Answer:
Amount of required rations ≥ 15 g
Other assumptions made:
1. All the energy released from the rations is converted to heat
2. All the rations is completely metabolized to release energy
3. No other heat losses occur in the body except due to wetness of her clothing.
Explanation:
Using H = mcθ
where m is mass of the hiker in Kg,
c is specific heat capacity of water/hiker = 4200 JKg⁻¹K⁻¹
θ is temperature change in K
Note : heat capacity of water = specific heat capacity x molar mass
specific heat capacity = heat capacity / molar mass
c = 75.348 JK⁻¹mol⁻¹/18 x 10⁻³ Kgmol⁻¹ = 4186 JKg⁻¹K⁻¹ ≅ 4200 JKg⁻¹K⁻¹
Heat lost, H = 50.0 Kg x 4200 JKg⁻¹K⁻¹ x 2.5 K
H = 5.25 x 10⁵ J = 525 KJ
To avoid this heat loss, the hiker must consume enough emergency rations that releases heat equal to or greater than the heat loss due to wetness of her clothing.
Energy per gram of rations = 35 KJ
Amount of required rations ≥ 525 KJ / 35 KJ/g
Amount of required rations ≥ 15 g
Therefore, the hiker must consume 15 g or more of her emergency rations.
Other assumptions made:
1. All the energy released from the rations is converted to heat
2. All the rations is completely metabolized to release energy
3. No other heat losses occur in the body except due to wetness of her clothing.
what is the percent composition by mass of benzene?
Answer:
25.0%
A solution of benzene (C6H6) and toluene (C7H8) is 25.0% benzene by mass. At 25 °C the vapor pressures of pure benzene and pure toluene are 94.2 torr and 28.4 torr, respectively.
Which molecule listed below is a nonpolar molecule?
(a) SO3
(b) PF5
(c) CCl4
(d) All of them.
(e) None of them.
What are 4 classes of amino acid r groups?
Answer:
non polar and neutral polar and neutral acidic and polar basic and polar
Match each phase of the scientific method with the statement that describes it.
In the space provided, write the letter corresponding to the correct phase.
ILL GIVE YOU BRAINLIST !!!!
In condensation reactions, the atoms th make up a water from what?
Answer:
This question is incomplete and it lacks options. The complete question is as follows;
In condensation reactions, the atoms that make up a water molecule are from what?
a. oxygen
b. only one of the reactants
c. both of the reactants
d. carbohydrates
e. enzymes
The answer is C. Both of the reactant
Explanation:
In a chemical reaction, two small molecules called monomers combine to form a much larger molecule called polymer in a process called CONDENSATION REACTION. Some condensation reactions is characterized by the release of a water molecule (dehydration).
This water molecule is formed as a result of the active participation of both reactants. During the reaction, hydroxyll group (-OH) from one of the reactants breaks off and combines with hydrogen ion (H+) from the other reactant to form water molecule (H2O).
Hence, the atoms that make up the water molecule come from both of the reactants participating in the condensation reaction.
Illustrate an atom and a Molecules?
Answer:
Atom is the smallest particle of pure sustance which can take part in a chemical reaction.A chrged atom is called an ion.
A molecule of an element or compound is the smallest particle of it that is stable and capable of independent existence. The molecules of element and compound are different.
Astatine is a halogen with several isotopes that all have short half-lives. Which of the following combinations of mass number and neutrons are possible as isotopes of astatine?
Answer:
A-210, n-125
A-207, n-122
A-209, n-124
Explanation:
The mass number is the sum of the number of protons and neutrons in the nucleus of an atom.
Astatine has an atomic number of 85, this is the number of protons in its nucleus. We must subtract the given number of neutrons in each option from the mass number and consider the difference. If the difference between the mass number and number of neutrons is exactly 85, then that option represents one of the isotopes of astatine.
HURRY PLEASE HELP
5 x 10^4 ÷ 2.5 x 10^2 =
Answer:
1600
Explanation:
5×10^4÷2.5×10^2
(5×10^4)
(10^4)
(5×40)
(200)
(200÷2.5)
(80)
(80×10^2)
(10^2)
(20)
(80×20)
Answer is 1600.
Sorry if it's not correct.
A solution contains 3.95 g of carbon disulfide (CS2, molar mass = 76.13 g/mol) and 2.43 g of acetone ((CH3)2CO, molar mass = 58.08 g/mol). The vapor pressure of pure carbon disulfide and acetone at 35 o C are 515 torr and 332 torr, respectively. Assuming ideal solution behavior, calculate the vapor pressure of each of the components and the total vapor pressure above the solution. The total vapor pressure above the solution at 35 o C was experimentally determined to be 645 torr. Is the solution ideal? If not, indicate whether the solution deviates from Raoult’s law in a positive or negative manner
Answer:
The solution is not ideal and shows a positive deviation from Raoult’s law since Psolution (experimental) > Psolution (actual).
Explanation:
Number of moles of CS2 = 3.95g/76.13gmol-1 = 0.0519 moles
Number of moles of acetone = 2.43g/58.08gmol-1 = 0.0418 moles
Total number of moles = 0.0937 moles
Mole fraction of CS2 = 0.0519/0.0937 = 0.5538
Mole fraction of acetone = 0.0418/0.0937 = 0.4461
From Raoult’s law;
PCS2 = 0.5538 × 515 torr = 285.207 torr
Pacetone = 0.4461 × 332 torr = 148.1052 torr
Total pressure = 285.207 torr + 148.1052 torr = 433.3 torr
What is meant by the term enthalpy of formation?
Answer:
Explanation:
There is no way to measure the absolute value of the enthalpy of a substance. Only values relative to an arbitrary reference can be determined.
The reference point for all enthalpy expressions is called the standard enthalpy of formation (ΔHºf). Substances are said to be in the standard state at 1 atm, hence the term “standard enthalpy.” The superscript “°” represents standard-state conditions (1 atm), and the subscript “f” stands for formation. By convention, the standard enthalpy of formation of any element in its most stable form is zero.
For instance, molecular oxygen (O₂) is more stable than the other allotropic form of oxygen, ozone (O₃), at 1 atm and 25°C. Thus, we can write ΔHºf (O₂) 5 0, but ΔHºf (O₃) 5 142.2 kJ/mol.
Based on this reference for elements, we can define the standard enthalpy of formation of a compound as the heat change that results when 1 mole of the compound is formed from its elements at a pressure of 1 atm.
Answer:
This is the enthalpy change that occurs when a compound is formed from its component elements.
Explanation:
This is the enthalpy change that occurs when a compound is formed from its component elements.
The fire extinguisher is the best piece of safety equipment to put out a fire on your
clothing
O True
O False
What mass of nitrogen is needed to fill an 855 L tank at STP?
Answer:
It takes 1,068.76 grams of nitrogen to fill an 855 L tank at STP.
Explanation:
The STP conditions refer to the standard temperature and pressure. Pressure values at 1 atmosphere and temperature at 0 ° C or 273.15 °K are used and are reference values for gases.
On the other side, the pressure, P, the temperature, T, and the volume, V, of an ideal gas, are related by a simple formula called the ideal gas law:
P*V = n*R*T
where P is the gas pressure, V is the volume that occupies, T is its temperature, R is the ideal gas constant, and n is the number of moles of the gas.
So, in this case:
P= 1 atmV= 855 Ln= ?R= 0.082 [tex]\frac{atm*L}{mol*K}[/tex]T= 273.15 KReplacing:
1 atm* 855 L= n* 0.082 [tex]\frac{atm*L}{mol*K}[/tex] * 273.15 K
Solving:
[tex]n=\frac{1 atm* 855 L}{0.082\frac{atm*L}{mol*K} *273.15 K }[/tex]
n= 38.17 moles
Being the molar mass of nitrogen N2 equal to 28 g / mol, you can apply the following rule of three: if there are 28 grams in 1 mole, how much mass is there in 38.17 moles?
[tex]mass=\frac{38.17 moles*28 grams}{1 mole}[/tex]
mass= 1,068.76 grams
It takes 1,068.76 grams of nitrogen to fill an 855 L tank at STP.
The number of ______ in a mass spectrum indicates the number of isotopes of an element
A.Peaks
B.Signals
C.Lighter Ions
D.Heavier Ions
Answer:
the answer is A
Which metal most likely conducts electricity best aluminum or copper
Answer: Copper
Explanation: did it on Edgenuity 2020
Answer:
first is copper
second is gold
what is true that if at the same temperature 2 objects have equal masses, but different densities
Answer:
The two objects have different volumes.
Explanation:
The density of an object measures how closely packed the mass in the object is. Density of an object is obtained by taking the ratio of the mass of an object and its volume.
Density = mass/volume
The mass present in an object is constant, but the volume may vary with temperature. The volume of substances generally increases with temperature, therefore, density decreases with increase in volume.
Two objects at the same temperature having equal masses may or may not have the same density depending on the volume each object occupy.
If two substances are at the same temperature and have equal masses but different densities, then they must have different volumes.
Write an equation that shows the formation of a sodium ion from a neutral sodium atom.
Answer:
The answer to your question is given below.
Explanation:
Sodium (Na) is a group 1 element because it has 1 electron in it's outermost shell.
Sodium ion (Na+) is formed when sodium atom (Na) lose it's outermost electron to attain the octet configuration of the noble gas element.
This can further be seen from the equation given below:
Na —> Na+ + e
Thus, we can represent the above in electronic configuration form as follow:
Na (11) => 1s² 2s²2p⁶ 3s¹
Na+ (10) => 1s² 2s²2p⁶
What are the 3 main lines of evidence for evolution?
The three main lines of evidence for revolution is Darwin used multiple lines of evidence to support his theory of evolution by natural selection -- fossil evidence, biogeographical evidence, and anatomical evidence.
The three main lines of evidence for evolution is fossil evidence, biogeographical evidence and anatomical evidence.
What is evolution?In biology evolution is a process in which change in the characterisitics of any species over a several generation on the basis of natural selection method.
The three main lines of evidence for evolution are:
Fossil evidenceBiogeographical evidenceAnatonical evidenceSo, three lines of evidences are fossil evidence, biogeographical evidence and anatomical evidence.
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Which one of these statements about strong acids is true?
A) All strong acids have H toms bonded to electronegative oxygen atoms. Strong acids are 100% ionized in water.
C) The conjugate base of a strong acid itself a strong base
D) Strong acids are very concentrated acids.
E) Strong acids produce solutions with a higher pH than weak acids.
Answer:
Strong acids are 100% ionized in water.
Explanation:
A strong acid is any acid that is completely ionized in water (achieves 100% ionization). Weak acids do not ionize completely in water. Many weak acids ionize to a very small extent in pure water.
Examples of strong acids are HCl, H2SO4, HNO3, etc.
A sample of chloroform is found to contain 12.0 g of carbon, 106.4 g of chlorine, and 1.01 g of hydrogen. If a second sample of chloroform is found to contain 28.9 g of carbon, what is the total mass of chloroform in the second sample?
Mass = _________ g chloroform
Answer:
287.6g CHCl₃
Explanation:
We can determine the structure of Chloroform, dividing the mass of each element in its molar mass:
C = 12.0g * (1mol /12g) = 1 mol C
H = 1.01g * (1mol / 1.01g) = 1 mol H
Cl = 106.4g * (1mol / 35.45g) = 3 moles Cl
The structure is CHCl₃. And its molar mass is: 12.0g C +1.01g H + 106.4g Cl = 119.41g/mol
Now, the moles of carbon in the second sample = Moles of chloroform are:
28.9g C * (1mol / 12g) = 2.408 moles C = Moles CHCl₃
And its mass is:
2.408 moles CHCl₃ * (119.41g/mol) =
287.6g CHCl₃A chemist must prepare of hydrobromic acid solution with a pH of at . He will do this in three steps: Fill a volumetric flask about halfway with distilled water. Measure out a small volume of concentrated () stock hydrobromic acid solution and add it to the flask. Fill the flask to the mark with distilled water. Calculate the volume of concentrated hydrobromic acid that the chemist must measure out in the second step. Round your answer to significant digits.
Hello. This question is incomplete. The full question is:
A chemist must prepare 500.0mL of hydrobromic acid solution with a pH of 0.50 at 25°C. He will do this in three steps: Fill a 500.0mL volumetric flask about halfway with distilled water. Measure out a small volume of concentrated (5.0M) stock hydrobromic acid solution and add it to the flask. Fill the flask to the mark with distilled water. Calculate the volume of concentrated hydrobromic acid that the chemist must measure out in the second step. Round your answer to significant digits.
Answer:
31.62 mL
Explanation:
To achieve this result, you must start by calculating the H + concentration. You will do this using the following formula:
pH = -log [H +]
0.50 = -log [H +]
[H +] = 10 ^ -0.50
[H +] = 0.31623 mol / L
After that you must consider that hydrobromic acid will have a weak capacity to disassociate, since it has a strong nature. In this case, we can consider that [HBr] = [H +] = 0.31623 mol / L.
After reaching this reason, it is necessary that you dilute the stock solution, using the formula:
C1V1 = C2V2
5.0 * V1 = 0.31623 * 500.0
V1 = 31.62 mL
And so you finish the answer.
Answer the questions for the titration of 50.0 mL of 0.05 M NH3 (Ks = 1.8x10-5) with 0.10 M HBr. A) Calculate the pH after the addition of 10 mL of HBr? B) What volume of HBr is required to reach the equivalence point? C) Calculate the pH at the equivalence point. D) Determine the pH at the midpoint.
Answer:
a) pH = 9.44
b) 25mL of HBr are required.
c) pH = 5.37
d) pH = 9.26
Explanation:
The equilibrium of NH₃ in water occurs as follows:
NH₃(aq) + H₂O(l) ⇄ NH₄⁺(aq) + OH⁻(aq)
Kb = 1.8x10⁻⁵ = [NH₄⁺] [OH⁻] / [NH₃]
The reaction of NH₃ with HBr is:
NH₃ + HBr ⇄ NH₄⁺ + Br⁻
That means when you add X moles of HBr before to reach the equivalence point, the moles are:
Moles NH₃ = Initial moles - moles HBr
Moles NH₄⁺ = Moles HBr
Initial moles NH₃ = 0.050L * (0.05mol / L) = 2.5x10⁻³ moles NH₃
Moles HBr = 0.010L * (0.10mol / L) = 1x10⁻³ moles HBr
Thus, after the reaction:
Moles NH₃ = 1.5x10⁻³moles
Moles NH₄⁺ = 1x10⁻³ moles
Using Henderson-Hasselbalch equation, pH of this solution is:
pOH = pKb + log [NH₄⁺] / [NH₃]
Where pKb is -log Kb = 4.74
And [] could be taken as moles of each compound:
pOH = 4.74 + log [1x10⁻³ moles] / [1.5x10⁻³ moles]
pOH = 4.56
And pH = 14 - 4.56
pH = 9.44b) To reach equivalence point, we need to add 2.5x10⁻³ moles HBr:
2.5x10⁻³ moles HBr * (1L / 0.10mol) = 0.025L = 25mL of HBr are required
c)At equivalence point, you will have just 2.5x10⁻³ moles of NH₄⁺ in 50.0mL + 25mL = 75mL. The molar mass of NH₄⁺ is:
[NH₄⁺] = 2.5x10⁻³mol / 0.075L = 0.0333M
The equilibrium of NH₄⁺ is:
NH₄⁺ ⇄ NH₃ + H⁺
Ka = [NH₃] [H⁺] / [NH₄⁺] = 5.556x10⁻¹⁰
[NH₃] = [H⁺] because both comes from the same equilibrium and [NH₄⁺] = 0.0333M:
[X] [X] / [0.0333M] = 5.556x10⁻¹⁰
[X]² = 1.85x10⁻¹¹M
[X] = [H⁺] = 4.3x10⁻¹¹M
pH = -log [H⁺] = 5.37
d) At midpoint, [NH₃] = [NH₄⁺]. Using H-H equation:
pOH = 4.74 + log [NH₃] / [NH₄⁺]
pOH = 4.74
And pH = 14 - 4.74
pH = 9.26Considering the temperature vs. time graph below, how does the temperature at the beginning of a change of state
compare with the temperature at the end of the change?
Temperature vs. Time
5
14
Temperature (°C)
140
120
100
80
80
40
20
Time (min)
The temperature is always lower.
The temperature is always the same.
The temperature is usually lower.
O The temperature is usually higher.
Mark this and retum
Next
Submit
Answer:
The temperature is always lower.
Explanation:
The temperature is always lower at the end of the state as compared to beginning of the state. We can see in the given data, the temperature is higher at the beginning i. e. 140 degree Celsius but with the passage of time, the temperature of a state decreases constantly and the temperature at the end is lower i. e. 20 degree Celsius. So we can conclude that the temperature is always lower.
We want to study how the temperature behaves in a change of phase. Ideally, we would read a graph and use the given information, but we can't see the graph, so for the answer, I will use a general thermodynamics knowledge instead of the missing graph.
We will see that the correct option is: The temperature is always the same
---------------------------------------
Let's start by explaining how temperature manifests in objects.
Assume we have something in solid phase. As we increase the temperature, the particles on the solid increase their kinetic energy, thus, the particles move more.
This causes that the volume of the object increases (for example when we heat up a metal and it dilates). This keeps happening until we reach a critical point, when we are near a change of phase.
At this point the energy given is not used to increase the temperature of the object, but is used to "break" bonds in such a way that the particles are more free than before. When all these bonds are "broken" the change of phase is completed, and in the case of the solid, we go from solid phase to liquid phase.
An example of this is that we can have liquid water and solid water both at 0°C, so if you have a thermometer in your home, an experiment that you can do is:
Put water in the refrigerator.
Note when the liquid water reaches 0°C
As the water starts to solidify, keep recording its temperature, you will see that it does not change (a lot, it may change a little bit) until all the water changes of phase.
So to answer this;
how does the temperature at the beginning of a change of state compare with the temperature at the end of the change?
The temperature is always the same
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How do strong southerly winds affect the vapor pressure?
Answer:
An increase
Explanation:
The strong southerly winds affect the vapor pressure by increasing it .
When the vapor pressure increases it means an increase in temperature and more evaporation occurs.
A decrease in the vapor pressure means a reduction in temperature with less amount of evaporation being involved
Do you know the three core principles of cell theory?
All living organisms are composed of one or more cells. The cell is the basic unit of structure and organization in organisms. Cells arise from pre-existing cells.
The step of scientific method that would come after testing is?
Answer:
analyze
Explanation:
After testing is analyzing your data then you compare your data to your hypothesis to see if they match
(100 POINTS AND BRAINLYEST)
Sea level is the height of the ocean’s surface. Why do sea level change?
Question 4 options:
sea level changes due to many different geological events and can rise or fall over time.
sea level changes because aquatic populations rise and fall displacing the water,
sea level changes because of El Nino’
sea level changes because the earth’s magnetic field fluctuates
Answer:
B
Explanation:
Sea level changes due to many different geological events and can rise or fall over time .
What are the causes of change in sea level change ?Sea level changes due to global warming , the water being added to the seas as the glaciers melts due to global warming and the expansion of water when it warms.
The sea level also increases due to land processes like soil erosion ,oil and ground water pumping.Changes in land water storage like dams ,changes in global precipitation patterns also make a significant contribution to change in sea level.
The increased emission of green house gases is a dominant cause for change in sea level.Fifty percent of sea level rise is due to thermal expansion of seas and the rest is due to the geological activities.
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The boiling points of some of the unknown will be difficult to measure using the procedure described. identify the liquids that will pose a problem and explain why?
Answer:
Methyl Alcohol.
Acetate
Heptane
Dioxane
Explanation:
The boiling point of liquids are measure by observing the gas pressure or vapors temperature. There are few liquids whose boiling point is difficult to measure. The gas pressure differs for every liquid. It is important to observe the vapor pressure also to identify the boiling point. The most difficult boiling point identification is for Methyl alcohol as it has ability to absorb different level of pressure.
The liquids are Methyl Alcohol, Acetate, Heptane,Dioxane
Information regarding the liquids:
The boiling point of liquids should be determined by watching the gas pressure or vapors temperature. There are few liquids whose boiling point is difficult to calculate. The gas pressure should be different for every liquid. The most difficult boiling point identification is for Methyl alcohol because it has ability to absorb different level of pressure.Find out more information about the pressure here: https://brainly.com/question/356585?referrer=searchResults
Draw the conjugate acid of ethanol
Answer:
H₃O⁺.
Explanation:
Hello,
In this case, ionization of ethanol yields hydrogen cations and ethoxide anions as follows:
[tex]CH_3COOH+H_2O\rightleftharpoons H_3O^++CH_3COO^-[/tex]
Which is at equilibrium as ethanol is a weak acid. Thus, since the conjugate acid is formed by the outgoing H⁺ and the water, we say that the conjugate acid is then the hydroxonium ion, H₃O⁺ whereas the conjugate base is the remaining anion CH₃COO⁻.
Best regards.
Bromine has two isotopes, Br79 and Br81. The isotopes occur in a 50:50 (1:1) ratio. Given that the mass spectrum of bromine contains peaks for both bromine atoms and diatomic bromine molecules, predict the number of peaks in the spectrum. What would be the relative height of the atomic peaks
Answer:
There will be 3 peaks.
Relative height of the atomic peaks would be; 158, 160 and 162
Explanation:
We are told that Bromine has two isotopes namely 79Br and 81Br in a 1 : 1 ratio (50 : 50).
This means that a compound which contains 1 bromine atom will have two peaks in the molecular ion region but it depends on which bromine isotope is contained in the molecular ion.
Thus;
Relative height of atomic peaks is given by;
m/z = 79Br¯ 79Br+ = 158
79Br¯ 81Br+ = 160
81Br¯ 81Br+ = 162
Ok, so I'm learning about mass and volume and density.
I'm confused about this research card I'm doing.
Alright, if the mass is greater than the volume the object should sink in the liquid. right?
Object 9- mass=99.0 Volume=44.0 and it sinks. Density=.222
please someone explain why it sunk when the volume is greater than the mass.
(for comparison purposes).
Object 10- Mass 42.0 Volume 461.0 and it floats. density is .090
please help me .-.
Answer:
I believe it's because density is how dense something is. So even if the volume(how much space it takes up in an object) is greater, if the densitity of the object is greater then the density of the water it will sink.
Explanation:
