Best practices for fume hoods: work 25 cm inside, organize items to one side, use raised ledge; avoid open sash and quick movements.
Laboratory fume hoods must be used safely. Workers should operate at least 25 cm within the hood to preserve ventilation and avoid dangerous chemicals. Place things on one side of the hood to preserve ventilation and prevent clogging.
A raised ledge on the rear of the hood prevents things from falling in and impeding airflow. Avoid fully opening the sash to maintain ventilation and containment. Fast, rapid motions can interrupt airflow, so prevent them. These practises guarantee the fume hood contains harmful compounds, making the lab safer. Therefore, option (B), (D) and (E) are correct.
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A chemist collects hydrogen gas over water in an apparatus shown below. If the eudiometer reads 17.3800 mL of gas and has a total pressure of
95.090 mm Hg at 15.0°C, then how many moles of hydrogen gas were collected? (the vapor pressure of water at 15.0°C is 12.8 mm Hg)
Answer:
7.93 × 10⁻⁵ mol
Explanation:
Step 1: Calculate the pressure of hydrogen
The total pressure is the sum of the partial pressures of hydrogen and water vapor.
P = pH₂ + pH₂O
pH₂ = P - pH₂O
pH₂ = 95.090 mmHg - 12.8 mmHg = 82.3 mmHg
We can convert it to atm using the conversion factor 1 atm = 760 mmHg.
82.3 mmHg × 1 atm/760 mmHg = 0.108 atm
Step 2: Convert 15.0 °C to Kelvin
We will use the following expression.
K = °C + 273.15 = 15.0 + 273.15 = 288.2 K
Step 3: Calculate the moles of hydrogen
We will use the ideal gas equation.
P × V = n × R × T
n = P × V / R × T
n = 0.108 atm × 0.0173800 L / (0.0821 atm.L/mol.K) × 288.2 K
n = 7.93 × 10⁻⁵ mol
What is the biggest cause of change in Earth's systems?
A. Heat
B. Motion
C. Friction
D. Plate tectonics
Answer:
heat
Explanation:
because it's the cause of change
Answer:
heat
Explanation:
because it is a natural factor that causes the change in Earth's system
Explain why
when suger
is heated it
does not boil but rather break down
into carbon and water?
Answer:
When simple sugars such as sucrose (or table sugar) are heated, they melt and break down into glucose and fructose, two other forms of sugar. Continuing to heat the sugar at high temperature causes these sugars to lose water and react with each other producing many different types of compounds.
If the concentration of products is increased the equilibrium is shifted from * left to right/ to the left/ right to left /down left
Answer:
to the left
Explanation:
If the concentration of products is increased for a reaction that is in equilibrium, the equilibrium would shift to the left side of the reaction (the reactant's side).
For a reaction that is in equilibrium, the reaction is balanced between the reactants and the products. According to Le Cha telier's principle, if one of the constraints capable of influencing the rate of reactions is applied to such a reaction that is in equilibrium, the equilibrium would shift so as to neutralize the effects created by the constraint.
Hence, in this case, if the concentration of the products of a reaction in equilibrium is increased, the equilibrium would shift in such a way that more reactants are formed so as to annul the effects created by the increase in the concentration of the products. Since reactants are always on the left side of chemical equations, it thus means that the equilibrium would shift to the left.
To draw a Lewis structure for a polyatomic ion, begin by calculating A, the available electrons, and N, the needed electrons. What is N for CIO3-, the chlorate ion?
A = 26
N = ?
Answer:
16
Explanation:
Because the sum of all electron in that compound should be 41 and as it has one electron extra ,total no. of electrons are 42 .
So if we add 26 +16 we get 42
Hence it's correct answer
Write an essay on sensipar (cinacalcet)
Explanation:
The menstrual cycle is a reproductive cycle that takes place in the females of the group of primates. The menstrual cycle is divided into four phases:
(i) Menstrual phase: It extends from 1
st
to 4
th
day of the cycle. It occurs in the absence of fertilisation. During this phase, bleeding occurs as the endometrium of the uterus is sloughed off. The menstrual flow consists of secretion of endometrial glands, cell debris, unfertilized ovum. After 4
th
day, once again the FSH secretion from the pituitary is resumed and the new follicle starts developing.
(ii) Follicular phase: When the ovary is in this phase, the uterus enters in the proliferative phase. This takes place from 5
th
to 13
th
day of the cycle. During this phase new primordial follicle in the ovary develops due to the action of FSH from the pituitary. It gradually changes into the Graafian follicle and the production of estrogen starts. Only one follicle develops in one cycle. Corresponding to the changes in the ovary, the uterus also undergoes proliferation. Endometrial glands, stimulated by estrogen do repair process of the uterus.
(iii) Ovulatory phase: During this phase, ovulation takes place. It usually occurs on 14
th
day. Mature Graafian follicle ruptures due to LH secreted by the pituitary. Graafian follicle bursts and releases the ovum. This ovum along with the follicular fluid is picked up by the fimbriae of the infundibulum of the fallopian tube. It passes through the fallopian tube, where, if it happens to meet a sperm, it is fertilised. If not fertilised, the ovum degenerates.
(iv) Luteal phase: It corresponds with the secretory phase in the uterus. It takes place between 15
th
to 28
th
day of the cycle.
Ovarian changes: In the ovary, corpus luteum is formed from an empty Graafian follicle. Progesterone is secreted now. If the ovum is fertilised, corpus luteum is retained. LH and LTH from pituitary help in the maintenance of corpus luteum. If the ovum is not fertilised, corpus luteum degenerates and forms corpus albicans.
Uterine changes: Under the influence of progesterone, there is an increase in the thickness of the endometrium. Endometrial glands grow and become secretory. Progesterone is responsible for the maintenance of pregnancy. When fertilised ovum reaches the uterus, it is implanted and the placenta is formed. Till placenta becomes functional corpus luteum keeps on producing progesterone. But when progesterone source is cut off, endometrium sloughs off and menstruation begins
Which one of these statements is/are true: I. All redox reactions with positive emfs are spontaneous. II. If a redox reaction is spontaneous, it must be fast. III. A spontaneous redox reaction will have a cathode reaction that has a more negative reduction potential than the anode. III only. I and III are true. I only. II only. All of I, II, and III are true.
Answer:
yea all the answers are true
Redox reaction is the transfer of the electron from one species to another. All of the three statements are true about the redox reaction.
What is a redox reaction?A redox reaction is a type of chemical reaction in which the electrons are gained and lost by a species. The positive EMF of the cell results in spontaneous and will move the reaction in the forward direction.
In a redox reaction, the cathode reaction is comparatively more negative than the reduction potential present at the anode.
Therefore, option E. All I, II, and III are true.
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To prepare a standard (calibration) curve for a spectroscopy experiment, start by preparing ___________ with ______________ Then, measure the ______________ of each solution at _____________ and create a plot of ____________ for the measured values. Finally, find the best-fit line of the data set.
Answer: See explanation
Explanation:
The calibration curve is the method used for the determination of the concentration of a substance such that the unknown sample will be compared to some standard samples of the known concentration.
To prepare a standard (calibration) curve for a spectroscopy experiment, start by preparing (multiple solutions) with (different known concentrations). Then, measure the (absorbance) of each solution at (thesame wavelength) and create a plot of (absorbance vs. concentration) for the measured values. Finally, find the best-fit line of the data set.
Given the equation: 2C6H10(l) 17 O2(g) ---> 12 CO2(g) 10 H2O(g) MM( g/mol): 82 32 44 18 If 115 g of C6H10 reacts with 199 g of O2 and 49 g of H2O are formed, what is the percent yield of the reaction
Answer:
74%
Explanation:
Step 1: Write the balanced equation
2 C₆H₁₀(l) + 17 O₂(g) ⇒ 12 CO₂(g) + 10 H₂O(g)
Step 2: Determine the limiting reactant
The theoretical mass ratio (TMR) of C₆H₁₀ to O₂ is 164:544 = 0.301:1.
The experimental mass ratio (EMR) of C₆H₁₀ to O₂ is 115:199 = 0.578:1.
Since EMR > TMR, the limiting reactant is O₂.
Step 3: Calculate the theoretical yield of H₂O
The theoretical mass ratio of O₂ to H₂O 544:180.
199 g O₂ × 180 g H₂O/544 g O₂ = 65.8 g H₂O
Step 4: Calculate the percent yield of H₂O
%yield = (experimental yield/theoretical yield) × 100%
%yield = (49 g/65.8 g) × 100% = 74%
Answer:
Percentage yield of H₂O = 74.24%
Explanation:
The balanced equation for the reaction is given below:
2C₆H₁₀ + 17O₂ —> 12CO₂ + 10H₂O
Next, we shall determine the masses of C₆H₁₀ and O₂ that reacted and the mass of H₂O produced from the balanced equation. This is can be obtained as follow:
Molar mass of C₆H₁₀ = 82 g/mol
Mass of C₆H₁₀ from the balanced equation = 2 × 82 = 164 g
Molar mass of O₂ = 32 g/mol
Mass of O₂ from the balanced equation = 17 × 32 = 544 g
Molar mass of H₂O = 18 g/mol
Mass of H₂O from the balanced equation = 10 × 18 = 180 g
SUMMARY:
From the balanced equation above,
164 g of C₆H₁₀ reacted with 544 g of O₂ to produce 180 g of H₂O.
Next, we shall determine the limiting reactant. This can be obtained as follow:
From the balanced equation above,
164 g of C₆H₁₀ reacted with 544 g of O₂.
Therefore, 115 g of C₆H₁₀ will react to produce = (115 × 544)/164 = 381 g of O₂.
From the calculations made above, we can see that a higher mass (i.e 381 g) of O₂ than what was given (i.e 199 g) is needed to react with 115 g of C₆H₁₀.
Therefore, O₂ is the limiting reactant and C₆H₁₀ is the excess reactant.
Next, we shall determine the theoretical yield of H₂O. This can be obtained by using the limiting reactant as shown below:
From the balanced equation above,
544 g of O₂ reacted to produce 180 g of H₂O.
Therefore, 199 g of O₂ will react to produce = (199 × 180)/544 = 66 g of H₂O.
Thus, the theoretical yield of H₂O is 66 g.
Finally, we shall determine the percentage yield. This can be obtained as follow:
Actual yield of H₂O = 49 g
Theoretical yield of H₂O = 66 g
Percentage yield of H₂O =?
Percentage yield = Actual yield /Theoretical yield × 100
Percentage yield of H₂O = 49/66 × 100
Percentage yield of H₂O = 74.24%
The solubility of lithium fluoride, LiF, is 1.6 g/L, or 6.2 x 10â2 M.
a. Write the balanced solubility equilibrium equation for LiF.
b. Determine the molar concentration of the lithium ion and the fluoride ion.
c. Write the Ksp expression for the reaction.
d. Calculate Ksp for lithium fluoride.
Answer:
a. LiF(s) ⇄ Li⁺(aq) + F⁻(aq)
b. [Li⁺] = [F⁻] = 6.2 x 10⁻² M
c. Ksp = [Li⁺] [F⁻]
d. Ksp = 3.8 × 10⁻³
Explanation:
The solubility (S) of lithium fluoride, LiF, is 1.6 g/L, or 6.2 x 10⁻² M.
a. The balanced solubility equilibrium equation for LiF is:
LiF(s) ⇄ Li⁺(aq) + F⁻(aq)
b. We will make an ICE chart.
LiF(s) ⇄ Li⁺(aq) + F⁻(aq)
I 0 0
C +S +S
E S S
Then, [Li⁺] = [F⁻] = S = 6.2 x 10⁻² M
c. The solubility product constant, Ksp, is the equilibrium constant for a solid substance dissolving in an aqueous solution.
Ksp = [Li⁺] [F⁻]
d.
Ksp = [Li⁺] [F⁻] = (6.2 x 10⁻²)² = 3.8 × 10⁻³
Manganese-55 has _____neutrons.
55 Mn
25
A. 55
B. 30
C. 25
QUESTION:- Manganese-55 has _____neutrons.
OPTIONS :-
A. 55
B. 30
C. 25
ANSWER:- NUMBER OF NEUTRONS IS EQUAL TO THE DIFFERENCE BETWEEN THE MASS IF THE ATOM AND ATOMIC NUMBER
SO DIFFERENCE IS EQUAL TO :- 55-25 = 30 NEUTRONS.
SO THERE IS 30 NEUTRONS IN SINGLE ATOM OF THE MANGANESE-55 ATOM.
Answer:
the mass of an atom is the sum of proton and neutron which are both concentrated in nocleus of an atom. from the question the mass is given as 55 and the proton is 25.
Identify the true statements regarding hydrogen bonding. Select all that apply. Group of answer choices Hydrogen bonding occurs when a hydrogen atom is covalently bonded to an N, O, or F atom.
Answer:
True
Explanation:
Hydrogen bonding occurs when hydrogen is covalently bonded to a highly electronegative element such as N, O, or F.
Hydrogen bonding affects several physical properties of molecules in which it occur. For example, the high boiling point of water is caused by intermolecular hydrogen bonding irrespective of the low relative molecular mass of water.
The statement stating the presence of hydrogen bonding between the hydrogen and N, O, and F has been true.
Hydrogen bonding has resulted when the electrostatic interaction has been found in the atoms that have been more electronegative than the Hydrogen atoms.
The electrostatic force helps in attracting the atoms towards the hydrogen and thereby the hydrogen bonding takes place. It has been a weak force present in the molecules. The hydrogen bonding can be easily breakable.
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When a chemical changes from the solid phase to the gas phase, this is an example of What chemical property?
Answer:
sublimation
Explanation:
solid => liquid Melting
liquid => solid freezing
liquid => gas evaporation
gas => liquid condensation
solid => gas sublimation
gas => solid deposition (e.g.; formation of frost), however some scholars will also refer to this process as sublimation.
What is ethane?
A. A polymer
B. An alkyne
C. An alkane
D. An alkene
Answer:
D. An alkene
Explanation:
because Ethane is C2H4
Answer:
It's a alkANE. C.
Explanation:
The easiest way to memorize this is to look at the endings. Substances that end in -ANE are alkANEs. Substances that end in -ENE are alkENEs. Substances that end in -YNE are alkYNEs.
(a) (i) What is the name of apparatus used to measure conductivity of water
Answer:
An electrical conductivity meter (EC meter) measures the electrical conductivity in a solution. It has multiple applications in research and engineering, with common usage in hydroponics, aquaculture, aquaponics, and freshwater systems to monitor the amount of nutrients, salts or impurities in the water.
A sample of neon gas occupies 105 L at 27°C under a pressure of
985 torr. What volume would it occupy at standard condition
Answer: Volume occupied by given neon sample at standard condition is 123.84 L.
Explanation:
Given: [tex]V_{1}[/tex] = 105 L, [tex]T_{1} = 27^{o}C = (27 + 273) K = 300 K[/tex], [tex]P_{1}[/tex] = 985 torr
At standard conditions,
[tex]T_{2}[/tex] = 273 K, [tex]P_{2}[/tex] = 760 K, [tex]V_{2}[/tex] = ?
Formula used to calculate the volume is as follows.
[tex]\frac{P_{1}V_{1}}{T_{1}} = \frac{P_{2}V_{2}}{T_{2}}[/tex]
Substitute the values into above formula as follows.
[tex]\frac{P_{1}V_{1}}{T_{1}} = \frac{P_{2}V_{2}}{T_{2}}\\\frac{985 torr \times 105 L}{300 K} = \frac{760 torr \times V_{2}}{273 K}\\V_{2} = \frac{94116.75}{760} L\\= 123.84 L[/tex]
Thus, we can conclude that volume occupied by given neon sample at standard condition is 123.84 L.
QUESTION 11
Identify the reaction type.
KOH + HNO3 -> H2O + KNO3
O combustion
O decomposition
O combination
O single displacement
O double displacement
Determine the number of moles of aluminum in 2.154 x 10-1 kg of Al. Group of answer choices 5816 mol 7.984 mol 6.02 X 1023 mol 4.801 mol 8.783
Answer:
Avogadro's number is 1 mol = 6.02 * 10^23 elements
It means that 1 mol of atoms is 6.02 * 10^23 atoms
1 mol of atoms = 6.02 * 10^23 atoms
From there, if you divide both sides by 1 mol of atoms, you get
1 = 6.02 * 10^23 atoms / 1 mol of atoms.
That means, that to pass from a number of moles of atoms to number of atoms you have to multipby by the conversion factor
6.02*10^23 atoms Al/ 1 mol Al
That is the second option of the list.
Explanation:
Tapeworm is grouped in the phylum Platyhelminthes
Answer:
Tapeworm, also called cestode, any member of the invertebrate class Cestoda (phylum Platyhelminthes), a group of parasitic flatworms containing about 5,000 species. ... Tapeworms also lack a circulatory system and an organ specialized for gas exchange.
How many moles of p are needed to react with 30.1 moles of O2 SHOW the math below.
Answer:
information is missing
Explanation
reaction is needed to solve the problem
What is the concentration of Htions at a pH = 11?
mol/L
What is the concentration of Htions at a pH = 6?
mol/L
How many fewer Htions are there in a solution at a
pH = 11 than in a solution at a pH = 6?
A reactant. Q. decomposes at a second order. The slope of the graph 1/[Q] (1/M) vs time (s) is -0.04556. If the initial
concentration of Q for the reaction is 0.50 M, what is the concentration in M. of Q after 10.0 minutes?
Answer:
0.034 M
Explanation:
1/[A] = kt + 1/[A]o
[A] = ?
k= 0.04556
t= 10.0 minutes or 600 seconds
[A]o = 0.50 M
1/[A] = (0.04556 × 600) + 1/0.50
[A] = 0.034 M
Consider a galvanic (voltaic) cell that has the generic metals X and Y as electrodes. If X is more reactive than Y (that is, X more readily reacts to form a cation than Y does), classify the following descriptions by whether they apply to the X or Y electrode.
i. anode
ii. cathode
iii. electrons in the wire flow toward
iv. electrons in the wire flow away
v. cations from salt bridge flow toward
vi. anions from salt bridge flow toward
vii. gains mass
viii. loses mass
Answer:
X
anode
electrons in the wire flow away
anions from salt bridge flow toward
loses mass
Y
cathode
electrons in the wire flow toward
cations from salt bridge flow toward
gains mass
Explanation:
In a galvanic cell, oxidation occurs at the anode while reduction occurs at the cathode. The metal that is more reactive functions as the anode while the less reactive metal functions as the cathode.
Electrons leave the anode and travel via a wire to the cathode. At the anode cations give up electrons and enter into the solution.
At the cathode, cations pick up electrons and are deposited on the cathode leading to a gain in mass at the cathode.
Positive ions from the salt bridge flow towards the cathode while negative ions from the salt bridge flow towards the anode.
Which statement best describes what happens during a chemical reaction?
A. Reactants change into products.
B. Reactants change into new reactants.
C. Products change into reactants.
D. Products change into new products.
Answer:
A. Reactants change into products
When 3-methyl-1-pentene is treated with in dichloromethane, the major product is 1-bromo-3-methyl-2-pentene.
a. True
b. False
Answer:
True
Explanation:
When Methyl Pentene is introduced in a chemical reaction with dichloromethane then the major product will be bromomethylpentene. There can be small amount of bromo methyl pentene than the amount of methyl pentene introduced for reaction.
A monatomic ion with a charge of 2 has an electronic configuration of 1s22s22p6. This ion is a(n) _______ . What is the chemical symbol of the noble gas this ion is isoelectronic with
Answer:
A. Cation
B. Ne
Explanation:
The ion is positively charged by 2, making it a cation.
The electron configuration of the nearest noble gas Neon is 1s22s22p6
1. A monatomic ion with a charge of 2 has an electronic configuration of 1s22s22p6 is Neon.
2. chemical symbol of the noble gas is Kr (krypton).
Isoelectronic atom or ion has the same number of valence electrons. Krypton has 36 electrons and 36 protons (atomic number 36).
What is Neon?Neon is a chemical element with the symbol Ne and atomic number 10. It is a noble gas. Neon is a colorless, odorless, inert monatomic gas under standard conditions, with about two-thirds the density of air. It was discovered (along with krypton and xenon) in 1898 as one of the three residual rare inert elements remaining in dry air after nitrogen, oxygen, argon, and carbon dioxide were removed. Neon was the second of these three rare gases to be discovered and was immediately recognized as a new element of its bright red emission spectrum. The name neon is derived from the Greek word, the neuter singular form of (neos), meaning 'new'. Neon is chemically inert, and no uncharged neon compounds are known. The compounds of neon currently known include ionic molecules, molecules held together by van der Waals forces, and clathrates.
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A tank contains isoflurane, an inhaled anesthetic, at a pressure of 0.30 atm and 17.9°C. What is the pressure, in atmospheres, if the gas is warmed to a
temperature of 27.4°C, if n and V do not change?
Explanation:
here's the answer to your question
The pressure of the isoflurane gas at the temperature of 27.4 °C is 0.31 atm.
What is Gay Lussac's law?Gay-Lussac's law states that the pressure of a gas is directly proportional to the absolute temperature when the volume of the gas is kept constant.
Mathematically, Gay Lussca's law can be written as follows:
P/T = k
It is also expressed as the pressure of the gas being directly proportional to temperature.
P ∝ T (where V is constant)
or
[tex]\frac{P_1}{T_1} =\frac{P_2}{T_2}[/tex] ................(1)
Given, the initial pressure and initial temperature of the gas:
P₁ = 0.30 atm
and T₁ = 17.9 °C. = 17.9 + 273 = 290.9 K
The final temperature of gas T₂ = 27.4°C = 27.4 + 273 = 300.4 K
Now, from the equation (1): [tex]P_2=\frac{P_1\times T_2}{T_1}[/tex]
P₂ = (0.30) × (300.4)/290.0
P₂ = 0.31 atm
Therefore, the pressure of the isoflurane at 27.4°C is equal to 0.31 atm.
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what is the difference between Absorption and adsorption
một chất hữu cơ có cấu tạo c2h2 cho khí br2 vào ta được hỗn hợp khí
Answer:
C2H2 + Br2 → C2H2Br2
Explanation:
One crystalline form of silica (SiO2) has a cubic unit cell, and from X-ray diffraction data it is known that the cell edge length is 0.700 nm. If the measured density is 2.32 g/cm3, how many (a) Si4 and (b) O2- ions are there per unit cell
Answer:
There are 8Si atoms and 16 O atoms per unit cell
Explanation:
From the question we are told that:
Edge length [tex]l=0.700nm=>0.7*10^9nm[/tex]
Density [tex]\rho=2.32g/cm^3[/tex]
Generally the equation for Volume is mathematically given by
[tex]V=l^3[/tex]
[tex]V=(0.7*10^9)m^3[/tex]
[tex]V=3,43*10^-{22}cm[/tex]
Where
Molar mass of (SiO2) for one formula unit
[tex]M=28+32[/tex]
[tex]M=60g/mol[/tex]
Therefore
Density of Si per unit length is
[tex]\rho_{si}=\frac{9.96*10^{23}}{3.43*10^22}[/tex]
[tex]\rho=0.29[/tex]
Molar mass of (SiO2) for one formula unit
[tex]M=28+32[/tex]
[tex]M=60g/mol[/tex]
Therefore
There are 8Si atoms and 16 O atoms per unit cell
