Answer:
Approx. 38.61 grams
Chemistry B Semester Exam
An unknown substance has a boiling point of 174°C. Which statement is true about this unknown substance? (1 point)
-It has a lower boiling point than water, and it likely has stronger electrostatic forces between its molecules
than water.
-It has a higher boiling point than water, and it likely has stronger electrostatic forces between its molecules
than water.
-It has a lower boiling point than water, and it likely has weaker electrostatic forces between its molecules
than water.
-It has a higher boiling point than water, and it likely has weaker electrostatic forces between its molecules
than water.
Answer:
See below
Explanation:
Boiling point of water is 100 C
this substance is higher boiling point and the molecules are likely with higher e-static forces
The unknown substance has a higher boiling point than water, and it has stronger electrostatic forces between its molecules than water. Therefore, option B is correct.
Boiling point is a measure of the temperature at which a substance changes from a liquid to a gas phase. Substances with higher boiling points generally have stronger intermolecular forces, such as hydrogen bonding or stronger dipole-dipole interactions.
Since the boiling point of the unknown substance is higher than that of water (which boils at 100°C), it suggests that the unknown substance likely has stronger electrostatic forces between its molecules compared to water.
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Energy and Enthalpy Changes, Heat and Work -- Monatomic Ideal Gas dynamically generated plot 2.00-mol of a monatomic ideal gas goes from State A to State D via the path A→B→C→D: State A PA=11.0atm, VA=12.50L State B PB=11.0atm, VB=7.00L State C PC=25.0atm, VC=7.00L State D PD=25.0atm, VD=20.50L Assume that the external pressure is constant during each step and equals the final pressure of the gas for that step. Calculate q for this process. q = 1pts Tries 0/6 Calculate w for this process. w = -902 J Use w = -PΔV and sum over the individual steps. Check that you have the correct energy units and be sure you have the sign right (w is defined as the work done ON THE SYSTEM). 1pts Incorrect. Tries 4/6 Previous Tries Calculate ΔE for this process ΔE = 1pts Tries 0/6 Calculate ΔH for this process. ΔH = 1pts
(a) The heat generated in the process is 28 kJ.
(b) The work done in the process is determined as -28 kJ.
(c) The change in the internal energy is 0.
Heat of the isothermal compression
The heat generated in the process is negative done in the process.
W = -PΔV
W = -P(V₂ - V₁)
From A to BW = -P(VB - VA)
W = -11(7 - 12.5)
W = 60.5 L.atm = 60.5 x 101.325 J/L.atm = 6,130.16 J
From C to DW = -25(20.5 - 7)
W = -337.5 L.atm = -34,197.18 J
Total work , w = -34,197.18 J + 6,130.16 J = -28 kJ
q = - w
q = 28 kJ
Change in internal energyΔE = q + w
ΔE = 28 kJ - 28 kJ = 0
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Which of the following is the conjugate base of H3PO4?
2-
OA. HPO4²-
3-
O B. PO4³-
O C. H₂PO4
O D. H₂PO4+
Answer:
H2 PO4 -1 is the correct answer
An acid and a base which differ from each other by a proton are said to form a conjugate pair. Here the conjugate base of H₃PO₄ is H₂PO₄⁻. The correct option is C.
What is a conjugate base?The entity produced when acid gives up a proton has a tendency to regain the proton and hence it behaves as a base. It is called the conjugate base of the parent acid. A base is a substance which acts as a proton acceptor.
Here the conjugate base of H₃PO₄ is formed when a proton is lost from it. So the lose of one proton forms the molecule H₂PO₄⁻ which is the conjugate base. An acid is a proton donor.
When a base accepts a proton it has a tendency to donate the proton and hence behaves as an acid. It is called the conjugate acid of the parent base.
Thus the correct option is C.
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different between effort and load
Answer:
Is that load is a burden; a weight to be carried while effort is the work involved in performing an activity; exertion.Explanation:
mark me as brainlistCalculate AH for the reaction:
2N2 (g) + 6H20 (g) → 302 (g) + 4NH3(g)
Answer:
Explanation:
4NH₃ (g) + 3O₂ (g) ⇒ 2N₂ (g) + 6H₂ O(1)
Δ[tex]H_r={\sum}{ \Delta }H_f(\text{product})-{\sum}{ \Delta }H_f(\text{reactant})[/tex]
ΔH r =(2ΔH f(N 2 )+6ΔH f (H 2 O(l)))−(4ΔH f (NH 3 (g))+3ΔH f (O 2 (g)))
ΔH rex =[2×0+6×(−286)]−[4×(−46)+3×0]=−1716+186
ΔH rex =−1532kJ/mol
Thermodynamics is a branch of physical chemistry that studies heat and its effects and interactions. Governed by the four main laws, thermodynamics plays a huge role in physics and chemistry, and is also responsible for the law of conservation of energy, a fundamental rule in science.
The energy changes in two partial reactions are 225.3 kJ
and -432.0 kJ. The combined reaction is exothermic.
The combined reaction is exothermic , with the heat of reaction as -206.7 kJ
What is an Exothermic Reaction ?A reaction in which energy is liberated when reactants react to form products , The energy level of the reactant is more than that of the products.
The energy is liberated in the form of heat.
In the question it is given that
The energy changes in two partial reactions are 225.3 kJ and -432.0 kJ
The combined reaction is exothermic.
For the reaction to be exothermic the value of the heat of the reaction must be negative.
Summing the two energy changes will give us the heat of the combined reaction.
225.3 - 432.0
= -206.7 kJ
The combined reaction is exothermic , with the heat of reaction as -206.7 kJ.
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law and the rate constant for the reaction.
PLEASE HELP!!!!.
A buffer solution was prepared by mixing 150.00 mL of 1.1341 mol/L of CH3COOH
and 100.00 mL of 0.831 mol/L of barium acetate. Determine the pH of the buffer
solution after the addition of 10.00 mL of 0.010 mol sulphuric acid. Kc for acetic acid
is 1.8 x 10-5
The pH of the buffer solution after the addition of sulfuric acid is determined as 4.43.
Initial moles of acid and base
The initial moles of acid and base conjugate is determined as follows;
n = CV
na₁ = (150 x 1.1341)/1000
na₁ = 0.17 mol
nb₁ = (100 x 0.831)/1000
nb₁ = 0.083 mol
Number of moles of the acid addedH₂SO4 ⇄ 2H²⁺ + SO₄²⁻
na₂ = (10 x 0.01)/1000
na₂ = 0.0001 mol
Final number of moles of the acid and basenb = 0.083 - 2(0.0001) = 0.0829 mol
na = 0.17 + 2(0.0001) = 0.1702 mol
pH of the buffer solution[tex]Ka = \frac{[CH_3COO][H^+]}{[CH_3COOH]} \\\\1.8\times 10^{-5} = \frac{0.0829(H^+)}{0.1702} \\\\H^+ = \frac{(1.8 \times 10^{-5})(0.1702)}{0.0829} \\\\H^+ = 3.696 \times 10^{-5}\\\\pH = -Log [H^+]\\\\pH = -Log (3.696 \times 10^{-5})\\\\pH = 4.43[/tex]
Thus, the pH of the buffer solution after the addition of sulfuric acid is determined as 4.43.
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determine the number of gram of gas produced when 4.66 mole of water produced from the complete combustion of butane
.we can read the chemical preparation of the reaction as: "4 g of hydrogen react with 32 g of oxygen to give 36 g of water". :)
Please help.
Which organic product is formed in the reaction shown in the diagram?
The organic product formed in the reaction shown in the image would be bromoethane.
Substitution reaction in alkanesAlkanes, such as ethane undergoes a substitution reaction with halogens such as bromine to produce haloethanes.
For example, the equation of the reaction between ethane and bromine water is as below:
[tex]C_2H_6 + Br_2 --- > C_2H_5Br + HBr[/tex]
The products formed are bromoethane and hydrobromic acid.
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What volume of oxygen gas is needed for the complete combustion of 40.0 liters of hydrogen gas?
Answer:
2C2H6 + 7O2 ==> 4CO2 + 6H2O
When dealing with gases, it is possible to use liters and mols interchangeably.
So 4.00 L C2H6 x (7 mols O2/2 mols C2H6) = 4.00 x 7/2 = ? L O2
Explanation:
A solution of 0.20 M NaOH is used to prepare 0.10 M NaOH. How much of the 0.20 M solution is needed to prepare 455 mL of the diluted NaOH?
Taking into account the definition of dilution, 227.5 mL of the 0.20 M solution is needed to prepare 455 mL of the diluted NaOH.
What is DilutionDilution is the process of reducing the concentration of solute in solution, which is accomplished by simply adding more solvent to the solution at the same amount of solute.
In a dilution the amount of solute does not change, but as more solvent is added, the concentration of the solute decreases, as the volume (and weight) of the solution increases.
A dilution is mathematically expressed as:
Ci×Vi = Cf×Vf
where
Ci: initial concentrationVi: initial volumeCf: final concentrationVf: final volumeInitial volumeIn this case, you know:
Ci= 0.20 MVi= ?Cf= 0.10 MVf= 455 mLReplacing in the definition of dilution:
0.20 M× Vi= 0.10 M× 455 mL
Solving:
(0.10 M× 455 mL)÷ 0.20 M= Vi
227.5 mL= Vi
In summary, 227.5 mL of the 0.20 M solution is needed to prepare 455 mL of the diluted NaOH.
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What happens if i don’t pass the chemistry regent?
Answer:
You will typically get another chance to retake the exam
Answer:
well you either have a chance to retake the test if your teacher or just not let you take it at all. you have to pass 4 regents test including chemistry in order to get a regent diploma. so you can either retake or it you just failed it.
What is the mass of a cube that has a density of 45g/ml and a volume of 15 ml?
Answer:
675g
Explanation:
The equation that relates mass, density and volume is:
Density = mass ÷ volume
By rearranging the equation we can find the mass of the cube.
Mass = density × volume
Mass = 45 × 15
∴ Mass = 675 grams
Draw the product you expect from the reaction of (R)-2-bromooctane with -CH3CO2- and Br-.. Use the wedge/hash bond tools to indicate stereochemistry where it exists. Include H atoms at chiral centers only. If a group is achiral, do not use wedged or hashed bonds on it.
From the mechanism shown, the major product of the reaction is (S)-(+)-2-octanol.
What is an SN2 reaction?An SN2 reaction is one in which there is an inversion of configuration and the attack of the nucleophile occurs from behind the substrate.
As shown in the mechanism attached here, the major product of this reaction is (S)-(+)-2-octanol.
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Which of the following happens during an endothermic chemical change? (5 points)
Group of answer choices
Heat is released.
Net energy decreases.
Products have a higher total potential energy than the reactants.
Products have the same total potential energy as the reactants..
Answer: Products have a higher total potential energy than the reactants.
Explanation:
During endothermic reactions, energy is absorbed, meaning that the products will have more potential energy.
describe another way in which human activities that benefit society can also cause environmental risk.
59:27
Heat that flows by conduction is the transfer of thermal energy between substances in contact. What must occur for
this to happen?
O The two systems must be the same temperature.
The two systems must not be touching each another.
O One system must have higher kinetic energy than the other system.
O The thermal energy of one system must be the same as the thermal energy of the other system.
Answer:
O One system must have higher kinetic energy than the other system.
Explanation:
Higher KE of the system means hotter......the hotter will transfer heat to the cooler by conduction when they are in contact.
How can materials be classified on the basis of conduction of heat?
Explanation:
On the basis of electrical conductivity, materials are classified as conductors, semi-conductors and non-conductors. Conductors : Substances through which electricity can easily pass through are known as conductors. For example, copper, silver, mercury etc are good conductors of electricity
The food you eat can be broken into three main groups: _____, _____, and _____.
1 carbohydrates, fats, and vitamins
2 proteins, fats, and minerals
3 carbohydrates, fats, and proteins
4 proteins, vitamins, and minerals please help :)
Answer:
carbonhydrates, fats and ptoteins
Answer:3 carbohydrates, fats, and proteins
Explanation:
a gas measures 725mm and 32C. what will be the temperature of the gas at 705mm?
Answer:
31°C
Explanation:
Using the ratio, we can find the temperature of the gas at 705mm.
725mm : 32°C
705mm : x
[ x is the temperature we have to find ]
Cross multiply the ratios.
725x = 705 × 32
725x = 22560
x = [tex]\frac{22560}{725}[/tex] = 31°C
A student made a graph plotting the progress of a reaction over time. The student forgot to label the y-axis of the graph.
A graph is shown with two graph lines. One graph line starts at a higher position on the y axis and slopes downwards towards the right. The other graph line starts at a lower position on the y axis and slopes upwards towards the right. The two graph lines stop short of intersecting each other and continue as separate lines which gradually become straight and parallel to the x axis. A vertical line is shown at a point where the two graph lines finally became parallel to the x axis. This vertical line is labeled equilibrium. The title on the x axis is Time and an arrow pointing towards the right is shown above Time. The title on the y axis is left blank.
What best explains the label that the student should use on the y-axis? (5 points)
Group of answer choices
Amount, because as the amount of product decreases, the amount of reactant increases over time.
Reaction rate, because forward and backward reaction become equal at equilibrium.
Amount, because the amounts of reactants and products become constant after equilibrium is reached.
Reaction rate, as the rate of forward reaction increases and rate of backward reaction decreases over time.
Answer:
C
Explanation:
Recall that, at equilibrium, the concentration of the reactants and products stop changing because both the forward and reverse reaction rates are equal.
Therefore, Choice C is correct.
Choice A is incorrect because there is no indication that the upper line describes the products and the lower line describes the reactants.
Choice B is incorrect because the statement, while true, is not reflected by the graph. (The two lines after equilibrium are not at the same y-value.)
Choice D is incorrect because the forward reaction rate generally decreases as time increases due to the decrease in reactant concentration(s).
Lenses:
reflect light.
can only be concave.
do not have an optical axis.
None of the choices are correct.
Answer:
B. Can only be concave
Explanation:
Statement A is false because lenses do not reflect light. Lenses do have an optical axis.
How many moles of nitric acid are present in 50.0 g?
Answer:
3150.5g
Explanation:
1 mole of nitric acid weighs 63.01g
so i did 63.01g times 50.0g which equals 3150.5g
g= Grams
Hope This Helped
Answer:
0.79 moles
Explanation:
Formula :
Number of moles = Weight of substance / molecular mass
=============================================================
Here :
⇒ Weight of HNO₃ = 50 g
⇒ Molecular mass = 63 g
============================================================
Solving :
⇒ Number of moles = 50/63
⇒ Number of moles = 0.79 moles
What do the little numbers (subscripts) next to the lower right of each letter mean in the C₂H₄O₂?
Answer:
It represents the number of atoms of that particular element present in the compound. In C₂H₄O₂ there are 2 Carbon atoms, 4 Hydrogen atoms and 2 Oxygen atoms.
So I’m in 6th grade and this is a chart. I need the # of molecules, # of atoms in each element and the total # of atoms 2H₂SO
Answer:
1.) 2 molecules
2.) 4 H atoms, 2 S atoms, 2 O atoms
3.) 8 total atoms
Explanation:
1.) 2 H₂SO
--------> The molecule is all of the elements bonded together (H₂SO). Because there is a coefficient of 2 in front of the molecule, this means that there are 2 molecules present.
2.) 2 H₂S₁O₁
---------> The number of atoms of each element is determined by the subscripts and the coefficients. In one molecule, there is one oxygen, one sulfur, and 2 hydrogen atoms (denoted by subscripts). Because there are two molecules, these values are doubled.
3.)
--------> The total number of atoms is calculated by adding the number of atoms of each element. If between 2 molecules there are 4 hydrogens, 2 sulfurs, and 2 oxygens, combined there would be a total of 8 atoms.
what is the speed of light?can a object move in speed of light?
Answer:
The speed of light is the speed at which light travels. No, an object cannot move at the speed of light.
Explanation:
The speed of light is 186,000 miles per second. An object with mass cannot move at the speed of light since it would take an infinite amount of energy to achieve that velocity, since only massless particles can travel at the speed of light. Also, you would have to factor in air friction, meaning even if an object were to reach such high speeds, it would instantly disintegrate.
How is stoichiometry used to calculate energy absorbed when a mass of
liquid boils?
A. Grams liquid x mol/g x A Hreaction
B. Grams liquid x mol/g x A Hvap
OC. Grams liquid x mol/g x AHf
D. Grams liquid x mol/g x AHfusion
Answer: B. Grams liquid x mol/g x A Hvap
Stoichiometry used to calculate energy absorbed when a mass of liquid boils is Grams liquid × mol/g × ΔHvap.
What is Heat of vapourisation?It is the amount of heat evolved when mole of liquid is boiled to form vapours. It is a function of pressure according to which the change will happen in the reaction.
Given is that a particular mass of liquid is boiling.
We have supposed that heat of vapourisation for the same liquid is ΔHvap mol/g. Now if ΔHvap is the heat for 1 mole per gram of the liquid then if the mass of liquid is given,
Energy absorbed can be calculated as = Grams liquid × mol/g × ΔHvap
We should know that when a liquid boils it transforms into gaseous state and the process is called as Vapourisation.
Therefore, Stoichiometry used to calculate energy absorbed when a mass of liquid boils is Grams liquid × mol/g × ΔHvap.
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What type of reaction is shown below? Check all that apply.
2Mg+O2→2MgO
Answer:
synthesis reaction
Explanation:
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Question 4 of 10
Which statement best describes how scientists and engineers work together
in the research and development cycle?
OA. Scientists develop a theory, and then engineers perform
experiments to verify its accuracy.
B. Engineers do experiments to answer questions about nature, and
then scientists use the results to create a new technology.
OC. Scientists make designs based on engineering knowledge and
then make it available for public use.
D. Engineers develop a new technology, and then scientists use it to
make a new discovery.
Answer: Scientists make designs based on engineering knowledge and
then make it available for public use.
A sample of gas is collected in a flask with a volume of 267 mL at a pressure of 771 mmHg and a temperature of 21C. If the mass of the gas is 1.05 g, what is the molar mass of the gas?
Answer:
M=93.5g/mol
Explanation:
I did this in class and it was a review. :)