue (1st heating) 74.25 g
Mass of crucible + cover + residue (2nd heating) 74.24 g
Mass of crucible + cover + residue (3rd heating) 74.24
From the data above, carry out your calculation for finding the mass of mixture, and mass of final solid remaining in the crucible. Using the knowledge that only loss of mass due to CO2 and H2O can be linked to the original mass of NaHCO3, calculate the mass of NaHCO3 and percent of NaHCO3 in the mixture.
Answer:
1.52g NaHCO3 were in the original mixture.
Mass percent: 64.1%
Explanation:
When NaHCO3 heats it descomposition occurs as follows:
2 NaHCO3(s) → Na2CO3(s) + CO2(g) + H2O(g).
The loss in mass is because of the evaporization of CO2 and H2O. As both are in the same porportion, its molar mass is the sum of both compounds (44g/mol + 18g/mol = 62g/mol)
Loss in mass: 74.80g - 74.24g = 0.56g.
In moles:
0.56g * (1mol / 62g) = 0.00903 moles of gas.
As 1 mole of the gases comes from 2 moles of NaHCO3:
Moles NaHCO3:
0.00903 moles of gas * (2 moles NaHCO3 / 1 mole gas) = 0.018 moles NaHCO3.
In grams (Molar mass NaHCO3: 84g/mol):
0.018 moles NaHCO3 * (84g / mol) = 1.52g NaHCO3 were in the original mixture.
The mass of the mixture was:
74.80g - 72.428g = 2.372g
That means mass percent of NaHCO3 is:
(1.52g / 2.372g) * 100 = 64.1%
BaCl2+Na3PO4-->NaCl+Ba3 (PO4)2If 3.54g of Ba3 (PO4)2are produce by the reaction given how many grams of the starting material BCl2 were used?a) 3.680 gb) 1.23 gc) 3.68 gd) 4.16 g
Answer:
1.23 g
Explanation:
Given that the mass of barium phosphate formed= 3.54 g
Molar mass of Ba3 (PO4)2 = 602 g/moles
Number of moles of Ba3 (PO4)2= 3.54g/602 g/moles = 0.0059 moles
Since 1 mole of BaCl2 forms 1 mole of Ba3 (PO4)2
Hence, 0.0059 moles of BaCl2 yields 0.0059 moles of Ba3 (PO4)2
Hence mass of BaCl2 reacted= mass × molar mass= 1.23 g
3. A certain Chemical Industry company has a quality control job opening. The job is open for any major with basic knowledge of chemistry. You decided to apply. In the interview the HR personnel gives you a sealed folder from a certain lot to test your laboratory experience, as well as your quantitative and volumetric analysis skills. The chemical contained in the sample is benzoic acid (C-H602) and it is known to be a monoprotic acid. In order to get the job, you need to determine if the sample's purity is acceptable based on their standards. Inside the folder you found a vial with a solid sample labeled BA-I, a periodic table, and the following data: 1.250 g of the sample required 20.15 mL of 0.500 M concentration of NaOH to reach the end point. The lot can be denied if the purity is below 99.5 % purity.
1) What is the purity in the sample?
2) Is it the purity acceptable?
3) Would you repeat the titration experiment?
Answer:
1) 97.6%
2) No the purity is not acceptable because the standard is 99.5% purity.
3) Yes I will repeat the titration experiment to confirm my result.
Explanation:
Equation of the reaction;
C7H6O2(aq) + NaOH(aq) ---------> C7H5ONa(aq) + H2O(aq)
From the information provided;
Number of moles of NaOH reacted = concentration × volume = 20.15/1000 × 0.500 = 0.01 moles
From the reaction equation;
1 mole of C7H6O2 reacts with 1 mole of NaOH
Hence 0.01 moles of C7H6O2 will react with 0.01 moles of NaOH
Mass of C7H6O2 reacted = number of moles of C7H6O2 × molar mass of C7H6O2
Molar mass of C7H6O2 = 122.12 g/mol
Mass of C7H6O2 reacted = 0.01 moles × 122.12 g/mol = 1.22 g
Percentage by mass of pure C7H6O2 in the impure sample = 1.22/1.250 × 100 = 97.6 %
What is the mass in grams of 2.5 moles of Al?
Answer:
One mole of Al weighs 27g.
2.5 moles of Al weigh 67.5g.
Which of the following is an example of a chemical change that occurs in your home?
A) Water boiling on the stove
B) Composting your own fertilizer
C) Smashing a window with a baseball
D) Adding food coloring to icing for a cake
Which are characteristics of all living things?
Order, sensitivity or response to the environment, reproduction, growth and development, regulation, homeostasis, and energy processing.
Neon effuses 1.26 times as fast an an unknown gas at a particular temperature. What is the molar mass of the unknown gas
Answer:
31.75 amu
Explanation:
Using Graham's equation of effusion as depicted below:
V1/V2 = √m2/√m1
Where; v1 = speed of neon gas
V2 = speed of unknown gas
m1 = molar mass of neon gas
m2 = molar mass of unknown gas
According to this question: v1 = 1.26x, m1 = 20amu, v2 = 1x, m2 = ?
Hence,
1.26x/1x = √m2/√20
1.26/1 = √m2/4.472
√m2 = 4.472 × 1.26
√m2 = 5.635
m2 = 5.635²
m2 = 31.75 amu
Therefore, the molar mass of the unknown gas is 31.75 amu.
Assume that silver and gold form ideal, random mixtures. Calculate the mass of pure Ag needed to cause an entropy increase of 20 J/K when mixed with 100g of pure Au
Answer:
[tex]m_{Ag}=2,265.9g[/tex]
Explanation:
Hello!
In this case, since the definition of entropy in a random mixture is:
[tex]\Delta S=-n_TR\Sigma[x_i*ln(x_i)][/tex]
For this silver-gold mixture we write:
[tex]\Delta S=-(n_{Au}+n_{Ag})R\Sigma[\frac{n_{Au}}{n_{Au}+n_{Ag}} *ln(\frac{n_{Au}}{n_{Au}+n_{Ag}} )+\frac{n_{Ag}}{n_{Au}+n_{Ag}} *ln(\frac{n_{Ag}}{n_{Au}+n_{Ag}} )][/tex]
By knowing the moles of gold:
[tex]n_{Au}=100g*\frac{1mol}{197g} =0.508mol[/tex]
It is possible to write the aforementioned formula in terms of the variable [tex]x[/tex] representing the moles of silver:
[tex]20\frac{J}{mol}=-(0.508+x)8.314\frac{J}{mol*K} \Sigma[\frac{0.508}{0.508+x} *ln(\frac{0.508}{0.508+x} )+\frac{x}{0.508+x} *ln(\frac{x}{0.508+x} )][/tex]
Which can be solved via Newton-Raphson or a solver software, in this case, I will provide you the answer:
[tex]x=n_{Ag}=21.0molAg[/tex]
So the mass is:
[tex]m_{Ag}=21.0mol*\frac{107.9g}{1mol}\\ \\m_{Ag}=2,265.9g[/tex]
Best regards!
What are the similarities between the adrenal hormone cortisone and the synthetic corticoid prednisone?
a. Both have a steroid nucleus
b. Both have 3 ketone groups
c. Both have 2 methyl
d. Both have 2 hydroxy group
e. Both have the same number of double bonds.
Answer:
Options a,b, c and d are correct
Explanation:
From the diagram attached in the picture below, They both have steroid nucleus since they have functional groups (such as the methyl and the ketone groups) that are spatially attached. It can also be deduced that both structures have three (3) ketone groups (CO/C=O), two (2) methyl groups (CH₃) and two (2) hydroxyl groups (OH). Hence, options a, b,c and d are correct.
However, cortisone has one (1) double bond while prednisone has two (2) double bonds.
the mass number of Fe is 56 . how many neutron are there in a single Fe atom
Answer:
30 neutrons
Explanation:
Since the mass of the iron nuclide is 56 , there must be 56−26=30 neutrons, 30 massive, neutral particles in this iron nucleus.
The three dots in the Lewis dot diagram for boron indicates that it. Please help
Answer:
valence electrons
Explanation:
it is outermost shell of electrons
The three dots in the Lewis dot diagram for boron indicates that it has three valence electrons.
The three dots in the Lewis dot diagram for boron indicates that it
can bond with three other atoms. NO. It can bond with less than 3 atoms by forming double or triple bonds.can only form triple covalent bonds. NO. It can also form single and double covalent bonds.has three valence electrons. YES. It has 3 electrons in the outermost electron shell.scores a 3 on Pauling's electronegativity scale. NO. The electronegativity of boron is 2.04.The three dots in the Lewis dot diagram for boron indicates that it has three valence electrons.
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A group of students are studying the movement of thermal energy. The teacher asks the students to place the palms of their hands flat on their tabletops and describe what is happening. Which statement below best describes why the table feels cold?
Answer:
The table feels cold because it is at a lower temperature than the students' hands, and thermal energy is being pulled into the table.
Explanation:
The thermal conductivity of the table is low and so it feels cold.
What is Thermal Conductivity?Thermal conductivity is the measure of the ability of a material to conduct heat.
The rate at which heat is transported by conduction through a material's unit cross-section area when a temperature gradient exits perpendicular to the area is known as thermal conductivity.
Thermal energy is the energy contained within a system that accounts for the temperature of the system.
The human body cannot measure the temperature of any object but it can feel the difference in the temperature.
If one body is at 20 degrees Celsius, and an object is at 30 degrees Celsius, then the body will feel hot when the object is touched.
Similarly, when the students touched the table, the conductivity of the wood is very low, and it feels cold.
The thermal energy of the table is lower than the thermal energy of the body.
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the two stages of cellular respiration.
Which belongs in the area marked X?
Energy is released.
Oxygen is used up.
Glucose is broken down.
Carbon dioxide is used up.
Answer:
Oxygen is used up
Explanation:
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A 100.00-mL water sample was adjusted to pH 10 and titrated to the calmagite endpoint with 10.87 mL of 0.0125 M EDTA solution. Then the pH of another 100.00-mL water sample was adjusted to pH 12 and titrated with EDTA to the calcon endpoint. In this second titration, 2.63 mL of titrant was required. Calculate the concentration of Mg2 and Ca2 in the water. Express your answers in mg/L of CaCO3 and MgCO3, respectively.
Answer:
The mass of Ca²⁺ present in the water sample = 13.23 mg/L.
The mass for the Mg²⁺ in the water sample = 25.06 mg/L.
Explanation:
We are given the following set of values which are going to aid in solving this particular question/problem. Thus, the parameters or data or information is given below:
First part:
Total volume of the water sample = 100.00-mL water sample, volume of the EDTA solution = 10.87 mL, the concentration of the EDTA solution = 0.0125 M, the adjusted pH of the water sample with = 10.
Second part:
Total volume of the water sample = 100.00-mL water sample, volume of the EDTA solution = 2.63 mL and the adjusted pH of the water sample with = 12.
Thus, the first thing to do now is to determine the number of moles of the EDTA solution in Ca²⁺ titration which is; 0.0125 x 0.00263 = 3.30 x 10⁻⁵ moles.
The mass of Ca²⁺ present in the water sample = [3.30 x 10⁻⁵ moles × 40.08 ] ÷ 100 mL. = 13.23 mg/L
In 100mL, the number of moles of Mg²⁺ = (total number of moles of EDTA solution used ) - ( number of moles of the EDTA solution in Ca²⁺ titration).
Also, The number of moles of Mg²⁺ = ( 0.0125 x 0.01087) - (3.30 x 10⁻⁵ moles.) = 1.031 x 10⁻⁴ moles.
The mass for the Mg²⁺ in the water sample = 1.031 x 10⁻⁴ moles x 24.305/0.1 = 25.06 mg/L.
12. In which layer of the sun do sunspots form?
A. Corona
B. Core
C. Convection zone
O D. Photosphere
Answer:
D
Explanation:
Photosphere is the layer where sunspots form.
Photosphere is the layer where sunspots form.
What is Photosphere?The Sun is made up of layers of material, like a baseball or rubber band ball. The photosphere is the lowest layer of the solar atmosphere. It is essentially the solar "surface" that we see when we look at the Sun in "white" (i.e. regular, or visible) light.
Like the Sun, our planet, Earth, is made up of layers, too. The thickest or most dense material on the Earth is in the very middle of our planet -- the core.
The thinnest is at the very top of our atmosphere - right next to outer space. The same is true of the Sun. But, the layers in the Sun and the Earth are much different.
Therefore, Photosphere is the layer where sunspots form.
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Suppose the reaction Ca3(PO4)2 + 3H2SO4 → 3CaSO4 + 2H3PO4 is carried out starting with 149 g of Ca3(PO4)2 and 86.9 g of H2SO4. How much phosphoric acid will be produced?
Answer:
57.9 grams .
Explanation:
Ca₃(PO₄)₂ + 3H₂SO₄ → 3CaSO₄ + 2H₃PO₄
1 mole 3 moles 2 moles
149 g of Ca₃(PO₄)₂ = 149 / 310 = .48 moles
86.9 g of H₂SO₄ = 86.9 / 98 = .8867 moles
Here H₂SO₄ is the limiting reagent .
.8867 / 3 = .2955
.2955 moles of Ca₃(PO₄)₂ reacts with .8867 mole of H₂SO₄ to give
2 x .2955 moles of H₃PO₄
H₃PO₄ produced = 2 x .2955 moles
= .591 moles
= .591 x 98 = 57.9 grams .
All organelles that only plant cells have
Answer:
Cell wall, chloroplast, and vacuoles
Explanation:
