Coal and Energy obtained from coal are formed as a result of decomposed life matter such as plants
A. Compressed ancient plants
Fossil FuelsIt should be noted that coal is also a type of fossil fuel formed by prolong compaction of fossil material e.g dead plants over millions of years, forest lives etc. and as a result of high pressure and heat acting on these fossil matter they are transformed to fuel.
In summary, fossil fuels are formed as a result of age long compressed matter.
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How many grams of solid sodium cyanide should be added to 1.00 L of a 0.119 M hydrocyanic acid solution to prepare a buffer with a pH of 8.809
Answer:
1.62 g
Explanation:
Given that:
Concentration of HCN = 0.119 M
Assuming the ka 4.00 × 10⁻¹⁰
The pKa of HCN (hydrocyanic acid) = -log (Ka)
= - log ( 4.00 × 10⁻¹⁰)
= 9.398
pH of buffer = 8.809
Using Henderson Hasselbach equation:
[tex]pH = pKa + log \dfrac{[conjugate\ base ]}{acid}[/tex]
[tex]pH = pKa + log \dfrac{[CN^-]}{[HCN]}[/tex]
[tex]8.809 = 9.398 +log \dfrac{[CN^-]}{[HCN]}[/tex]
[tex]log \dfrac{[CN^-]}{[HCN]}= 8.809 - 9.398[/tex]
[tex]log \dfrac{[CN^-]}{[HCN]}= -0.589[/tex]
[tex]\dfrac{[CN^-]}{[HCN]}= 0.2576[/tex]
[CN^-] = 0.2576[HCN]
[CN^-] = 0.2756 (0.119) L
[CN^-] = 0.033 M
∴
The amount of NaCN (sodium cyanide) is calculated as follows:
[tex]= 1.00 L \times \dfrac{0.033 \ mol \ NacN }{1 \ L } \times \dfrac{49.01 \ g}{1 \ mol \ of \ NacN}[/tex]
= 1.62 g
How are elements with similar properties grouped in the periodic table?
A. In the same half
B. In the same column
C. In the same row
D. In the same box
AAnswer:A
Explanation:
Write the bond line formula for the compound (CH3)2CHCH2C(CH3)3.
Formula is (CH3)2CHCH2C(CH3)3 and the name is 2,2,4-trimethylpentane
When stirred in 30°C water, 5 g of powdered potassium bromide, KBr, dissolves faster than 5 g of large crystals of potassium bromide. Which of the following best explains why the powdered KBr dissolves faster?
A. Potassium ions and bromide ions in the powder are smaller than potassium ions and bromide ions in the large crystals.
B. Powdered potassium bromide exposes more surface area to water molecules than large crystals of potassium bromide.
C. Fewer potassium ions and bromide ions have been separated from each other in the powder than in the crystals.
D. Powdered potassium bromide is less dense than large crystals of potassium bromide.
Answer:
B
Explanation:
Do diện tích tiếp xúc ở dạng bột cao hơn dạng tinh thể
A student measures her computer keyboard with a meter stick and finds that it has a width of 47.35 cm. Which statement about this measurement is true?
PLZZZZ HELP
A.) All the numbers are certain
B.) The 4 is uncertain
C.) The 5 is somewhat uncertain
D.) The 5 is certain
A chemistry student must write down in her lab notebook the concentration of a solution of sodium thiosulfate. The concentration of a solution equals the mass of what's dissolved divided by the total volume of the solution.
Answer:
A chemistry student must write down in her lab notebook the concentration of a solution of sodium thiosulfate. The concentration of a solution equals the mass of what's dissolved divided by the total volume of the solution.
Explanation:
The concentration of a solution can be measured in terms of molarity.
The molarity of a solution can be defined as the number of moles of solute present in the total volume of the solution.
The number of moles of solute is the ratio of mass of solute to molar mass of solute.
Hence,
[tex]Molarity=\frac{mass of solute}{molar mass of solute} * \frac{1}{volume of solution in L.}[/tex]
One mole of
C
2
H
6
O
C
2
H
6
O has two moles of Carbon (C), six moles of Hydrogen (H) and one mole of Oxygen (O). How many moles of Hydrogen is in 0.2 moles of
C
2
H
6
O
C
2
H
6
O?
Answer:
c
no need to thank me okay
A chemist requires a large amount of 1-bromo-4-phenyl-2-butene as starting material for a synthesis and decides to carry out the following NBS allylic bromination reaction in the presence of UV light. Draw the structures of all of the observed products.
NBS
(C6H5)CH2CH = CHCH3 → ?
CCI4
Draw one additional resonance structure for the species below:
CH3CH=CHCH=CHCH=CHCH2
Answer:
CH 2 CH 3 CHCH = C6H5 + 5 Hydrogen Atoms
I hope I helped you.
Deepest apologies if I was wrong!
Bye!
~ Myaka O.
examples of isotones
Answer:
Examples of isotones include carbon-12, nitrogen-13 and oxygen-14. These atoms all have six neutrons and six, seven and eight protons respectively. A mnemonic that can be used to differentiate isotones from isotopes and isobars is as follows: same Z (number of protons) = isotopes.
The products in a decomposition reaction _____. are compounds can be elements or compounds are elements include an element and a compound
Answer:
compounds are elements include an element and a compound
Explanation:
elements in the decomposition reaction is the substance that cannot be separated into simpler substances. Compounds, technically act as a reactant in the decomposition reaction, but since the reaction breakdown one substance into two or more, sometimes it exists in the product
Compound A has a partition coefficient (K) of 7 when comparing its solubility in CH2Cl2 to water ( K=11, [solubility of A in g/ml in CH2Cl2] divided by [solubility of A in g/ml in H2O]). If we take 17.0 g of A and partition it thoroughly between 150 ml of CH2Cl2 and 100 ml of water, what is the equation which will tell us how much of A (which is represented by x) is in the water layer after this partitioning ?
Answer:
The equation which will tell us how much of A that is mis inmthe water layer after partitioning is: 7 = (17 - x) g / 150 mL ÷ x g /100 mL
Explanation:
A partition coefficient is the ratio of the concentration of a substance in one solvent phase to the concentration in a second solvent phase when the two concentrations are at equilibrium. Usually the two phases are an organic phase and an aqueous phase. Thus, the partition coefficient K, of a compound is the ratio of the compound's concentration in the organic layer compared to the aqueous layer.
K = C₁/C₂ at equilibrium
In the compound A given, CH₂Cl₂ is the organic phase while water is the aqueous phase
Amount of A that is partitioned in between dichloromethane, CH₂Cl₂ and water, H₂O is 17.0 g
Let the amount of A that is dissolved in water be x g
Solubility of A in water given in g/mL = (x / 100) g/ml
Amount of A dissolved in dichloromethane, CH₂Cl₂ = (17 - x) g
Solubility of A in dichloromethane, CH₂Cl₂ given in g/mL = (17 - x/150) g/mL
Since the partition coefficient, K of compound A when comparing its solubility in CH₂Cl₂ to water is 7, that is;
K = [solubility of A in g/ml in CH₂Cl₂] / [solubility of A in g/ml in H2O] = 7
The equation for the amount of A in the water layer is given as follows:
7 = (17 - x) g / 150 mL ÷ x g /100 mL
Solving for x
7 = (17 -x) × 100 / 150x
7 × 150x = (17 - x) × 100
1050x = 1700 - 100x
1150x = 1700
x = 1700/1150
x = 1.48 g
The rate of the reaction is 1.6*10-2 M/s when the concentration of A is 0.15 M. Calculate the rate constant if the reaction is (a) first order in A and (b) second order in A.
Answer:
[tex]k_1=0.107s^{-1} \\\\k_2=0.711M^{-1}s^{-1}[/tex]
Explanation:
Hello there!
In this case, according to the given information and the attached picture in which we can see the units of the rate constant, it turns out possible for us to realize the two called rate laws are:
[tex]r=k[A]\\\\r=k[A]^2[/tex]
The former is first-order and the latter second-order; in such a way, we solve for the rate constant in both cases to obtain the following:
[tex]k=\frac{r}{[A]}=\frac{1.6x10^{-2}M/s}{0.15M}=0.107s^{-1} \\\\k=\frac{r}{[A]^2}=\frac{1.6x10^{-2}M/s}{(0.15M)^2}=0.711M^{-1}s^{-1}[/tex]
Regards!
B. It shifts the equilibrium toward the right, favoring product.
11. What is meant by the term heat of reaction?
A. the difference in temperature between products and reactants
B. the difference in bond energies between products and reactants
C. the difference in heat energies between products and reactants
What other name is a synonym for this term?
A. entropy change
B. potential change
C. enthalpy change
Answer:
11) the difference in heat energies between products and reactants
12) enthalpy change
Explanation:
The heat of reaction is defined as that energy released or absorbed as chemical substances participate in a chemical reaction. It is a term used to denote the change in energy as reactants change into products.
Another name of heat of reaction is enthalpy of reaction. It is a state function since it depends on the initial and final states of the system.
The pH of a solution with a hydrogen-ion concentration of 4.90 x 10-'Mi
Please answe I’ll give you brainliest
Answer:
pH < 7; pH = 7; pH > 7
Explanation:
when dealing with an acidic base, you have the formula for [H3O+] > [OH-] which yields a pH < 7.
when you have a neutral base, the reactive ion concentration would be [H3O^+] = [OH^-] which yields a pH = 7.
finally, when dealing with a basic classification, the formula would be [H3O^+] < [OH^-] yields a pH > 7.
Which of the following reasons explains why if salt water is heated, the water turns into steam while the salt remains?
Water and salt have an equal boiling point.
Water has a lower boiling point than salt.
Salt has a lower boiling point than water.
Salt and water have an equal melting point.
If the salt water is heated, the water turns into steam and the salt remains because the water has a lower boiling point than the salt.
The following points can be considered:
The boiling point is defined as the temperature at which the substance turns into the gaseous state from the liquid state.The boiling point of water is [tex]100^{o} C[/tex].The salt is a substance comprising two entities separated by the opposite charges with ionic interactions.The boiling point of a salt is higher than the boiling point of the water.The process involved when salt water is heated:
The salt water mixture when heated, the water turns into steam at [tex]100^{o} C[/tex]But the salt remains until it reaches its boiling temperature. If the salt is soluble in water and is then heated, then there occurs an elevation in the boiling point of the substance, due to the presence of the salt.Therefore, the answer is water has a lower boiling point than salt.
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For a particular first-order reaction, it takes 48 minutes for the concentration of the reactant to decrease to 25% of its initial value. What is the value for rate constant (in s -1) for the reaction
Answer: The value for rate constant for a reaction is [tex]4.81\times 10^{-4} s^{-1}[/tex]
Explanation:
The integrated rate law equation for first-order kinetics:
[tex]k=\frac{2.303}{t}\log \frac{a}{a-x}[/tex] ......(1)
Let the initial concentration of reactant be 100 g
Given values:
a = initial concentration of reactant = 100 g
a - x = concentration of reactant left after time 't' = 25 % of a = 25 g
t = time period = 48 min = 2880 s (Conversion factor: 1 min = 60 s)
Putting values in equation 1:
[tex]k=\frac{2.303}{2880s}\log (\frac{100}{25})\\\\k=4.81\times 10^{-4} s^{-1}[/tex]
Hence, the value for rate constant for a reaction is [tex]4.81\times 10^{-4} s^{-1}[/tex]
A steel with a critical fracture toughness of 150 MPa.m1/2 has a yield strength of 1500 MPa. If fracture were to take place at the yield stress, answer the following questions.
Surface crack size at yielding leading to failure is:_____________.
a. 0.497 cm
b. 0.994 cm
c. 0.32 cm
Answer:
c.
Explanation:
From the given information:
Critical fracture toughness [tex]K_{IC}[/tex] = 150 MPa.[tex]m ^{1/2}[/tex]
yield strength [tex]\sigma[/tex] = 1500 MPa
surface crack size [tex]a_c[/tex] = ???
The formula for the fracture toughness is can be expressed as:
[tex]K_{IC}= \sigma \sqrt{\pi a_c}[/tex]
replacing our values to solve for the surface crack size, we have:
[tex]150= 1500 \sqrt{\pi a_c}[/tex]
[tex]\dfrac{150}{ 1500} = \sqrt{\pi a_c}[/tex]
[tex]\dfrac{0.1}{1.77} = \sqrt{ a_c}[/tex]
[tex]a_c[/tex] = 0.0564²
[tex]a_c[/tex] = 0.0032 m
[tex]a_c[/tex] = 0.32 cm
Fossils of a dinosaurs would most likely be found in
A)
conglomerate rock
B) sedimentary rock
C)
Igneous rock
D)
metamorphic rock
Answer:
b
Explanation:
Answer:
B
Explanation:
Using Hess’s law, what is the standard enthalpy of formation of manganese (II) oxide, MnO(s)?
With the help of hess's law:
ΔHf(MnO)=−248.9 kJ−12(272.0) kJ=−384.9 kJ(per mole) Δ H f ( M n O ) = − 248.9 k J − 1 2 ( 272.0 ) k J = − 384.9 k J ( p e r m o l e )
What is Hess's law?Hess's law of constant heat summation, also known simply as Hess' law, is a relationship in physical chemistry named after Germain Hess, a Swiss-born Russian chemist and physician who published it in 1840.
Moreover, hess's Law of Constant Heat Summation (or just Hess's Law) states that regardless of the multiple stages or steps of a reaction, the total enthalpy change for the reaction is the sum of all changes.
Therefore, hess' law is based on the state function character of enthalpy and the first law of thermodynamics. Energy (enthalpy) of a system (molecule) is a state function.
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if 7.90 mol of C5H12 reacts with excess O2, how many moles of CO2 will be produced by the following combustion reaction?
Answer:
If 7.9 moles of C₅H₁₂ reacts with excess O₂, 39.5 moles of CO₂ will be produced.
Explanation:
The balanced reaction is:
C₅H₁₂ + 8 O₂ → 5 CO₂ + 6 H₂O
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:
C₅H₁₂: 1 moles O₂: 8 molesCO₂: 5 moles H₂O: 6 molesThen you can apply the following rule of three: if by stoichiometry 1 mole of C₅H₁₂ produces 5 moles of CO₂, then 7.9 moles of C₅H₁₂ will produce how many moles of CO₂?
[tex]amount of moles of CO_{2} =\frac{7.9 moles of C_{5}H_{12}*5 moles of CO_{2} }{1 mole of C_{5}H_{12} }[/tex]
amount of moles of CO₂= 39.5 moles
If 7.9 moles of C₅H₁₂ reacts with excess O₂, 39.5 moles of CO₂ will be produced.
Fabric A is used to rub a wooden rod. A second piece of Fabric A is used to rub an ebonite rod. It is observed that the wooden rod and the ebonite rod attract one another. What can you say about the position of Fabric A in the electrostatic series in relation to wood and ebonite?
Fabric A is likely to be a material that has a moderate tendency to gain electrons when in contact with other materials and is lower in the electrostatic series than ebonite but higher than wood.
What is electrostatic series?The electrostatic series is a list of materials ranked in order of their tendency to gain or lose electrons when in contact with another material.
Materials higher in the series tend to lose electrons more readily and become positively charged, while materials lower in the series tend to gain electrons more readily and become negatively charged.
Ebonite is a synthetic polymer that is known to become negatively charged when rubbed, and it is typically placed near the top of the electrostatic series.
Wood, on the other hand, is a poor conductor of electricity and does not readily become charged when rubbed. Based on these facts, we can infer that Fabric A is lower in the electrostatic series than ebonite, but higher than wood.
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An OH group attached to a hydrocarbon is called a _________ group whereas ______________ is a polyatomic ion with a charge of _______.
An OH group attached to a hydrocarbon is called an alkyl group whereas hydroxide is a polyatomic ion with a charge of -1.
What is OH group?OH group is also called hydroxyl group. Alcohol is a type of organic compound that is characterized by one or more hydroxyl (―OH) groups attached to a carbon atom of an hydrocarbon chain so we can conclude that an OH group attached to a hydrocarbon is called an alkyl group whereas hydroxide is a polyatomic ion with a charge of -1.
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A stain is made up of molecules that do not have charged regions. What soap/solvent combination should I use?Are there multiple?
Answer:
The answer is below
Explanation:
Yes, there are multiple combinations.
Firstly, a solvent or soap combination could be used as a polar solvent with soap. In this way, the nonpolar region of the soap molecules would mix directly with the stain while the solvent would surround the soap-stain micelle.
Secondly, another method or way is to have a combination of a nonpolar solvent with no soap. In this method, however, it is the solvent that would mix directly with the stain.
Which reaction produces an insoluble product?
A
2KI + Pb(NO )2 → → PbI, + 2KNO
B
2AgNO3 + Ca(CH,02)2 + Ca(NO3)2 + 2AgC,H,O,
C
3BaCl2 + ALLS
→ 2AlCl3 + 3BaS
.
D
SrBr, + Mg(OH)2 → MgBr, + Sr(OH)2
Answer: The correct option is A).
Explanation:
Precipitation reaction is defined as the reaction where a solid precipitate (solid substance) is formed at the end of the reaction. It is insoluble in water.
For the given chemical reactions:
A): [tex]2KI+Pb(NO_3)_2\rightarrow PbI_2+2KNO_3[/tex]
The iodide of lead is generally insoluble in water. Thus, lead iodide is a precipitate.
B): [tex]2AgNO_3+Ca(CH_3COO)_2\rightarrow Ca(NO_3)_2+2CH_3COOAg[/tex]
The nitrates and acetates of all metals are soluble in water.
C): [tex]3BaCl_2+Al_2S_3\rightarrow 2AlCl_3+3BaS[/tex]
The sulfide of barium is soluble in water.
D): [tex]SrBr_2+Mg(OH)_2\rightarrow MgBr_2+Sr(OH)_2[/tex]
The hydroxide of strontium is soluble in water.
Hence, the correct option is A).
An atom of 24/11 na decays by gamma decay which atom is left after the decay
Answer:
Hello There!!
Explanation:
The atom is still 24Na.
hope this helps,have a great day!!
~Pinky~
The acid dissociation constant, Ka, of HNO3 is 4.0 x104. What does the ka
value indicate about this compound?
A. HNO3 is neither an acid nor a base,
B. HNO3 is a strong acid.
C. HNO3 is a weak acid
D. HNO3 is a strong base.
Answer:
i thing its b
Explanation:
The acid dissociation constant (Ka) is a measure of the strength of an acid in solution. In HNO₃ (nitric acid), the given Ka value is 4.0 x 10⁴. It represents the equilibrium constant for the dissociation reaction of an acid in water. Therefore, option B is correct.
The dissociation constant often denoted as Kd, is a measure of the strength of the interaction between a ligand and a receptor or between a substrate and an enzyme.
A high Ka value indicates a strong acid, while a low Ka value indicates a weak acid. In this case, the Ka value of 4.0 x 10⁴ for HNO₃ is relatively high.
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Describe why corrosion is a natural process
Answer :
Answer :because it happens due to moisture and oxygenDuring a reaction in an aqueous solution, the concentration of bactants
decreases and the amount of products increases. How do these changes in
concentration affect the reaction rate?
A. The reaction rate decreases.
B. The reaction rate varies unpredictably.
C. The reaction rate increases.
D. The reaction rate stays the same.
Answer:
my define it will be turst me is c
The half life for the radioactive decay of potassium-40 to argon-40 is 1.26×109 years. Suppose nuclear chemical analysis shows that there is 0.359 mmol of argon-40 for every 1.000mmol of potassium-40 in a sample of rock. Calculate the age of the rock.
Answer:
2.42x10⁹ years is the age of the rock
Explanation:
The decay of an isotope follows the equation:
Ln[A] = -kt + Ln[A]₀
Where [A] is amount of isotope after time t, k is decay constant and [A]₀ is the initial amount of the isotope
To find decay constant from half-life:
k = ln2 / half-life
k = ln2 / 1.26x10⁹years
k = 5.501x10⁻¹⁰ years⁻¹
As in the reaction, K-40 produce Ar-40:
[A] = 0.359mmol
[A]₀ = 0.359mmol + 1.000mmol = 1.359mmol
Replacing:
Ln[0.359mmol] = -5.501x10⁻¹⁰ years⁻¹t + Ln[1.359mmol]
-1.3312 = -5.501x10⁻¹⁰ years⁻¹t
t = 2.42x10⁹ years is the age of the rock
A student collecting CaCO3 produced by the reaction of Na2CO3(aq) and CaCl2(aq) obtains a percent yield of 81%. Choose all of the following observations that could explain the low yield.
a. The combined reactants were not stirred before filtering the precipitate.
b. The student did not completely dry the precipitate before weighing it.
c. The precipitate was not washed prior to drying.
d. A rubber policeman was not used to scrape precipitate from the beaker.
e. The filter paper was not wetted with water prior to filtering the precipitate.
Answer:
a, d and e. are true.
Explanation:
The reaction that occurs is:
Na2CO3(aq) + CaCl2(aq) → CaCO3(s) + 2NaCl
In ideal conditions, the percent yield of the reaction must be 100%. All explanations about why the student could not collect all precipitate are right:
a. The combined reactants were not stirred before filtering the precipitate. Not stirring could not promote all the reaction. TRUE.
b. The student did not completely dry the precipitate before weighing it. If the student don't dry the precipitate, the mass of precipitate must be higher producing a percent yield > 100%. FALSE.
c. The precipitate was not washed prior to drying. Produce more mass. FALSE.
d. A rubber policeman was not used to scrape precipitate from the beaker. If the student doesn't collect all the precipitate the percent yield could be < 100%.. TRUE.
e. The filter paper was not wetted with water prior to filtering the precipitate. TRUE. If you don't wet the filter paper you can lose a part of precipitate from the walls of this one.
