Answer:
To transfer leftover solids to the filtration funnel and wash out crystals after recrystallization, ice cold methanol should be used (the mother liquor used for recrystallization).
Explanation:
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How to calculate the actual volume (ml) of water removed from the burette with water
density 1 g/ml:
i. 5mL of water removed
Answer:
Explanation:
The density of pure water is 1 gram per 1 milliliter or one cubic cm. By knowing the density of water we can use it in dilution equations or to calculate the specific gravity of other solutions.
It can also help us determine what other substances are made of using the water displacement experiment. This is done by observing how much water is displaced when an object is submerged in the water. As long as you know the density of the water, the mass of the object being submerged and the volume of increase you can calculate the density of the object.
This was done by the great Archimedes in discovering what composed the kings crown.
Which diagram correctly depicts the trend in electronegativity?
a.
b.
c.
d.
The electronegativity increases across the period and decreases down the group. Thus, option B is correct.
Electronegativity can be defined as the tendency of an atom to gain or attract an electron. The electronegativity has been dependent on the size of the atom, as well as the atomic number and valence electrons.
The atom with the requirement of a less number of atoms to complete its octet can easily gain the electron and thereby have high electronegativity. The atomic size also plays a role in the electronegativity of the atom.
The atom with a bigger size has the lesser force of attraction from the nucleus and thus has difficulty attracting the electron, however, the smaller size atom can easily attract the electron with the attraction force from the nucleus.
Thus, the elements with smaller sizes and a high number of valence electrons are more electronegative. In the periodic table, on moving from left to right the valence electrons increase, thus the electronegativity increases.
On moving down the group, the element size increase, thus the electronegativity decreases down the group.
The electronegativity increases across the period and decreases down the group. Thus, option B is correct.
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Which of the following lists describes characteristics of an acid? (3 points)
Bitter taste, high pH, and caustic
Sour taste, low pH, and dissolves metals
Sour taste, high pH, and dissolves metals
Slippery, low pH, and caustic
Acids have sour taste, low pH and dissolves metals.
The list that describes the characteristics of an acid is that it has sour taste, low pH, and dissolves metals.
Characteristics of an acidAn acid is a chemical substance that has the ability to donate hydrogen ions when involved in a chemical reaction.
The following are the characteristics or features of an acid:
They have a sour taste when tasted.When measured using a pH scale it is less than 7(low pH).They react with active metals to yield hydrogen gas.Therefore, the list that describes the characteristics of an acid is that it has sour taste, low pH, and dissolves metals.
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Suppose a 0.042M aqueous solution of phosphoric acid (H3PO4) is prepared. Calculate the equilibrium molarity of HPO4^−2.
Answer:
2.89x10⁻⁵M = [HPO₄²⁻]
Explanation:
The equilibrium of H3PO4 in water occurs H2PO4-:
H3PO4(aq) + H2O(l) ⇄ H3O⁺(aq) + H2PO4⁻(aq)
pKa = 2.16. And as pKa = -log Ka; Ka = 10^-2.16
Ka = 6.9183x10⁻³ = [H3O⁺] [H2PO4⁻] / [H3PO4]
As both [H3O⁺] and [H2PO4⁻] comes from the same equilibrium,
[H3O⁺]=[H2PO4⁻] :
[H3O⁺] = X
[H2PO4⁻] = X
[H3PO4] = 0.042 - X
Where X is reaction coordinate
Replacing:
6.9183x10⁻³ = [X] [X] / [0.042 - X]
6.9183x10⁻³ = X² / 0.042 - X
2.905686x10⁻⁴ - 6.9183x10⁻³X - X² = 0
Solving for X:
X = -0.02M. False solution. There is no negative concentration.
X = 0.014M. Right solution
[H2PO4⁻] = 0.014M
In the second equilibrium:
H2PO4⁻(aq) + H2O(l) ⇄ HPO4-(aq) + H3O+(aq)
Based on the same principles of the last equilibrium:
pKa2 = 7.21
Ka2 = 6.166x10⁻⁸ = [HPO4-] [H3O+] / [H2PO4⁻]
[HPO4-] = X
[H3O+] = X
[H2PO4⁻] = 0.014M - X
6.166x10⁻⁸ = X² / [0.014M - X]
8.3623x10⁻¹⁰ - 6.166x10⁻⁸X - X² = 0
Solving for X:
X = -0.0000289485. False solution.
X =
2.89x10⁻⁵M = [HPO₄²⁻]Answer True or False for each of the following statements. (a) The carburization surface was maintained at slightly less than 0.25 wt% carbon for each specimen. (b) Comparing the finished specimens at a depth of 0.20 mm, specimen A features the lowest carbon concentration. (c) Comparing the finished specimens as a whole, specimen D features the lowest overall amount of carbon.
Answer:
verdadero/a
falso/b
verdadero/c
Explanation:
A chemist measures the energy change
ΔH during the following reaction:
2NH3(g)→N2(g)+3H2(g)
ΔH=160kJUse the information to answer the following questions.This reaction is:__________.
a. endothermic
b. exothermic
Suppose 70.9 g of NH3 react. Will any heat be released or absorbed?
a. Yes, absorbed
b. Yes, released
c. No.
If you said heat will be released or absorbed in the second part of this question, calculate how much heat will be released or absorbed. Round your answer to 3 significant digits.
Answer:
For (1): The correct option is (a)
For (2): The correct option is (a) and 333.6 kJ of heat will be absorbed when 70.9 g of ammonia reacts.
Explanation:
There are 2 types of reactions that are classified based on enthalpy change:
Endothermic reactions: These are the reactions where heat is absorbed by the reaction. The change in enthalpy of the reaction, [tex]\Delta H_{rxn}[/tex] is positive for these reactions.
Exothermic reactions: These are the reactions where heat is released by the reaction. The change in enthalpy of the reaction, [tex]\Delta H_{rxn}[/tex] is negative for these reactions.
For (1):For the given chemical reaction:
[tex]2NH_3(g)\rightarrow N_2(g)+3H_2(g);Delta H=160kJ[/tex]
As the change in enthalpy or heat of the reaction is positive. Thus, the reaction is an endothermic reaction because heat is absorbed by the reaction.
For (2):When ammonia reacts, some amount of heat will be absorbed by the reaction. Thus, we can say the heat will be absorbed.
The number of moles is calculated by using the equation:
[tex]\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}[/tex] ......(1)
Given mass of ammonia = 70.9 g
Molar mass of ammonia = 17 g/mol
Using equation 1:
[tex]\text{Moles of ammonia}=\frac{70.9g}{17g/mol}=4.17mol[/tex]
By stoichiometry of the reaction:
If 2 mole of ammonia reacts, the heat absorbed is 160 kJ
So, if 4.17 moles of ammonia reacts, the heat absorbed will be = [tex]\frac{160kJ}{2mol}\times 4.17mol=333.6kJ[/tex]
Hence, 333.6 kJ of heat will be absorbed when 70.9 g of ammonia reacts
1. Arrange the following groups in order of decreasing priority that would allow you to determine E/Z, or R/S. Provide a string of letters (e.g. abcd) as an answer with the highest priority listed first, lowest priority last:
a) -CH3 b) -CH2OH c) -CH2NH2 d) -CH2BR
2. Arrange the following groups in order of decreasing priority that would allow you to determine E/Z, or R/S. Provide a string of letters (e.g. abcd) as an answer with the highest priority listed first, lowest priority last:
a) -F b) -CH2OH c) -CHO d) -CH3
1) The order of decreasing priority would allow determining E/Z or R/S is "dbca".
2) The order of decreasing priority would allow determining E/Z or R/S is "acbd".
What is absolute configuration?Absolute configuration can be described as to the spatial arrangement of atoms within a chiral molecular entity. Absolute configuration in organic molecules, where carbon is bonded to four different substituents.
The absolute configuration has used a set of rules to describe the relative positions around the chiral center atom. The most common labeling method is the descriptors R or S where R and S refer to Rectus and Sinister.
The group with the highest atomic number will get the highest priority and the group with the lowest atomic number substituents will get the lowest priority. Therefore, the order of priority is -CH₂Br > -CH₂OH > -CH₂NH₂ > -CH₃.
Therefore, the order of priority for the second part is -F > -CHO > -CH₂OH > -CH₃.
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Draw 2,3-dichloro octane
Answer:
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A sealed vessel initially contains 100 g of chlorine gas and 90 g of hydrogen gas. The two gases undergo reaction to form HCl. Which of the following statements is true?
a. 100 g HCl is produced
b. 190 g HCl is produced
c. less than 90 g HCl is produced
d. between 100 and 190 g of HCl is produced
Answer:
d.
Explanation:
H2 + Cl2 = 2HCL
From the equation 2g hydrogen combine with 71g of chlorine.
So 35.5 g Cl2 combines with 1g of H2
There are 100g of Cl2 so this will, by proportion, react with 100/35.5 g hydrogen.
This is 2.8 g hydrogen so the mass of HCl formed = 102.8 g.
The true statement is that d. between 100 and 190 g of HCl is produced.
How do find the mass of HCL?To find mass of HCL:
H2 + Cl2 = 2HCL
From the equation, 2g of hydrogen combines with 71g of chlorine.
So 35.5 g Cl2 combines with 1g of H2
There are 100g of Cl2 so this will, by proportion, react with 100/35.5 g of hydrogen.
This is 2.8 g hydrogen so the mass of HCl formed = 102.8 g.
Hydrogen chloride may be formed by the direct combination of chlorine (Cl2) gas and hydrogen (H2) gas.
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Draw the skeletal structure for: (E)-hept-5-en-2-one
Answer:
Draw the skeletal structure for: (E)-hept-5-en-2-one
Explanation:
The root word hept indicates that the given compound has seven carons in its longest chain.
-en- primary suffix indicates that the compound has one double bond in it.
2-one indicates that the compound has -C=O bond in the second carbon.
The prefix (E) indicates that the highest priority groups are on the opposite direction of the double bond.
The structure of the given molecule is:
Consider an acid-base titration in which the base is dispensed from a burette into a flask containing an acid. If any drops of the base adhere to the inner walls of the flask, but do not actually mix with the solution, the calculated acid concentration would be
Answer:
Higher than the actual value
Explanation:
Titration is a volumetric process in which a known volume of solution is dispensed from a burette to react with a known volume of solution in a conical flask.
When acid-base titration is carried out in such a way that the base is in the burette and the acid is in the conical flask and drops of the base adhere to the inner walls of the flask, but do not actually mix with the solution, the calculated acid concentration would be higher than the actual value.
This is because;
From CA= CBVBnA/VAnB
When VB(volume of base) that reacted is lower than the actual volume recorded, then the calculated volume of CA(concentration of acid) is much higher than the actual value since drops of the base adhere to the inner walls of the flask.
Which of the following statements correctly explains why bromination reactions are more selective than chlorination reactions.
a. bromine radical is less stable than chlorine radical, so it is more reactive and less choosy
b. bromine radical is more stable than chlorine radical, so it is more reactive and less choosy
c. bromine radical is more stable than chlorine radical, so it is less reactive and more choosy
d. bromine radical is less stable than chlorine radical, so it is less reactive and more choosy
e. relative radical stability is 3' radicals > 2" radicals> 1 radicals when bromine radicals snatch hydrogens from alkanes, but when chlorine radicals snatch hydrogens the resulting alkyl radical stability is 3 radicals < 2 radicals< 1' radicals
Answer: A bromine radical is more stable than chlorine radical, so it is less reactive and more choosy.
Explanation:
A chlorine atom being more electronegative in nature is able to attract a hydrogen atom more readily towards itself as compared to a bromine atom.
Since bromine is less electronegative in nature so bromine will be more selective as a hydrogen abstracting agent. As a result, bromine radical is more stable in nature than chlorine radical.
Thus, we can conclude that bromine radical is more stable than chlorine radical, so it is less reactive and more choosy.
g Consider two different liquids at atmospheric pressure: hexane and water. Hexane has a higher vapor pressure than water. As a result, the temperature at which hexane will boil will be [ Select ] water and its vapor pressure when it is boiling will be [ Select ] water when water is boiling.
Answer:
Lower than
Higher than
Explanation:
The vapour pressure and boiling point of liquids are inversely related. Thus, the higher the vapour pressure of a liquid, the lower it's boiling point. Lower vapour pressure implies that the liquid is easily converted into vapour phase.
If hexane has a higher vapour pressure than water then its boiling point is lower than that of water and its vapor pressure when it is boiling will be higher than water when water is boiling.
Qual número atômico do ferro?
Answer:
The answer is Iron.
Explanation:
I hope this helps you out. Have a nice day!
An ionic compound contains an unknown ion X and has the formula X3N2. Ion X contains 10 electrons. Write down the chemical symbol of X?
Answer:
Mg3N2
Explanation:
it would be magnesium as it would loss to electron so it would have 10 electron. you can see in the picture above .
hope this helps :)
Calculate the number of ATOMS in 1.0 mole of O2. blank x 1024
Answer:
6.023*10^23........ .......
What is oxygen's half-equation?
answer; 1/ 20_2[2-] +2e - ->0.
A product of homolytic fission can never be
a - charged
b - nucleophile
c- both
d-none of these
Answer:
both
Explanation:
A homolytic fission is said to have occurred when the breakage of a bond between two atoms leaves each of the bonding atoms with equal number of electrons. Homolytic fission often results in the creation of radicals.
Since homolytic fission yields two species with equal number of electrons(usually odd number of electrons), the products of such process can not be charged. They can not be nucleophiles because nucleophiles need to possess two electrons which can be shared with another chemical specie.
When taking a measurement with a pH meter, keep the instrument in the _______storage solution or water until it is needed. Rinse the pH meter with
_______deionized water or acetone and gently pat dry. Place the meter in the sample solution, and record the measurement when the pH _______stabilizes or reaches the maximum value
Answer:
storage solution , deionized water, stabilizes
Explanation:
A pH meter is a scientific device or instrument that is used to measure the pH of a given aqueous solution thereby determining the nature of the solution whether it is acidic or basic or neutral.
While using the pH meter or taking the measurement using the pH meter --
it should be kept in a storage solution for effective working.Before using the device, it is rinsed with a deionized water and pat dry.Record the measurements when the pH meter stabilizes.How many liters of hydrogen can be produced at a pressure of 2 atm and a temperature of 298 K
Answer:
1.17 L of H₂
Explanation:
We'll begin by calculating the number of mole in 2.3 g of Mg. This can be obtained as follow:
Mass of Mg = 2.3 g
Molar mass of Mg = 24 g/mol
Mole of Mg =?
Mole = mass /molar mass
Mole of Mg = 2.3 / 24
Mole of Mg = 0.096 mole
Next, we shall determine the number of mole of H₂ produced by the reaction of 2.3 g (i.e 0.096 mole) of Mg. This can be obtained as follow:
Mg + 2HCl —> MgCl₂ + H₂
From the balanced equation above,
1 mole of Mg reacted to 1 mole of H₂.
Therefore, 0.096 mole of Mg will also react to produce 0.096 mole of H₂.
Finally, we shall determine volume of H₂ produced from the reaction. This can be obtained as follow:
Number of mole (n) of H₂ = 0.096 mole
Pressure (P) = 2 atm
Temperature (T) = 298 K
Gas constant (R) = 0.0821 atm.L/Kmol
Volume (V) of H₂ =?
PV = nRT
2 × V = 0.096 × 0.0821 × 298
Divide both side by 2
V = (0.096 × 0.0821 × 298) /2
V = 1.17 L
Therefore, 1.17 L of H₂ were obtained from the reaction.
Classify each of the following as a strong acid or a weak acid and indicate how each should be written in aqueous solution. Classify ... In solution this acid should be written as: weak 1. hydrocyanic acid H3O CN- _______ 2. hydrobromic acid
Answer:
HCN, weak acid
H⁺, Br⁻, strong acid
Explanation:
Hydrocyanic acid is a weak acid, according to the following equation.
HCN(aq) ⇄ H⁺(aq) + CN⁻(aq)
Thus, it should be written in the undissociated form (HCN).
Hydrobromic acid is a strong acid, according to the following equation.
HBr(aq) ⇒ H⁺(aq) + Br⁻(aq)
Thus, it should be written in the ionic form (H⁺, Br⁻).
Underneath the ocean floor, methane can exist as a solid known as methane hydrate. Methane hydrate forms when large amounts of methane become trapped in the crystal structure of water, which develops into a solid similar to ice. A scientist working for a deep water drilling company is studying the properties of the three different phases of methane: methane hydrate, liquified natural gas, and natural gas. Which of the properties is true
Answer:
Methane is present in solid, liquid and gaseous form.
Explanation:
Methane hydrate is present in solid state when the hydrogen-bonded water and methane gas come into contact at high pressures and low temperatures in the deep oceans while on the other hand, methane which is present inside the earth surface in gaseous form due to non-availability of water that can combine with methane. Methane is also found in liquid form when it is cool with high pressure and low temperature.
1. Show that heat flows spontaneously from high temperature to low temperature in any isolated system (hint: use entropy change that occurs during the process for your proof).
2. Work out the entropy change for the decomposition of mercuric oxide using mathematical and graphical arguments.
Answer:
1 ) Δs ( entropy change for hot block ) = - Q / th ( -ve shows heat lost to cold block )
Δs ( entropy change for cold block ) = Q / tc
∴ Total Δs = ΔSc + ΔSh
= Q/tc - Q/th
2) ΔSdecomposition = Δh / Temp = ( 181.6 * 10^3 / 773 ) = 234.928 J/k
Explanation:
1) To show that heat flows spontaneously from high temperature to low temperature
example :
Pick two(2) solid metal blocks with varying temperatures ( i.e. one solid block is hot and the other solid block is cold )
Place both blocks for time (t ) in an insulated system to reduce heat loss or gain to or from the environment
Check the temperature of both blocks after time ( t ) it will be observed that both blocks will have same temperature after time t ( first law of thermodynamics )
Δs ( entropy change for hot block ) = - Q / th ( -ve shows heat lost to cold block )
Δs ( entropy change for cold block ) = Q / tc
∴ Total Δs = ΔSc + ΔSh
= Q/tc - Q/th
2) Entropy change for Decomposition of mercuric oxide
2HgO (s) → 2Hg(l) + O₂ (g)
Δs = positive
there is transition from solid to liquid and the melting point of mercury ( the point at which reaction will take place ) = 500⁰C
hence ΔSdecomposition = S⁻ Hg - S⁻ HgO =
Δh of reaction = 181.6 KJ
Temp = 500 + 273 = 773 k
hence ΔSdecomposition = Δh / Temp = ( 181.6 * 10^3 / 773 ) = 234.928 J/k
Nickel + oxygen = nickel oxide. What is the balanced redox reaction?
Answer:
This is an oxidation-reduction (redox) reaction:
2 Ni0 - 4 e- → 2 NiII
(oxidation)
2 O0 + 4 e- → 2 O-II
(reduction)
Ni is a reducing agent, O2 is an oxidizing agent.
Give your familiarity for following terms
1. roasting 2. smelting 4. zone refining 5. polling
Answer:
The roasting process is a delicate combination of art and science . Roasters are familiar with how the beans look and the smells Well, familiarity with the machine makes things much easier to predict, but the best way is to do many different tests .Well, familiarity with the machine makes things much easier to predict, but the best way is to do many different tests.Smelting is a process of applying heat to ore in order to extract a base metal. It is a form of extractive metallurgy. It is used to extract many metals from their ores, including silver, iron, copper, and other base metals.In zone refining, solutes are segregated at one end of the ingot in order to purify the remainder, or to concentrate the impurities. For example, in the preparation of a transistor or diode semiconductor, an ingot of germanium is first purified by zone refining. In zone refining, solutes are segregated at one end of the ingot in order to purify the remainder, or to concentrate the impurities. ... For example, in the preparation of a transistor or diode semiconductor, an ingot of germanium is first purified by zone refining.Polling is the process where the computer or controlling device waits for an external device to check for its readiness or state, often with low-level hardware. For example, when a printer is connected via a parallel port, the computer waits until the printer has received the next character.Explanation:
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Green plants use light from the Sun to drive photosynthesis, a chemical reaction in which liquid water and carbon dioxide gas form aqueous glucose (CH1206) and oxygen (O2) gas. Calculate the moles of glucose produced by the reaction of 2.40 mol of carbon dioxide. Be sure your answer has a unit symbol, if necessary, and round it to 3 significant digits.
Answer:
.
Explanation:
What is the volume of a flask containing 0.199mol of Cl2at a temperature of 313K and a pressure of 1.19atm
Answer:
43.0 L
Explanation:
Step 1: Given and required data
Moles of chlorine gas (n): 0.199 molTemperature (T): 313 KPressure (P): 1.19 atmIdeal gas constant (R): 0.0821 atm.L/mol.KStep 2: Calculate the volume of the flask (V)
We will use the ideal gas equation.
P × V = n × R × T
V = n × R × T / P
V = 1.99 mol × (0.0821 atm.L/mol.K) × 313 K / 1.19 atm = 43.0 L
The answer is 4.30 L
What is the cell potential of an electrochemical cell that has the half-reactions shown below?
Ag⁺ + e⁻ → Ag
Fe → Fe³⁺ + 3e⁻
Answer:
E°(Ag⁺/Fe°) = 0.836 volt
Explanation:
3Ag⁺ + 3e⁻ => Ag°; E° = +0.800 volt
Fe° => Fe⁺³ + 3e⁻ ; E° = -0.036 volt
_________________________________
Fe°(s) + 3Ag⁺(aq) => Fe⁺³(aq) + 3Ag°(s) ...
E°(Ag⁺/Fe°) = E°(Ag⁺) - E°(Fe°) = 0.800v - ( -0.036v) = 0.836 volt
A chemist measures the amount of iodine solid produced during an experiment. He finds that of iodine solid is produced. Calculate the number of moles of iodine solid produced. Round your answer to significant digits.
The question is incomplete, the complete question is:
A chemist measures the amount of iodine solid produced during an experiment. He finds that 8.31 g of iodine solid is produced. Calculate the number of moles of iodine solid produced. Round your answer to the correct number of significant digits.
Answer: The number of moles of solid iodine produced is 0.0327 moles
Explanation:
The number of moles is defined as the ratio of the mass of a substance to its molar mass. The equation used is:
[tex]\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}[/tex] ......(1)
Given mass of solid iodine = 8.31 g
Molar mass of solid iodine = 253.8089 g/mol
Plugging values in equation 1:
[tex]\text{Moles of solid iodine}=\frac{8.31g}{253.8089g/mol}=0.0327mol[/tex]
Hence, the number of moles of solid iodine produced is 0.0327 moles
Silver has two naturally occurring isotopes with the following isotopic masses: 10747Ag 10947Ag 106.90509 108.9047 The average atomic mass of silver is 107.8682 amu. The fractional abundance of the lighter of the two isotopes is ________.
Answer: The fractional abundance of lighter isotope is 0.518
Explanation:
Average atomic weight is the sum of the masses of the individual isotopes each multiplied by its fractional abundance. The equation used is:[tex]\text{Average atomic weight}=\sum_{i=1}^{n}\text{(Atomic mass of isotope)}_i\times \text{(Fractional abundance)}_i[/tex] ......(1)
Let the fractional abundance of Ag-107 isotope be 'x'
For Ag-107 isotope:Atomic mass = 106.90509 amu
Fractional abundance = x
For Ag-109 isotope:Atomic mass = 108.9047 amu
Fractional abundance = (1 - x)
Average atomic mass of silver = 107.8682 amu
Plugging values in equation 1:
[tex]107.8682=(106.90509 \times x) + (108.9047 \times (1-x))\\\\107.8682=106.90509x+108.9047-108.9047x\\\\1.99961x=1.0365\\\\x=0.518[/tex]
Fractional abundance of Ag-107 isotope (lighter) = x = 0.518
Hence, the fractional abundance of lighter isotope is 0.518
