Answer:
The answer to the question is 78
Answer:
78
Explanation:
In rounding off to two, we consider the third digit. if it is more than five we ad one to the second digit otherwise we truncate.
in the case of 77.616, we add one to the second digit and truncate the rest.
Suppose you obtain 0.500 g of a compound after synthesis with the following solubility: In ethanol 4.24g/100 mL at 78 ⁰C and 0.30g/100 mL at 0 ⁰C. Performing recrystallization to purify the compound using 10 mL of ethanol, what would you expect the theoretical yield from the experiment to be? Show your calculations. (6 points)
Answer:
0.394g
Explanation:
At 78°C, you can dissolve, in 10mL of ethanol, 0.424g of the compound will dissolve. Then, you must filter the solution.
You take the filtrate of the solution in ethanol and cool it to 0°C. Om mL, only 0.03g of the compound will remain in solution. The other part is the purified compound.
Its mass (Theoretical yield) is:
0.424g - 0.030g =
0.394gIn carbon NMR, the carbon atom of the carbonyl group in aldehydes and ketones has a chemical shift of about:
Answer:
Its a shift of about 200ppm
Explanation:
because we know that a chemical shift explains the resonating frequency of a particular nucleus in relation to its standard as in a magnetic field so that
carbonyl group in aldehydes and ketones is 200ppm
Using standard reduction potentials from the ALEKS Data tab, calculate the standard reaction free energy for the following redox reaction. Round your answer to significant digits. N2H4 + 4OH + 2Cl2
Answer:
-973 KJ
Explanation:
The balanced reaction equation is;
N2H4(aq) + 2Cl2(g) + 4OH^-(aq)---------> 4Cl-(aq) + 4H ^+(aq) + 4OH^-(aq) + N2(g)
Reduction potential of hydrazine = -1.16 V
Reduction potential of chlorine = 1.36 V
From;
E°cell= E°cathode - E°anode
E°cell= 1.36 - (-1.16)
E°cell= 2.52 V
∆G°=- nFE°cell
n= number of moles of electrons = 4
F= Faraday's constant = 96500 C
E°cell = 2.52 V
∆G°=- (4 × 96500 × 2.52)
∆G°= -972720 J
∆G°= -972.72 KJ
The bond angles in H3O are less than____________ and greater than_______.
Answer:
104.5 and 109.5
Explanation:
Bond angle is the angle formed between three atoms which has at least two bonds present between them. The number of lone pairs in a covalent bond is a determinant of the bond angle as the lone pairs which are negatively charged repulses the bond pairs thereby creating a distortion and angle.
Studies have however shown that the bond angles in H3O are lesser than 109.5 and greater than 103.5. This provides a bond range of H3O.
How can people conserve water at home? rinsing dishes with cool water instead of warm water
washing dishes only when the dishwasher is full
Why was 1990 an important year regarding air quality?
O The United States took first steps to keep the air clean.
O The United States created the Environmental Protection Agency.
Modifications and improvements were made to the Clean Air Act.
O Funding was established under the Clean Air Act to study air pollution.
Answer:
The United States took first steps to keep the air clean.
Explanation:
The US environmental protection agency was created in the year 1970 so this option is wrong.
November 15, 1990 however was a milestone in keeping the air clean, the signing f the amendments, the amendments set the stage for protecting the ozone layer, improving air quality and visibility.
The correct option is option A; The United States took first steps to keep the air clean.
Answer:
C. Modifications and improvements were made to the Clean Air Act.
Explanation:
The Clean Air act was originally established in 1970 and was concerned with the aim of protecting people and the environment in general from polluted air. Polluted air could cause different illnesses and environmental degradation.
The law was amended in 1990 in which modifications and improvements were made to the Clean Air Act. There was the need to reduce acid rain, toxic emissions which could deplete the ozone layer and cause varying respiratory illnesses in humans and to increase visibility.
How many significant figures are in the quantity 12.0 mL?
O A. 1
B. 2
C. 3
O D. 12
Answer:
C. 3
Explanation:
12.0 - 3 significant figures 1,2 and 0, because 0 is after decimal point.
You are making a 0.2M solution of sodium acetate in the lab. Sodium acetate has a molecular mass of 82.03 g/mol. How many g of sodium acetate will you use if you are making 500mL of the solution
Answer: The answer can be found on CHEG
Explanation:
What voltage would have been observed if you had switched the position of the electrodes but not the solutions for any of the electrochemical cells
This question is incomplete, the complete question is;
An electrochemistry lab was conducted. What voltage would have been observed if you had switched the position of the electrodes but not the solutions for any of the electrochemical cells? (e.g. placed Cu electrode with Zn²+ and Zn with Cu²+).
Clearly explain your answer, include what would have happened in each cell
Answer:
E°cell = +1.10V
Explanation:
At lower reduction potential, electrode acts as an anode ( -ve )
At higher reduction potential, electrode acts as a cathode ( +ve )
NOW
standard reduction of Cu⁺² / Cu electrode,
E° cu⁺²/cu = 0.34V
standard reduction potential of zn⁺² / zn electrode,
E° zn⁺/zn = -0.76V
Zn has lower reduction potential, therefore it acts as an anode and standard reduction potential of Cu has higher reduction potential so it acts as a cathode.
now we know that
E°cell = E°cathode - E°anode
we substitute
E°cell = 0.34V - ( -0.76V)
E°cell = +1.10V
Therefore there is no flow of e- in the wire when the copper electrode placed in Zn²⁺ ( electrode reverse). When zinc electrode placed in copper solution, copper deposition in zinc electrode takes place, so zinc is converted into Zn ion and no flow of e- will occur in outer circuit.
∴ The voltage becomes zero
In a cathode ray tube, electrons flow from the negatively charged cathode to the positively charged anode. Cathode ray tubes may be small and compact, but they typically must be plugged in to function. The flow of electrons within this tube is:________.
a. spontaneous
b. nonspontaneous
c. neither spontaneous nor nonspontaneous
d. impossible to tell
Answer:
spontaneous
Explanation:
Electrons in a cathode ray tube are produced at the cathode and move towards the anode which is the the positive electrode.
This flow of electrons is spontaneous because electrons flow from a point of negative electric potential to a point of positive electric potential, hence the answer above.
For each of the following nuclei, determine the binding energy per nucleon (in MeV). (For all masses, keep six places beyond the decimal point when performing your calculations. Then round your final answer to at least three significant figures.)(a) 21 MeV (b) 4He MeV (c) 180 MeV (d) 23Na MeV
Answer: (a) BE = 1.112 MeV
(b) BE = 7.074 MeV
(c) BE = 7.767 MeV
(d) BE = 8.112 MeV
Explanation: Binding energy per nucleon is the average energy necessary to remove a proton or a neutron from the nucleus of an atom. It is mathematically defined as:
[tex]BE = \frac{\Delta m.c^{2}}{A}[/tex]
Where
Δm is a difference in mass known as mass defect
A is atomic mass of an atom.
Mass Defect is determined by:
[tex]\Delta m =Zm_{p}+(A-Z)m_{n} - m_{nuc}[/tex]
where:
Z is atomic number
[tex]m_{p}[/tex] is mass of proton
[tex]m_{n}[/tex] is mass of neutron
[tex]m_{nuc}[/tex] is mass of the nucleus
Mass of proton is 1.007825u.
Mass of neutron is 1.008665u.
The unit u is equal to 931.5MeV/c².
(a) 2H(deuterion): Given: Z = 1; A = 2; [tex]m_{nuc}[/tex] = 2.014102u
[tex]\Delta m =1(1.007825)+1(1.008665) -2.014102[/tex]
[tex]\Delta m =0.002388u[/tex]
[tex]BE = \frac{0.002388.c^{2}}{2}.931.5\frac{MeV}{c^{2}}[/tex]
BE = 1.112MeV
(b) 4He (Helium): Given: Z = 2; A = 4; [tex]m_{nuc}[/tex] = 4.002603
[tex]\Delta m =2(1.007825)+2(1.008665) -4.002603[/tex]
[tex]\Delta m =0.030377u[/tex]
[tex]BE = \frac{0.030377.c^{2}}{4}.931.5\frac{MeV}{c^{2}}[/tex]
BE = 7.074MeV
(c) 18O (Oxygen): Given: Z = 8; A = 18; [tex]m_{nuc}[/tex] = 17.999160
[tex]\Delta m =8(1.007825)+10(1.008665) -17.999160[/tex]
[tex]\Delta m =0.15009u[/tex]
[tex]BE = \frac{0.15009.c^{2}}{18}.931.5\frac{MeV}{c^{2}}[/tex]
BE = 7.767MeV
(d) 23Na (Sodium): Given: Z = 11; A = 23; [tex]m_{nuc}[/tex] = 22.989767
[tex]\Delta m =11(1.007825)+12(1.008665) -22.989767[/tex]
[tex]\Delta m =0.200288u[/tex]
[tex]BE = \frac{0.200288.c^{2}}{23}.931.5\frac{MeV}{c^{2}}[/tex]
BE = 8.112MeV
Convert 1,650,000 centimeters to kilometers.
Answer:
16.5
Explanation:
Answer:
is your answer is 16.5 km
The scientist tests a prediction using a(n)
You have 50 milliliters of a 0.45 M MgBr2 solution and dilute it to a total volume of 300 milliliters. What is the molarity of the resulting solution? Describe in
words how you will find the new molarity.
Given :
Initial volume , [tex]v_1=50\ ml[/tex] .
Final volume , [tex]v_2=300 \ ml[/tex] .
Initial molarity , [tex]M_1=0.45 \ M[/tex] .
To Find :
Molarity of 300 ml solution .
Solution :
We know , for constant moles .
[tex]M_1v_1=M_2v_2\\\\M_2=\dfrac{M_1v_1}{v_2}\\\\M_2=\dfrac{50\times 0.45}{300}\ M\\\\M_2=0.075\ M[/tex]
Therefore , the molarity of the resulting solution is 0.075 M.
Hence , this is the required solution .
The electron in the He+ ion is excited to the n = 2 principal state. What is the energy of the electron now?
Answer:
= -13.6 eV
Explanation:
E = -13.6 ÷ [tex]\frac{Z^{2} }{n^{2} }[/tex]
where n is the principal state
Z is atomic number
and E is energy in electron volts.
Given that n = 2 and Helium Z = 2
⇒ E = -13.6 ÷ [tex]\frac{2^{2} }{2^{2} }[/tex]
= -13.6 eV
I believe this is helpful and easy to follow.
HELP! I WILL GIVE BRAINIEST AND 20 POINTS what is a hypothesis? give an example of a hypothesis
Answer:
By definition:
A supposition or proposed explanation made on the basis of limited evidence as a starting point for further investigation.A proposition made as a basis for reasoning, without any assumption of its truth.Example:
If I study hard in school, I will get good grades.
What volume is show in this picture?
Answer:
millileter????
What is the best use of atomic model to explain the charge of particles and Thompson's beams?
Answer:
An atom's smaller negative particles are at a distance from the central positive particles, so the negative particles are easier to remove.
Explanation:
How many molecules of carbon dioxide are created when 16 molecules of propane react in the following
unbalanced equation?
C3H3 +02— CO2+ H20
Answer:
48 molecules of CO₂
Explanation:
I think you made a mistake in your question. The formula for propane is C₃H₈, not C₃H₃. But, I will give you the answer for both cases.
For C₃H₃:
First you have to balance the equation.
4 C₃H₃ + 15 O₂ ⇒ 12 CO₂ + 6 H₂O
Next, you need to use the mole ratios between C₃H₃ and CO₂ to find the amount of molecules of CO₂ you will produce with the given amount of C₃H₃.
(16 mol's C₃H₃) × (12 mol's CO₂/4 mol's C₃H₃) = 48 mol's CO₂
You will get 48 molecules of CO₂.
For C₃H₈:
Balance the equation.
C₃H₈ + 5 O₂ ⇒ 3 CO₂ + 4 H₂O
Use the mole ratios between C₃H₈ and CO₂.
(16 mol's C₃H₈) × (3 mol's CO₂/1 mol's C₃H₈) = 48 mol's CO₂
You will get 48 molecules of CO₂ for this equation as well.
1.Calculate the frequency of a chemical shift at 1.25 ppm using a 400 MHz NMR spectrometer.A)1500 HzB)450 HzC)320 HzD)500 Hz
Answer:
D
Explanation:
Chemical shift is given as
Frequency/frequency of instrument
Let c = chemical shift
F = frequency
I = frequency of instrument
Chemical shift = frequency/frequency Instrument
1.25ppm = Frequency /400
We cross multiply to find frequency
Frequency = 400 x 1.25
Frequency = 500Hz
Option d is the answer since it is 500hz
Larissa needs to make 500ml of 2.00 M NaCl. The molecular weight of NaCl is 58.44. How does she make 500ml of 2.00 M NaCl? Question 3 options: A) Measure 29.22g NaCl and dissolve it into 500ml water. B) Measure 29.22g NaCl, dissolve it into 400ml water, and then top off to 500ml in a volumetric flask. C) Measure 58.44g NaCl and dissolve it into 500ml of water. D) Measure 58.44g NaCl, dissolve it into 400ml water, and then top off to 500ml in a volumetric flask.
Answer:
D) Measure 58.44g NaCl, dissolve it into 400ml water, and then top off to 500ml in a volumetric flask.
Explanation:
2.00M NaCl is a solution that contains 2.00 moles of NaCl per liter of solution.
As you want to prepare 500mL = 0.500L of the solution you need:
0.500L * (2.00 moles / L) = 1.00 moles of NaCl are required to prepare the solution.
Now, to convert these moles to grams you must use Molar weight (58.44g/mol) as follows:
1 moles of NaCl * (58.44g / mol) = 58.44g of NaCl are required to dissolve in 500mL to prepare the 2.00M solution.
And right option is:
D) Measure 58.44g NaCl, dissolve it into 400ml water, and then top off to 500ml in a volumetric flask.-You can't top off a solution before dissolve all solute because it is possible the volume changes-
Answer:
D) Measure 58.44g NaCl, dissolve it into 400ml water, and then top off to 500ml in a volumetric flask.
Explanation:
I got it right in class!
Hope this Helps!! :))
Which ester, when treated with NaOEt, gives this Claisen condensation product? 1. (CH_3)_2CHCH_2CO_2CH_2CH_3 2. (CH_3)_2CHCH_2CH_2CO_2CH_2CH_3 3. (CH_3)_2CHCH_2CH_2CH_2CO_2CH_2CH_3 4. CH_3CH_2CH(CH_3)CH_2CO_2CH_2CH_3
Answer:
( CH_3) _2CHCH_2CH_2CO_2CH_2CH
A reagent bottle contains a stock solution of 0.90% by mass of sodium chloride, NaCl.
The density of the solution is 1.00 g cm ?. Calculate
(i) the mole fraction of NaCl
(ii) the molality of NaCl solution
(111) the volume of the stock solution required to prepare 100 mL of 0.01 M NaCl
solution.
Answer:
I. 2.79x10⁻³
II. 0.155m
III. 6.49mL of the solution you must add from the stock solution
Explanation:
A solution of 0.90% by mass NaCl means that, in 100g of solution, you have 0.90g of NaCl. In other words, there are 0.90g of NaCl + 99.1g of water.
I. Mole fraction of NaCl is the ratio between moles of NaCl and total moles of solution.
Moles NaCl:
0.90g * (1mol / 58.44g) = 0.0154 moles NaCl
Moles water:
99.1g water * (1mol / 18.01g) = 5.50 moles water.
Total moles = 5.50 +0.0154 moles = 5.518 moles
Mole fraction NaCl: 0.0154 / 5.518 moles =
2.79x10⁻³II. Molality is the ratio between moles of solute (NaCl) and kg of solvent.
There are 99.1g of water = 0.0991kg.
Molality is: 0.0154 moles / 0.0991kg
0.155mII. 100mL of a 0.01M are:
100mL = 0.100L * (0.01 mol / L) = 1x10⁻³ moles of NaCl
In 100g = 100mL (Density of 1g/mL) there are 0.0154 moles. To have 1x10⁻³ moles you need:
1x10⁻³ moles of NaCl * (100mL / 0.0154 moles) =
6.49mL of the solution you must add from the stock solutionI. Mole fraction of NaCl is 2.79x10⁻³
II. Molarity of NaCl solution is 0.155m
III. 6.49mL of the stock solution required to prepare 100 mL of 0.01 M NaCl solution.
What does % by mass mean?
A solution of 0.90% by mass NaCl means that, in 100g of solution, you have 0.90g of NaCl.
Or
There is 0.90g of NaCl + 99.1g of water.
We need to find:
I. Mole fraction of NaCl:
Mole fraction can is the ratio of moles of Solute to the total number of moles of the solutes and the solvent.
Moles of NaCl(solute) = 0.90g * (1mol / 58.44g) = 0.0154 moles NaCl
Moles of water(solvent) = 99.1g water * (1mol / 18.01g) = 5.50 moles water.
Total moles = 5.50 +0.0154 moles = 5.518 moles
Mole fraction of NaCl = [tex]\frac{0.0154}{ 5.518} =2.79 * 10^{-3}[/tex]
II. Molality is a measure of the number of moles of solute(NaCl) in a solution corresponding to 1 kg or 1000 g of solvent
Since, 99.1g of water = 0.0991kg.
Molality of NaCl = [tex]\frac{0.0154 moles}{0.0991 kg}=0.155m[/tex]
III. 100mL of a 0.01M is:
100mL = 0.100L * (0.01 mol / L) = 1x10⁻³ moles of NaCl
In 100g = 100mL (Density of 1g/mL) there are 0.0154 moles. To have 1x10⁻³ moles you need:
1x10⁻³ moles of NaCl * [tex]\frac{100 mL}{0.0154 moles}[/tex] = 6.49mL of the solution you must add from the stock solution
Learn more:
https://brainly.com/question/15063496
14 oz (ounces) is the same as how many lbs (pounds)?
Answer:
0.875 Pounds
Explanation:
Formula is
Just divide the mass value by 16
A technician is installing a liquid cooling system for a high-end gaming PC. Which of the following liquids is MOST likely used for cooling?A. Iodine
B. Mercury
C. Thermal paste
D. Oil
Write the volume of the liquid, in milliliters, using the proper number of significant figures.Express your answer with the appropriate units.
Answer:
19.5 mL
Explanation:
A piece of metal weighing 267.0 g is placed in a graduated cylinder containing 229.0 mL of water. The volume of water now reads 257.5 mL. From these data calculate the density of the metal. e provided box. A piece of metal weighing 267.0 g is placed in a graduated cylinder containing 229.0 mL of water. The volume of water now reads 257.5 mL. From these data calculate the density of the metal.
Answer:
9.368g/mL
Explanation:
The density is defined as the mass of a compound in a determined volume.
Based on Archimedes' law, the volume of the piece of metal is the difference between the volume of the water + the inmersed piece - the original volume of water. That is:
Volume of the metal:
257.5mL - 229.0mL = 28.5mL
As the mass of the metal is 267.0g; its density is:
Density:
267.0g / 28.5mL =
9.368g/mLWhich of the following statements is not true for an exothermic reaction?a. The temp. of the surroundings increasesb. The temp of the reaction systems increasesc. The products have a higher heat content than the reactantsd. Heat passes from the reaction system to the surroundingse. The enthalpy change for the reaction is negative
Answer:
The products have a higher heat content than the reactants
Explanation:
Recall that the change in enthalpy for a reaction is obtained from
∆Hreaction= enthalpy of products - enthalpy of reactants
For an exothermic reaction, enthalpy of reactants > enthalpy of products, hence ∆Hreaction is negative.
This implies that the heat content of reactants is greater than that of products for an exothermic reaction. Hence the option selected in the answer is false as written.
if a mixture of 90 g of hydrogen sulfide and 70.5 g of chromium oxide are allowed to raeact what mass of water can be formed
Answer:
24.84 g
Explanation:
The balanced reaction equation is;
Cr2O3(s) + 3H2S(g) ⟶Cr2S3(s) + 3H2O(l)
We must first determine the limiting reactant
For chromium III oxide;
Amount of chromium III oxide = mass/molar mass = 70.5g/ 151.99 g/mol = 0.46 moles
If 1 mole of chromium III oxide yields 3 moles of water
0.46 moles of chromium III oxide yields 0.46 × 3 = 1.38 moles of water
For hydrogen sulphide
Amount of hydrogen sulphide = mass/molar mass = 90g/ 34 gmol-1 = 2.64 moles
If 3 moles of H2S yields 3 moles of water
2.64 moles of H2S yields 2.64 × 3/3 = 2.64 moles of water
Hence chromium III oxide is the limiting reactant.
Mass of water produced= 1.38 moles × 18gmol-1= 24.84 g
A statement that can be proven by observation or measurement is known as a(n):
a.
opinion
b.
value
c.
fact
d.
belief
Please select the best answer from the choices provided
A
B
C
D
The correct answer for this question is that a statement that can be proven by observation or measurement is known as a fact. The other possible answers here simply refer to idea that different individuals can place value on, but that are not necessarily known to be true.