Answer:
Chemists make observations on the macroscopic a scale that lead to conclusions about microscopic features
Explanation:
Many important chemical observations are made on the macroscopic scale. This is because, many of the scientific equipments available are not presently able to provide direct evidence about microscopic processes. Evidences obtained from macroscopic observations could serve as important insights into the nature of certain microscopic processes.
This is evident in the study of the structure of the atom. Most of the evidences that led to the deduction of the atomic structure were obtained from macroscopic evidence but ultimately provided important information about the microscopic structure of the atom.
It is true that Chemists make observations on the macroscopic scale that lead to conclusions about microscopic features.
Macroscopic observations are those that humans are able to see with their naked eyes.
Observing macroscopic phenomenon, scientists are able to come up with conclusions at a microscopic level because anything that happens at the macroscopic level is as a result of microscopic occurrences on a much smaller level.
Examples of macroscopic occurrences that lead to microscopic conclusions:
Water evaporating when heated allows scientists to conclude that atoms move faster when they gain heat Food decaying allows scientists to conclude that microscopic organisms are working on the food.In conclusion, the observations we make on a macroscopic scale allow for microscopic conclusions.
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Which of the following molecules can serve as both a hydrogen bond donor and acceptor? (Select all that apply.) a) CH30PO32. b) (CH3CH2)20 c) NH, CONHd) CH30H e) NH3
Answer:
NH3
Explanation:
A hydrogen bond donor is the supplier of the hydrogen atom that is involved in the hydrogen bonding interaction.
A hydrogen bond acceptor is the electronegative atom that 'accepts' the hydrogen in the hydrogen bond. Such electronegative atoms usually possess an unshared pair of electrons such as nitrogen.
We can see from the above definitions that NH3 is able to act in the capacity of a hydrogen bond donor(due to the presence of three N-H bonds) or as a hydrogen bond donor due to presence of an unshared pair on nitrogen atom.
Mike is about to see his slide at the high power objective lens, he wants to move the slide so he can see better. Do you think using a coarse adjustment knob will help him find his specimen on the slide. What potential danger can he face if he uses the coarse adjustment with a high power objective lens?
Answer:
Coarse and fine adjustment The coarse adjustment knob should only be used with the lowest powerobjective lens. Once it is in focus, you will only need to use the fine focus. Using the coarse focus withhigher lenses may result in crashing the lens into the slide.
i need to know the measurements of this to the appropriate amount of significant figures
Answer:
[See Below]
Explanation:
23 or 23.5 ml.
Balance the following oxidation-reduction reaction and indicate which atoms have undergone oxidation and reduction.
____Cu + ____HNO3 ----> ____Cu(NO3)2 + _____NO2 + _____H2O
You should research it on quizlet.
There are 24 g of carbon in a substance with a mass of 30 g. What is the percent carbon by mass for this substance?
here are 24 g of carbon in a substance with a mass of 30 g. What is the percent carbon by mass for this substance?
Answer:
Explanation:
The composition of the vapor in mass percent.
According to Dalton's law,
where is the partial pressure of the gas j, is the mole fraction of the gas j in the gas mixture and is the total pressure.
To know the composition of the vapor we must first calculate the molar fractions of the components of the mixture in the vapor:
→
→
If we consider 1 mole of solution then we will have 0.56 mol of benzene and 0.44 mol of toluene in the vapor. In this way, the number of grams of each component in the vapor will be,
The percentage by mass of each component in the vapor will be,
% benzene = (g benzene / g total) x 100% = (43.7 g / (43.7 g + 40.6 g)) x 100% → % benzene = 51.8 %
% toluene = 100 % - % benzene → % toluene = 41.2%
So, the composition of the vapor in mass percent is 51.8 % benzene and 41.2% toluene.
Why is the composition of the vapor different from the composition of the solution?
The composition of the vapor will be different from that of the solution, since the more volatile compound will have a larger molar fraction in the vapor phase than in the liquid phase.
In a mixture with different volatile components the compound that volatilizes more easily is the one that will have greater capacity to escape from the solution in the form of vapor and, therefore, will be in a greater composition in the vapor above the solution.
We can measure this by means of vapor pressure, which is a measure of the volatility of a substance, that is, the capacity of the substance to pass from a liquid to a gaseous state. In the question, benzene is in greater proportion than toluene in the vapor mixture since it has a higher vapor pressure (94.2 torr) than toluene (28.4 torr).
Which chemical formula represents an organic molecule? A.CCl2F2 B.4H2O C.Al2O3 D.H2SO4
Answer:
The answer is Option A = CCl2F2
The chemical formula for an organic molecule is CCl2F2. The correct option is A.
What is an organic molecule?An organic molecule is a complicated compound that is chiefly comprised of carbon atoms bonded with other elements and another carbon atoms.
All lifeforms on Earth are comprised of organic molecules. A molecule is a cluster of atoms which are basically bonded together.
Molecules other than organic molecules is referred to as inorganic molecule. These are basically simple and are not usually encountered in living things.
Although all organic substances encompasses carbon, some substances containing carbon, such as diamonds, are taken as inorganic.
Organic compounds as well as inorganic compounds develops the basis of chemistry.
The chief distinction between organic and inorganic compounds is that organic compounds always contain carbon while most inorganic compounds do not encompass carbon.
Also, perhaps all organic compounds contain carbon-hydrogen or C-H bonds.
Thus, the correct option is A.
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Using VSEPR model, how is the electron arrangement about the central atom (electron-pair geometry) for XeF4 ?
Answer:
See explanation
Explanation:
XeF4 has a square planar structure. There are six electron pairs on the valence shell of the central atom. This gives rise to an octahedral geometry based on valence shell electron pair repulsion theory.
There are two lone pairs of electrons present on the central atom, hence the four bond pairs are found to occupy the corners of a square thereby giving a square planar compound. The two lone pairs are found above and blow the plane of the square.
in a science fiction movie, a woman proceeds through nine months of pregnancy in minutes. she takes in no nutrients during this time. she dies during labor, and an emergency c-section is performed to save the child. the child lives for only a matter of hours, rapidly aging, and dies a withered old man. a classmate claims that the movie is based on a government-documented but secret alien encounter.
Answer:
Sounds great
Explanation:
Probably fake but you never know do you
What does this ruler read as ? I need some help !!
Answer: 41 7/10
Explanation: The mark is on the seventh out of ten marks
Can someone explain to me what I'm doing wrong? 68mL was wrong as well. Selecting "tenths place" for 3a and "hundredths place" for 3b and then putting a decimal was wrong as well. I'm lost as to what I should do.
Answer:
Tens place
Ones place
69.5 ml
Explanation:
Hi! Sorry about your frustration.
Looking at the attachment again, I can then say that
3a) the answer would be only tens place. You may think ones place is correct, but then again look at the beaker. Are there any measurement in ones graduated on it? The question says "certain", while it's possible to calculate in ones, you most likely would be guessing and not certain about it.
3b) from the explanation I did in 3a above, it is thus clear ones place is the answer here. Calculating in tens is very certain, calculating in tenth and hundredth place is quite hard, if not impossible. Therefore, ones place is possible, but uncertain.
3c) If both 68 & 69 are incorrect, I'd advise you try something even much closer to 70, in 69.5
Kindly vote brainliest, thanks
reaction container holds 5.77g of P4 and 5.77g of O2. The following reaction occurs:
P4 + O2 → P4O6.
If enough oxygen is available then the P4O6 reacts further:
P4O6 + O2 → P4O10. (P=31, O =16)
a. What is the limiting reagent for the formation of P4O10? (1mk)
b. What mass of P4O10 is produced? (3mks)
c. What mass of excess reactant is left in the reaction container? (1reaction container holds 5.77g of P4 and 5.77g of O2. The following reaction occurs:
P4 + O2 → P4O6.
If enough oxygen is available then the P4O6 reacts further:
P4O6 + O2 → P4O10. (P=31, O =16)
a. What is the limiting reagent for the formation of P4O10? (1mk)
b. What mass of P4O10 is produced? (3mks)
c. What mass of excess reactant is left in the reaction container? (1
Answer:
a. O₂ is limiting reactant
b. 5.68g P₄O₁₀ are produced
c. 5.83g P₄O₆ are left in the reaction container
Explanation:
Based in the first reaction,
P₄ + 3O₂ → P₄O₆
1 mole of P₄ reacts with 3 moles of oxygen
Initial moles of P₄ and O₂ are:
Moles P₄ (Molar mass: 124g/mol):
5.77g P₄ * (1mol / 124g) = 0.0465 moles P₄
Moles O₂ (32g/mol):
5.77g O₂ * (1mol / 32g) = 0.180 moles O₂
For a complete reaction of 0.0465 moles P₄ are required:
0.0465 moles P₄ * (3 moles O₂ / 1 mol P₄) = 0.140 moles of O₂
That means will remain 0.040 moles of O₂ and there are produced 0.0465 moles of P₄O₆
For the second reaction:
P₄O₆ + 2O₂ → P₄O₁₀
2 moles of oxygen reacts per mole of P₄O₆
For a complete reaction of P₄O₆ are required:
0.0465 moles P₄O₆ * (2 moles O₂ / 1mol P₄O₆) = 0.093 moles of O₂. As there are just 0.040 moles of O₂,
a. O₂ is limiting reactantb. There are produced:
0.040 moles O₂ * (1 mole P₄O₁₀ / 2 moles O₂) = 0.020 moles P₄O₁₀
In mass (Molar mass: 284g/mol):
0.020 moles * (284g / mol) =
5.68g P₄O₁₀ are producedc. Also, 0.020 moles P₄O₆ are reacting and will remain:
0.0465 mol - 0.020 mol = 0.0265 moles P₄O₆
In mass (Molar mass: 220g/mol):
0.0265 moles P₄O₆ * (220g / mol) =
5.83g P₄O₆ is left in the reaction container Hypothesis is a educated quess
True
False
Answer:
True
Explanation:
A hypothesis is an educated guess about the outcome of an experiment or thought
6. Which statement is true about all metals?
A) They are attracted to a magnet.
B) They are weak and brittle.
C) They may be used to form alloys.
D) They react with water.
Answer:
A They are attracted to a magnet
Answer:
not sure but I think it's c
Which of the following are properties of acids? Check all that apply. • A. Corrosive • B. Reacts with certain metals • C. Tastes bitter □ D. Turns litmus paper blue
Explanation:
a) Corrosive and b) Reacts with certain metals
Sodium only has one naturally occuring isotope, Na23 , with a relative atomic mass of 22.9898 u. A synthetic, radioactive isotope of sodium, Na22 , is used in positron emission tomography. Na22 has a relative atomic mass of 21.9944 u.
A 1.5909 g sample of sodium containing a mixture of Na23 and Na22 has an apparent "atomic mass" of 22.9785 u . Find the mass of Na22 contained in this sample
Answer:
0.000399316 g
Explanation:
We can start with the molar fraction for each isotope:
We can say that the abudandance of [tex]^2^3Na[/tex] is an unknow value "X" and the molar fraction of [tex]^2^2Na[/tex] is "Y". We have to keep in mind that the molar fractions can be added:
Y + X = 1
So, we can put the molar fraction of [tex]^2^2Na[/tex] in terms of [tex]^2^3Na[/tex], so:
Y=1-X
So, we will have the molar fraction of each isotope:
[tex]^2^2Na[/tex]: X-1
[tex]^2^3Na[/tex]: X
And the atomic mass:
[tex]^2^2Na[/tex]: 21.9944
[tex]^2^3Na[/tex]: 22.9898
If we multiply the molar mass by the each atomic mass of each isotope we will have:
[tex] 22.9898*(X)~+~21.9944*(X-1)~=~22.9785[/tex]
Now we can solve for "X" :
[tex]22.9898X~+~21.9944X~-21.9944~=~22.9785[/tex]
[tex]44.9842X-21.9944~=~22.9785[/tex]
[tex]44.9842X~=~22.9785~+~21.9944 [/tex]
[tex]44.9842X~=~44.9729 [/tex]
[tex]X~=~\frac{44.9729}{44.9842}[/tex]
[tex]X~=~0.999749 [/tex]
The molar fraction of [tex]^2^3Na[/tex] is 0.999749. Now we can calculate the molar fraction of [tex]^2^2Na[/tex], so:
[tex]Y~=~1-0.999749~=~0.000251 [/tex]
Now, if we multiply the molar fraction by the mass we can find the mass of [tex]^2^2Na[/tex], so:
[tex]mass~of~^2^2Na~=~1.5909~g*0.000251~=~0.000399316~ g[/tex]
The mass of [tex]^2^2Na[/tex] is 0.000399316 g
I hope it helps!
Perform the following calculation, 39 / 24.2 . The answer rounded to the correct number of significant figures is which of the following?
Answer:
Hey!
39 / 24.2 = 943.8
Explanation:
943.8 to 2 s.f (best option for rounding)
= 940
ANSWER = 940
HOPE THIS HELPS!
Which ink spot had the most pigments? Question 3 options: black red blue green Which solvent caused the ink from the dots to move the most? Question 4 options: half water, half alcohol alcohol vegetable oil water
Answer:
The water/alcohol solvent caused the dots to move the most. The oil solvent
Explanation:
what do you understand by physical change ? give example
Answer:
Physical change are the temporary reversible change in which no new substance is formed.
Example: boiling of milk, melting of wax, cooling water,etc.
What is the enthalpy change during the process in which 100.0 g of water at 50.0 C is cooled to ice at -30 oC
Answer:
33600 J
Explanation:
From the question,
ΔH = cm(t₂-t₁)..................... Equation 1
Where, ΔH = Enthalpy change of water, c = specific heat capacity of water, m = mass of water, t₂ = Final temperature of water, t₁ = Initial temperature of water
Given: c = 4200 J/kg.°C, m = 100 g = 0.1 kg, t₂ = 50°C, t₁ = -30°C
Substitute these values into equation 1
ΔH = 4200(0.1)(50+30)
ΔH = 420(80)
ΔH = 33600 J
Please show some work For the reaction: NO(g) + 1/2 O2(g) → NO2(g) ΔH°rxn is -114.14 kJ/mol. Calculate ΔH°f of gaseous nitrogen monoxide, given that ΔH°f of NO2(g) is 33.90 kJ/mol. Answers: 181.9 kJ/mol -35.64 kJ/mol 91.04 kJ/mol 148.0 kJ/mol -114.1 kJ/mol
Answer:
148.04 kJ/mol
Explanation:
Let's consider the following thermochemical equation.
NO(g) + 1/2 O₂(g) → NO₂(g) ΔH°rxn = -114.14 kJ/mol
We can find the standard enthalpy of formation (ΔH°f) of NO(g) using the following expression.
ΔH°rxn = 1 mol × ΔH°f(NO₂(g)) - 1 mol × ΔH°f(NO(g)) - 1/2 mol × ΔH°f(O₂(g))
ΔH°f(NO(g)) = 1 mol × ΔH°f(NO₂(g)) - ΔH°rxn - 1/2 mol × ΔH°f(O₂(g)) / 1 mol
ΔH°f(NO(g)) = 1 mol × 33.90 kJ/mol - (-114.14 kJ) - 1/2 mol × 0 kJ/mol / 1 mol
ΔH°f(NO(g)) = 148.04 kJ/mol
Define molecules distinguish between a molecule of an element and a molecule of a
compound.
Answer:
molecules are the groups of atom bonding together , representing the smallest fundamental unit of a chemical compound that can take part in a chemical reaction
What must happen to uranium before it can be used as a fuel source?
Answer:
Uranium must be purified before it is used as a fuel source
Explanation:
The purer the uranium sample, the more the concentration of uranium in the fuel is.
Whenever uranium is extracted from nature, it contains a lot of impurities. Only a few special nuclear reactors can utilize uranium in this raw state. most of the others have to get uranium to become about 3% pure before they begin using it.
To do this, uranium has to be passed through a series of chemical reactions all with the aim of extracting the other compounds that may be present in the fuel.
A metal object has a mass of 8.37 g. When it was placed in a graduated cylinder containing 20.0 mL of water, the water level rose to 23.1 mL. What is the density and identity of the metal?
Answer:
Explanation:
mass = 8.37 grams
volume = 23.1 - 20.0 = 3.1 mL
density = mass / volume
density = 8.37 / 3.10 = 2.70
Be sure and add the 0 in your answer. You have 3 places of significant digits.
How many dm³ of hydrogen,measured at s.t.p.,would be needed to reduce 47.7g of copper(II) oxide to copper?
A. 4.48
B. 6.72
C. 10.82
D. 13.44
help a friend please....will mark brainliest
Answer:
13.44 dm³ of hydrogen is needed for the reaction.
(D) is correct option
Explanation:
Given that,
Mass of copper(II) oxide = 47.7 g
We know that,
Molar mass of CuO = 63.5 + 16 = 79.5 g/mol
We need to calculate the number of moles in 47.7g of copper(II) oxide,
Using formula of moles
[tex]mole=\dfrac{mass}{molar\ mass}[/tex]
Put the value into the formula
[tex]moles=\dfrac{47.7}{79.5}[/tex]
[tex]moles=0.6\ mole[/tex]
Now, we write the balanced equation for the reaction
[tex]CuO+H_{2}\Rightarrow Cu+H_{2}O[/tex]
Here, one mole of CuO reacted with one mole of hydrogen to produce one mole of Cu and one mole of water.
We need to calculate the number of moles of hydrogen needed to react with 0.6 mole of copper(II) oxide
Using the balanced equation,
1 mole of CuO reacted with 1 mole of Hydrogen.
Therefore, 0.6 mole of CuO will also react with 0.6 mole of hydrogen.
We need to calculate the volume of occupied by 0.6 mole of H2 at STP
Using formula of volume
[tex]n=\dfrac{V}{V'}[/tex]
Where, n = mole of hydrogen
V = occupied volume
V'= volume at STP
Put the value into the formula
[tex]0.6=\dfrac{V}{22.4}[/tex]
[tex]V=0.6\times22.4[/tex]
[tex]V=13.44\ dm^3[/tex]
Hence, 13.44 dm³ of hydrogen is needed for the reaction.
A gas has a temperature of 273.15 K and a pressure of 101.325 kPa. What can be concluded about the gas? It has reached standard temperature and pressure. The pressure needs to be increased to reach the standard pressure. The temperature needs to be increased to reach the standard temperature. Both the temperature and pressure need to be lowered to reach STP.
Explanation:
A gas has a temperature of 273.15 K and a pressure of 101.325 kPa. It can be concluded that this gas has reached standard temperature and pressure.
Standard temperature is zero degree celcius which corresponds to 273.15 degree kelvin.
Standard pressure is 760 mmHg which corresponds to 101.325 kPa.
Answer:
a. it has reached standard temperature and pressure
Explanation:
edge 2021
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Consider a 0.5 L buffer that contains 0.12 M HOCl and 0.080 M KOCl. What is the pH of this buffer after adding 2.5 mL of 10M KOH to the solution
Answer:
pH = 7.73
Explanation:
The pKa of the HOCl/KOCl buffer is 7.46. To determine the pH of this buffer we can use H-H equation:
pH = pKa + log [A⁻] / [HA]
pH = 7.46 + log [KOCl] / [HOCl]
Where [] is molarity -or moles- of each compound
Initial moles of HClO and NaClO:
HOCl: 0.500L * (0.12mol / L) = 0.06 moles HOCl
KOCl: 0.500L * (0.080mol / L) = 0.04 moles KOCl
Now, HOCl reacts with KOH producing KOCl:
HOCl + KOH → KOCl + H₂O
The moles of KOH in the reaction are:
2.5x10⁻³L * (10mol /L) = 0.025 moles KOH
That means after the reaction, 0.025 moles of HOCl are consumed and 0.025 moles of KOCl are produced.
And after the reaction, moles are:
Final moles:
HOCl: 0.06mol - 0.025mol = 0.035 mol
KOCl: 0.04mol + 0.025mol = 0.065 mol
Replaing in H-H equation:
pH = 7.46 + log [0.065mol] / [0.035mol]
pH = 7.73During which phase of mitosis do the chomosomes align at the middle part of the cell? (1 point) O telophase O anaphase O metaphase O prophase
Answer:
Metaphase - this is when the chromosomes align
During Metaphase of mitosis, the chomosomes align at the middle part of the cell. Henc ethe correct option is (C).
What is Mitosis cell division ?In cell biology, mitosis is a part of the cell cycle in which replicated chromosomes are separated into two new nuclei.
Cell division by mitosis gives rise to genetically identical cells in which the total number of chromosomes is maintained. Therefore, mitosis is also known as equational division.
During metaphase, the nucleus dissolves and the cell's chromosomes condense and move together, aligning in the center of the dividing cell.
At this stage, the chromosomes are distinguishable when viewed through a microscope.
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0.000657
significant figures
Answer:
3 Significant Figures
Explanation:
the significant figures in 0.000657 are 6, 5, and 7.
You start with 420 mg of isotope which has half life of 20 days. How many mg will be left after 40 days
Answer:
105 mg
Explanation:
The following data were obtained from the question:
Original amount (N₀) = 420 mg
Half life (t½) =20 days
Time (t) = 40 days
Amount remaining (N) =..?
Next, we shall determine the rate constant K, for the disintegration.
This can be obtained as follow:
Half life (t½) =20 days
Rate constant (K) =?
K = 0.693/ t½
K = 0.693/20
K = 0.03465 /day
Finally, we shall determine the amount remaining after 40 days as follow:
Original amount (N₀) = 420 mg
Rate constant (K) = 0.03465 /day
Time (t) = 40 days
Amount remaining (N) =..?
Log(N₀/N) = kt/2.3
Log (420/N) = (0.03465 x 40)/2.3
Log (420/N) = 1.386/2.3
Log (420/N) = 0.6026
420/N = antilog (0.6026)
420/N = 4
Cross multiply
420 = N x 4
Divide both side by 4
N = 420/4
N = 105 mg
Therefore, the amount remaining after 40 days is 105 mg.
what word or two-word phrase best describes the shape of the phosphorus trifluoride ( pf3 ) molecule
Answer:
trigonal pyramidal
Explanation:
There are two characteristics of molecules, one is geometry and other is shape. Shape is excluding lone pair surrounding the central element and geometry is including the lone pair. Therefore, the word or two-word phrase best describes the shape of the phosphorus trifluoride ( PF[tex]_3[/tex]) molecule is trigonal pyramidal.
What is VSEPR theory?
VSEPR stands for valence shell electron pair repulsions. VSEPR theory is used to predict the shape and geometry of molecules on the basis of valence electrons pairs that are present around the central element of the molecule.
According to VSEPR theory, Lone pair lone pair repulsion is greater than bond pair bond pair repulsion. There are so many limitations of VSEPR theory. There is a repulsion between bond pair electrons and lone pairs present on the central element. The word or two-word phrase best describes the shape of the phosphorus trifluoride ( PF[tex]_3[/tex]) molecule is trigonal pyramidal.
Therefore, the word or two-word phrase best describes the shape of the phosphorus trifluoride ( PF[tex]_3[/tex]) molecule is trigonal pyramidal.
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