The enthalpy of formation (ΔHf) of [tex]Br_2[/tex](g) at 1.00 atm and 298 K is 0 kJ/mol. Hence, option A is correct.
What does ΔHf mean?The standard enthalpy of formation is defined as the enthalpy change for creating one mole of a compound from elements in their standard states.
The enthalpy of formation (ΔHf) of [tex]Br_2[/tex] (g) at 1.00 atm and 298 K is 0 kJ/mol.
It is because the enthalpy of formation of the molecule is only 0 in its standard state and for bromine, the standard state at 298K is the liquid state.
Hence, option A is correct.
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Answer:
A: The Δ.Hf for Br2(I) is 0 kJ/mol.
C: The Δ.Hf for Hg(I) is 0 kJ/mol.
D: The Δ.Hf for Cl2(g) is 0 kJ/mol.
Explanation:
what are the four types of severe storms
Storms are disturbances in atmospheric conditions. The four severe storms are thunderstorms, lightning, heavy rain, and blizzards.
What are blizzards?Blizzards are the type of storm that includes high wind at 40 km/h and also have snow and cold air that makes the temperature drop and causes poor visibility.
Thunderstorms and lightning occur with high electrical charge release during high wind and rain. Heavy rains are severe types of storms as they can cause a flood.
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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
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.
Calculate the how many sodium atoms must react completely to give 33,6 dm³ hydro-
gen gas at STP.
2Na+ 2H₂O → 2NaOH + H₂(g)
To give 33.6 dm³ hydrogen gas at STP, 18.06 x 10²³ atoms of Na must react completely.
What is Mole concept ?A mole is a unit of measurement used to measure the amount of any fundamental entity (atoms, molecules, ions) present in the substance.
As according to the given equation, 2 moles (ie 12.04 x 10²³ atoms) of Na-atoms produces 1 mole (22.4 ltr) of H₂-gas.
Hence, to produce 33.6 ltr (equivalent to 33.6 dm³) of H₂-gas produced by ;
= 12.04 x 10²³ atoms of Na / 22.4 ltr of H₂-gas x 33.6 ltr
= 18.06 x 10²³ atoms of Na
Hence, To give 33.6 dm³ hydrogen gas at STP, 18.06 x 10²³ atoms of Na must react completely.
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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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a 40 g sample of water absorbs 500 calories of energy, how much did the water temp changed?
2.99 °C is the change in temperature if a 40 g sample of water absorbs 500 calories of energy.
What is specific heat capacity?The specific heat capacity is defined as the quantity of heat (J) absorbed per unit mass (kg) of the material when its temperature increases 1 K (or 1 °C), and its units are J/(kg K) or J/(kg °C).
Given data:
m = 40 g
Q = 500 J
Specific heat capacity of water = 4.18 J/g°C
Change in Temperature =?
The formula for Heat Energy is given by:
Q = mcp∆T
where: Q - Heat Energy
m - mass
cp - specific heat
∆T = change in temperature, [tex]T_2 - T_1[/tex]
Solution:
Substituting the value of m, specific heat capacity of water and Q in the formula,
500 J = (40 g)(4.18 J/g°C)(∆T)
∆T = 2.99 °C
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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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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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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.
The theory of relativity is stated as the equation E=mc² where:
E-energy
m = mass
c=speed of light
A scientist has data for the speed of light and energy variables. What form of the equation should the scientist use to determine the mass of an
object?
Answer:
don't know mass? or energy just search
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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What is the Percentage abundance of an isotope
Answer:
It is the proportion of atoms of an isotope in a sample of an element taken from the natural world.
Explanation:
The molecular geometry of the PF3 molecule is __________, and this molecule is ________.
O tetrahedral, unipolar
O trigonal pyramidal, nonpolar
O trigonal pyramidal, polar
O trigonal planar, nonpolar
O trigonal planar, polar
Answer:
C.) trigonal pyramidal, polar
Explanation:
Around the phosphorus central atom, there are 3 fluorine atoms and 1 lone pair. This makes the shape tetrahedral, but gives it a trigonal pyramidal geometry. The lone pair on the phosphorus disrupts the balance of the molecule and pulls the electrons towards it. This makes the molecule polar.
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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0.58 mol of Mg contains how many atoms? please show work
The number of atoms present in 0.58 mole of magnesium, Mg is 3.49×10²³ atoms
Avogadro's hypothesis1 mole of Mg = 6.02×10²³ atoms
How to determine the atoms in 0.58 mole of Mg1 mole of Mg = 6.02×10²³ atoms
Therefore,
0.58 mole of Mg = 0.58 × 6.02×10²³
0.58 mole of Mg = 3.49×10²³ atoms
Thus, 3.49×10²³ atoms are present in 0.58 mole of Mg
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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).
Is the chemical reaction faster when the metal is in dust form or when it's melted?
Answer:
dust form
Explanation:
because dust spreads alot faster
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.
Name one similarity and one difference between visible light and sound.
Answer:
Light and sound both are waves, but sound requires a material medium to travel, and hence cannot travel in empty space while light can travel through vacuum but not through opaque materials. Both undergo refraction, diffraction and interference.
Explanation:
What forms white light?
Combination of all the wavelengths of ultraviolet light
Combination of all the wavelengths of visible light
Absorption of electromagnetic rays
Absorption of infrared rays
Answer:
Combination of all the wavelengths of visible light.
Explanation:
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Chemical equation of isopropyl alcohol and ethanoic acid
Answer:
chemical formula of isopropyl alcohol can also be written as: C3H7OH, CH3CHOHCH3 or (CH3)2CHOH.
chemical formula of ethanoic acid is CH₃COOH.
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 the volume of 0.10 g of titanium (4.51 g/cm³).
The volume of titanium with mass of 0. 10g and density of 4. 51 g/cm³ is 0. 02 cm³
What is volume?Volume is known to be equal to the mass divided by the density.
It is written thus:
Volume = Mass / density
How to calculate the volumeThe volume is calculated using the formula:
Volume = mass ÷ density
Given the mass = 0. 10g
Density = 4.51 g/cm³
Substitute the values into the formula
Volume of titanium = 0. 10 ÷ 4.51 = 0. 02 cm³
Thus, the volume of titanium with mass of 0. 10g and density of 4. 51 g/cm³ is 0. 02 cm³
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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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do you guys have an answer?
Answer:
5095
Explanation:
Answer:
the first pups are very similar in color so i would assume that the mom and dad are some color and breed, rather the second example would be a white and black dog with possible other colors between black and white
Explanation:
It took 55 days for a radioactivity of 1.75 x 1012 Bq to remain 0.135 Ci. What is the half-life of this radioactivity?
From the calculations, the half life of the material is 6.5 days.
What is radioactivity?The term radioactivity has to do with the spontaneous disintegration of a specie.
Uisng the formula;
N=Noe^-kt
N= amount at time t = 0.135 Ci or 4.995 ×10^9 Bq
No = amount initially present = 1.75 x 10^12 Bq
k = rate constant = ?
t = time taken = 55 days
Hence;
4.995 ×10^9 = 1.75 x 10^12e^-55k
4.995 ×10^9/1.75 x 10^12 = e^-55k
2.85 * 10^-3 = e^-55k
ln2.85 * 10^-3 = -55k
k = ln2.85 * 10^-3/-55
k = 0.1066 day-1
Half life = 0.693/ 0.1066 day-1
= 6.5 days
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Which changes involve forming or breaking chemical bonds?
burning and digesting
boiling and melting
burning and melting
rusting and cutting
Answer: burning and digesting
Both of these are chemical changes.
Answer:
burning and digesting
Explanation:
All of the following reactions are described as decomposition reactions except
O CuSO4.5H₂O(s) CuSO4(s) + 5H₂O(g).
O 2PbO₂ (s)
2PbO(s) + O₂(g).
O Fe(CO)(I)
Fe(s) + 5CO(g).
O H₂SO3(aq)
SO₂(g) + H₂O(l).
O NO₂(g) + H₂O(l) 4 NO(g) + 2HNO3(aq).
The reaction NO₂(g) + H₂O(l) 4 NO(g) + 2HNO3(aq) is not a Decomposition Reaction , Option E is the correct answer.
What is a Decomposition Reaction ?A reaction in which a substance break down into two or more substances is called a Decomposition Reaction.
In the given question
the reactions
CuSO4.5H₂O(s)--> CuSO4(s) + 5H₂O(g).
2PbO₂ (s) --> 2PbO(s) + O₂(g).
Fe(CO)(I)-->Fe(s) + 5CO(g).
H₂SO3(aq)-- >SO₂(g) + H₂O(l)
These are all Decomposition Reaction.
The only reaction which is not is the Reaction E
NO₂(g) + H₂O(l) 4 NO(g) + 2HNO3(aq)
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2. Calculate the mass, in grams, for 3.47 moles of each of the following:
a. lead(II) acetate
b. sodium chloride
Explanation:
1 moles Lead(II) Acetate to grams = 325.28804 grams
3.47 moles Lead(II) Acetate to grams = 325.28804 ×3.47 grams=1128.749 grams
1 moles sodium chloride to grams=58.5 grams
3.47 moles sodium chloride to grams=58.5×3.47 grams
=202.995 grams
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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