1) List the known and unknown quantities.
First experiment:
Reactants
Phosphorus: 7.97 g.
Bromine: excess.
Product
Phosphorus tribromide: 69.65 g.
Second experiment
Reactants
Phosphorus: 12.05 g.
Bromine: 61.68 g.
Product
Phosphorus tribromide: unknown.
2) Write and balance the chemical equation.
[tex]2P+3Br_2\rightarrow2PBr_3[/tex]3) Convert the masses.
3.1-Convert the mass of P to moles of P.
The molar mass of P is 30.97 g/mol.
[tex]mol\text{ }P=12.05\text{ }g\text{ }P*\frac{1\text{ }mol\text{ }P}{30.97\text{ }g\text{ }P}=0.38909\text{ }mol\text{ }P[/tex]3.2-Convert the mass of Br to moles of Br.
The molar mass of Br2 is 159.8080 g/mol.
[tex]mol\text{ }Br_2=61.68\text{ }g\text{ }Br_2*\frac{1\text{ }mol\text{ }Br_2}{159.8080\text{ }g\text{ }Br_2}=0.38596\text{ }mol\text{ }Br_2[/tex]4) Which is the limiting reactant?
4.1-How many moles of Br2 do we need to use all of the P?
The molar ratio between Br2 and P is 3 mol Br2: 2 mol P.
[tex]mol\text{ }Br_2=0.38909\text{ }mol\text{ }P*\frac{3\text{ }mol\text{ }Br_2}{2\text{ }mol\text{ }P}=0.583635\text{ }mol\text{ }Br_2[/tex]We need 0.583635 mol Br2 and we have 0.38596 mol Br2. We do not have enough Br2. This is the limiting reactant.
4.2-How many moles of P do we need to use all of the Br2?
The molar ratio between Br2 and P is 3 mol Br2: 2 mol P.
[tex]mol\text{ }P=0.38596\text{ }mol\text{ }Br_2*\frac{2\text{ }mol\text{ }P}{3\text{ }mol\text{ }Br_2}=0.25731\text{ }mol\text{ }P[/tex]We need 0.25731 mol P and we have 0.38909 mol P. We have enough P. This is the excess reactant.
5) Moles of phosphorus tribromide produced from the limiting reactant.
Limiting reactant: 0.38596 mol Br2.
The molar ratio between Br2 and PBr3 is 3 mol Br2: 2 mol PBr2.
[tex]mol\text{ }PBr_2=0.38596\text{ }mol\text{ }Br_2*\frac{2\text{ }mol\text{ }PBr_3}{3\text{ }mol\text{ }Br_2}=0.25731\text{ }mol\text{ }PBr_3[/tex]6) Conver the moles of Pbr3 to mass of PBr3.
The molar mass of PBr3 is 270.6858 g/mol.
[tex]g\text{ }PBr_3=0.25731\text{ }PBr_3*\frac{270.6858\text{ }g\text{ }PBr_3}{1\text{ }mol\text{ }PBr_3}=69.6502\text{ }g\text{ }PBr_3[/tex]The mass of PBr3 produced in the reaction is 69.65 g PBr3.
.
Which of the following statements is one of the postulates in Dalton’s atomic theory?1. Atoms of different elements can physically mix together.2. Atoms of one element can be changed into atoms of another element through a chemical reaction.3. All compounds are composed of multiple elements combined together.4. Atoms of one element cannot be changed into another element through a chemical reaction.
Answer:
All atoms of a specific element are identical in mass, size, and other properties. However, atoms of different element exhibit different properties and vary in mass and size. Atoms can neither be created nor destroyed. Furthermore, atoms cannot be divided into smaller particles.
A 150 g piece of iron (Cp = 25.09 J/(mol-°C)) was heated to a temperature of
47°C and then placed in contact with a 275 g piece of copper at 20°C (Cp = 25.46
J/(mol-°C)). What is the final temperature of the two pieces of metal?
Final temperature of the two pieces of metal is 32.25°C
Temprature is the degree of hotness or coldness of the object
Here given data is
Mass of iron = 150 g
Mass of copper = 275 g
Specific heat of iron = 25.09 J/mol°C
Specific heat of copper = 25.46J/mol°C
Temprature in iron = 47°C = initial temprature = T₁
Temprature in copper = 20°C = initial temprature = T₁'
So here we have to find final temprature of two pieces of metal =?
So, the formula is Q =mcΔT
Q = (150 g - 275 g) × (25.09 J/mol°C - 25.46J/mol°C) × ( 47°C-20°C )
Q = 125×0.37×27
Q = 243 J
243 J/125×0.37 = 5.25°C = change in temprature
Initial temprature = 27°C
Final temprature = ?
ΔT = T₂ - T₁
27°C = T₂ - 5.25°C
T₂ = 27°C + 5.25°C
T₂ = 32.25°C
Final temperature of the two pieces of metal is 32.25°C
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How fast does human hair typically grow?
A.
Two centimeters per month
B.
One inch per month
C.
One centimeter per month
D.
Two centimeters every year
Answer: One centimeter per month.
Explanation: Technically speaking, human hair grows about 1/2 inch a month or 6 inches a year. 1/2 inch is approx 1.27 centimeters, or in other words, one centimeter a month. Therefore, that's your answer.
Let me know if I got it right! :)
Answer:
1 centimeter per month
Explanation:
Human hair typically grows 6 inches in a year. Since there's 12 months, we can tell that hair grows 1/2 an inch per month. 1/2 an inch is about 1 cm.
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when hydrogen, H+, and chlorine,Cl- are mixed, what are they called?
When hydrogen (H+) and chlorine (Cl-) are mixed, they are called hydrochloric acid.
How hydrochloric acid is formed?Hydrochloric acid is prepared by combining the gaseous hydrogen chloride with water. Due to the corrosive nature of the acid, ceramic, glass, or tantalum apparatus is used. Hydrochloric acid is also known as muriatic acid. It is also known as an aqueous solution of hydrogen chloride. It is a colorless solution with a pungent smell. It is classified as a strong acid because of more hydrogen atoms. It is a part of the gastric acid that is present in the digestive systems of animal species such as humans. Hydrochloric acid is an important laboratory and industrial chemical.
So we can conclude that hydrochloric acid is formed when hydrogen and chlorine are mixed.
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Modern science has shown that the following postulates of Dalton’s theory were not quite right. Choose one postulate and briefly explain how it has had to be updated based on our current knowledge of nature, particularly nuclear science.
The existence of isotopy shows that the atoms of the same element are not exactly alike.
What is the Dalton atomic theory?Recall that the atom is the simplest particle of a substances that is able to take part in a chemical reaction. Note that the empirical study of the atom became much more common after the study of John Dalton that led to the Dalton Atomic Theory.
Now, one of the postulates of the theory is the atoms of the same elements are exactly alike in all respects and are different from the atoms of other elements. The existence of isotopy have shown that the atoms of the same element could be different and behave slightly differently from each other.
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What is the sum of the coefficients when the following equation is properly balanced? __Ca(OH)2 + __H3PO4 —> Ca3(PO4)2 + __H2O
The sum of coefficients when the above-mentioned equation is balanced is 12.
How to balance a chemical equation?A chemical equation is a symbolic representation of a chemical reaction where reactants are represented on the left, and products on the right.
A chemical equation is said to be balanced when the number of atoms of each element on both sides of the equation is the same.
According to this question, calcium hydroxide reacts with phosphoric acid as follows:
3Ca(OH)₂ + 2H₃PO4 → Ca₃(PO4)₂ + 6H₂O
The sum of the coefficients of the above balanced chemical equation is 3 + 2 + 1 + 6 = 12.
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What does an Arrhenius base do when it interacts with water?
Answer:
Explanation:
Here, we want to get what will happen when an Atthenius base interacts with water
By definition, an Arrhenius base increases the concentration of hydroxide ions in aqueous solutions
What this simply mean is that when an Arrhenius base comes in contact with water, the solution is expected to have an increase in the concentration of hydroxide ion. This can be measures pH wise and we expect an increase in the pH of the solution from 7
What has happened in the field of forensics in the past few decades?
A.
Very few members of the public have heard of a case dealing with forensics.
B.
The use of forensics is more popular with the public and law enforcement.
C.
Colleges have stopped offering courses and majors in forensic science.
D.
It has become completely detached from the criminal justice system.
Answer:
c
Explanation:
V atery few members of the public have heard of a case dealing with forensics. The use of forensics is more popular with the public and law enforcement. Colleges have stopped offering courses and majors in forensic science.
7.Explain the bonding in carbon tetrachloride, CCl4—specifically, explain whether it’s covalent or ionic.
• The bond that exist between the CCl4 compound ,forms a covalent bond ,, this can be illustrated in the diagram below:
• We can see that it contains four non-polar covalent bond between carbon and chloride
In the following reaction, What quantity in moles of CH₃OH are required to give off 1501 kJ of heat? 2 CH₃OH (l) + 3 O₂ (g) → 2 CO₂ (g) + 4 H₂O(g) ∆H° = -1280. kJ
Taking into account the definition of enthalpy of a chemical reaction, 2.345 moles of CH₃OH are required to give off 1501 kJ of heat
Definition of enthalpy of a chemical reactionThe enthalpy of a chemical reaction as the heat absorbed or released in a chemical reaction when chemicals are transformed into a chemical reaction at constant pressure.
The enthalpy is an extensive property, that is, it depends on the amount of matter present.
Amount of moles of CH₃OHIn this case, the balanced reaction is:
2 CH₃OH (l) + 3 O₂ (g) → 2 CO₂ (g) + 4 H₂O(g)
and the enthalpy reaction ∆H° has a value of -1280 kJ/mol.
This equation indicates that when 2 moles of CH₃OH reacts with 3 moles of O₂, 1280 kJ of heat is released.
If it is required to give off 1501 kJ of heat, you can apply the following rule of three: If 1280 kJ of heat is released by 2 moles of CH₃OH, 1501 kJ of heat is released by how many moles of CH₃OH?
amount of moles= (1501 kJ× 2 moles of CH₃OH)÷ 1280 kJ
amount of moles= 2.345 moles of CH₃OH
In summary, the amount of moles required are 2.345 moles.
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6. Initially, a sample of nitrogen gas is found in a pressure of 4.62 atm under the temperature of 27.0℃. Find the change in temperature of the gas when the pressure is increased to 5.59 atm.
Answer: ΔT = 62.98
Explanation:
This can be done using Gay Lusac's Law which states that Pressure is proportional to temperature
So, we take p1 = 4.62 atm, t1 = (27+273)°K, p2 = 5.59 atm, t2=?
now, P1/T1 = P2/T2
From here find out T2 which would be in Kelvin and then subtract 273 to convert it into celsius. Then find the difference between T1 and T2 and you should have your answer.
How many protons and neutrons are in an atom of Pm-147 ?
Promethium is the 61st element that you can find in the periodic table and the number 147 indicates the atomic mass.
Remember that the atomic number (in this case, 61) represents the number of protons, so there are 61 protons in Pm-147.
And to find the number of neutrons, we have to subtract the atomic number (61) from the atomic mass (147):
[tex]\#\text{ neutrons = 147-61 = 86.}[/tex]So, the final answer is that we have 61 protons and 86 neutrons of Pm-147.
70 grams of potassium nitrate completely dissolve in a solution at 55°C. The same amount of solute remains dissolved when the temperature of the solution drops to 45°C, until a ____ crystal is added. At this point the excess solute rapidly falls out of the solution.
Explanation:
We form a supersaturated solution. At 45 °C the solution has more potassium nitrate that can be dissolved. The recrystallization of the excess dissolved solute can be started inserting a crystal that is called seed crystal.
Answer: seed
What’s the maximum mass of calcium chloride that can form? Not a timed or graded assignment. Quick answer = amazing review :)
In order to solve this question we need to set up the properly balanced equation first:
CaCO3 + 2 HCl -> CaCl2 + H2O + CO2
Now that our reaction is properly balanced, we have to find the limiting reactant in order to find how much mass of CaCl2 will be produced
We have:
10.0 g of CaCO3, molar mass = 100.086 g/mol
15.0 g of HCl, molar mass = 36.46 g/mol
Now we need to find the number of moles of the reactants, and see if the amount available of the other reactant is the one needed to react.
CaCO3:
100.086g = 1 mol
10g = x moles
x = 0.099 moles of CaCO3
According to the molar ratio, the CaCO3 and HCl will have a relationship in which we will always need 2 times more HCl than CaCO3, therefore if we have 0.099 moles of CaCO3, we will need 0.198 moles of HCl in order to proceed with the reaction, but we don't know if that is the right amount, let's check:
HCl:
36.46g = 1 mol
15.0g = x moles
x = 0.411 moles of HCl, this means that we have an excess of HCl, since we only need 0.198 moles in order to react with CaCO3. Therefore Calcium carbonate is the limiting reactant.
Now that we know which one is the limiting reactant, we can find the mass produced of CaCl2.
Again the molar ratio is important here, but know, we will always have the same number of moles for CaCO3 and CaCl2, 1:1 will be the molar ratio, therefore if we have 0.099 moles of CaCO3, we will also have 0.099 moles of CaCl2, using its molar mass, 110.978g/mol, we can find the final mass
CaCl2:
110.978g = 1 mol
x grams = 0.099 moles
x = 11.0 grams (it is actually 10.986 grams, but I have rounded up to 11 grams)
Explain an element Magnesium would need to react with in order to attain a subscript of 3?
The chemical element which magnesium would combine with in order to attain a subscript of 3 is nitrogen which result in the formation magnesium nitride ( Mg₃N₂ )
How magnesium attains a subscript of 3Magnesium is a metallic element which belongs to group 2 and and has a valence electron of 2. This means that in an electrovalent combination, magnesium loses 2 valence electrons to nitrogen to become Mg2+ ion. To complete this bonding, nitrogen which has 5 valence electrons accepts 3 of Mg2+ ions in addition with with its two N3− ions to form magnesium nitride. When this happens, magnesium then attains a subscript of 3.
Magnesium nitride is an electovalent or ionic compound and the bond which exist in it is Ionic bond. It is used in the synthesis of ceramic substances.
So therefore, we can confirm from above that when magnesium reacts with nitrogen, it attains a subscript of 3.
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Nitrogen is the chemical element that magnesium would mix with to get a subscript of 3, leading to the production of magnesium nitride.
What are chemical elements?Chemical elements are defined as a type of atom, including the pure substance made entirely of that type, with a specific number of protons in its nucleus.
Magnesium is a metallic element with a valence electron number of 2, and it is a member of group 2. This indicates that magnesium loses two valence electrons to nitrogen in an electrovalent combination to form the Mg2+ ion. Nitrogen, which has five valence electrons, accepts three Mg2+ ions in addition to its two N3 ions to complete this bonding and create magnesium nitride. Magnesium then achieves a subscript of 3 when this occurs.
Thus, Nitrogen is the chemical element that magnesium would mix with to get a subscript of 3, leading to the production of magnesium nitride.
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During the chlorination of silicon, chlorine gas is reacted with solid silicon to form silicon tetrachloride.Si(s) + 2Cl2(g) + heat - SiC|4(g)Which will not cause the reaction to shift towards the products?A) adding a catalystB) increasing the pressureC increasing the temperatureD) increasing the concentration of CL2(g)
Let's analyze each option to find what best fit as an answer:
A - the function of a catalyst is to lower the energy of activation in a reaction, causing it to occur in a faster way. Since this question is not much about energy or kinetics, this would be the best fit, adding a catalyst or not adding it would not be too influential in the shift of the reaction.
B - Increasing the pressure in a reaction containing gases will mostly favor the side with a lower value of moles, smaller amount of moles = less pressure, so if we add more pressure, the reaction will shift towards the side of the products
C - If we treat heat as a reactant, if we add more temperature, it will shift towards the products, to counteract this increase of temperature
D - Adding reactants will favor the reaction to shift towards the products
Therefore the answer is letter A
The wavelength of green light from a traffic signal is approximately 5.2 * 10^7 m. Calculate its frequency
If the wavelength of green light from a traffic signal is approximately 5.2 ×10⁷ m , then the frequency of the light would be 5.769 × 10¹⁶ Hz .
What is Wavelength?It can be understood in terms of the distance between any two similar successive points across any wave for example wavelength can be calculated by measuring the distance between any two successive crests.
C = λν
The frequency of the green light = 3 × 10⁸ / 5.2 ×10⁷
= 5.769 × 10¹⁶ Hz
Thus , If the wavelength of green light from a traffic signal is approximately 5.2 ×10⁷ m , then the frequency of the light would be 5.769 × 10¹⁶ Hz .
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While performing the extraction experiment, you were confused between the organic layer and the aqueous one, what is the easiest way to tell which layer is which?
The easiest way to tell which layer is wich, while performing the extraction experiment is to run a little test.
The test will consist on mixing a sample of both layers in different recipients with water.
After mixing them, the recipient with a homogeneous phase will have the aqueous layer, and the other one will be the organic layer.
Answer: The layer on top.
Explanation:
Assuming you were completing an extraction experiment and had a setup similar to the one below then the organic layer will float on top of the aqueous since most non-halogenated organic solvents have a density of less than 1.
Perform the following operation and express the answer in scientific notation 6.0 x 10^3-2.310^3 Would you please help me with this problem
Subtract the numbers and write the power 10^3
The answer is 8.3x10^3
What is the pH of a 0.670 M solution of Ca(NO₂)₂ (Ka of HNO₂ is 4.5 × 10⁻⁴)?
The pH of a 0.670 M solution of Ca(NO₂)₂ is 1.76
When HNO₂ dissociates, it forms H⁺ and NO₂⁻ ions.
HNO₂ ==> H⁺ + NO₂⁻
Ka of HNO₂ = [H⁺] [NO₂⁻] / [HNO₂] = 4.5× 10⁻⁴
Let’s take x for unknown
4.5 x 10⁻⁴ = (x)(x) / 0.670
4.5 x 10⁻⁴ = x² / 0.670
x² = 3.015 x 10⁻⁴
x = 1.74 x 10⁻²
[H⁺] = 1.74 x 10⁻² M
pH is the measurement of the acidity or basicity of a compound. It ranges from 0 to 14
Therefore, the pH of a 0.670 M solution of Ca(NO₂)₂ is
pH = -log [H⁺]
pH = -log 1.74 x 10⁻²
pH = 1.76
The pH of a 0.670 M solution of Ca(NO₂)₂ is 1.76 which lies in the acidic range (0 to 7)
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1.00 mol each of CO and Cl₂ are introduce into an evacuated 1.75 L flask. At equilibrium (668 K), the total pressure of the gaseous mixture is 32.4 atm. Calculate Kp at this temperature.
CO(g) + Cl₂(g) ―> COCI₂(g)
Was a bit lengthy but I guess you do it like this?
a graduated cylinder has a mass of 50 g when empty. When 30 mL of water is added the graduated cylinder has a mass of 120 g. If a rock is added to the graduated cylinder, the water level rises to 75 mL and the total mass is now 250 g. What is the dentisy of the rock?
The density of the solid object is obtained to be 2.89 g/mL.
What is density?The density is defined as the ratio of the mass to the volume of the object. In this case, the density is to be obtained by the use of the displacement method of the solving the problem.
Mass of the empty cylinder = 50 g
Mass of water and cylinder = 120 g
Mass of water alone = 70 g
Mass of water, cylinder and the object = 250 g
Mass of the object = 250 g - 120 g = 130 g
Volume of the object = 75 mL - 30 mL = 45 mL
Density of the object = 130 g/45 mL
= 2.89 g/mL
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Reaction Data ReactantsProductsAl(NO3)3NaClNaNO3AlCl3Starting Amount in Reaction4 moles9 moles??Determine the maximum amount of NaNO3 that was produced during the experiment. Explain how you determined this amount. I've had help on this before but im still struggling.
Step 1: Write and balance the equation:
3 NaCl + Al(NO3)3 → AlCl3 + 3 NaNO3
Step 2: We need to find the limiting and excess reactant. For this, we need to look at the stoichiometric ratio between the reactants:
3 moles of NaCl reacts with 1 mole of Al(NO3)3.
Now we do a rule of 3 for both.
For 9 moles of NaCl:
3 moles of NaCl --- 1 mole of Al(NO3)3
9 moles of NaCl --- x mole of Al(NO3)3
3x = 9
x = 3 moles of Al(NO3)3
For 4 moles of Al(NO3)3:
3 moles of NaCl --- 1 mole of Al(NO3)3
x moles of NaCl --- 4 moles of Al(NO3)3
x = 12 moles of NaCl
As we can see, to react with 4 moles of Al(NO3)3 we should have 12 moles of NaCl, but we have just 9. So the NaCl is the limiting reactant and the excess reactant is Al(NO3)3.
Step 3: We need to look at the stoichiometric ratio between the limiting reactant (NaCl) and NaNO3:
3 moles of NaCl --- 3 moles of NaNO3
9 moles of NaCl --- x moles of NaNO3
x = 9 moles of NaNO3
Answer: The maximum amount of NaNO3 that was produced during the experiment is 9 moles.
7. A given sample of gas is held in a container with the volume of 6.02 L with a temperature of 59.5℃ at a pressure of 1.20 atm. What is the final pressure when the sample of gas is administered to a new volume of 10.0 L at 20.2℃?
The final pressure of the gas when the sample gas is administered to a new volume of 10.0 L at 20.2℃ would be 0.245 atm.
Combined gas lawThe problem here has to do with the combined gas law. The law is mathematically expressed as:
[tex]p_1v_1/t_1[/tex] =[tex]p_2v_2/t_2[/tex]
Where [tex]p_1[/tex] = initial pressure, [tex]v_1[/tex] = initial volume, [tex]t_1[/tex] = initial temperature, [tex]p_2[/tex] = final pressure, [tex]v_2[/tex] = final volume, and [tex]t_2[/tex] = final temperature.
In this case,
[tex]p_1[/tex]= 1.20 atm[tex]v_1[/tex] = 6.02 L[tex]t_1[/tex] = 59.5℃[tex]v_2[/tex] = 10.0 L[tex]t_2[/tex] = 20.2℃Rearranging the combined gas equation:
[tex]p_2[/tex] = [tex]p_1v_1t_2/t_1v_2[/tex]
Substituting the different variables:
[tex]p_2[/tex] = 1.2 x 6.02 x 20.2/59.5 x 10.0
= 145.9248/595
= 0.245 atm
Thus, the final pressure of the sample gas will be 0.245 atm.
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Consider the hypothetical thermochemical equation 3 A + B → 2 C for which ΔH = 65.5 kJ/mol.What would ∆H, in kJ/mol, be for the reaction 2 C → 3 A + B?
Given the hypothetical thermochemical equation, expressed as:
[tex]3A+B\rightarrow2C;\triangle H=65.5\text{kJ/mol}[/tex]We are to find the enthalpy change (ΔH ) for the reaction 2C → 3 A + B.
• You can see that the, given reaction, 2C → 3 A + B is the, reverse ,of the thermochemical equation 3 A + B → 2 C.
• Since the ,reverse reaction is possible,, the reaction enthalpy has the ,same numerical value, but with the, ,opposite sign
Therefore, the enthalpy change ∆H, in kJ/mol, be for the reaction 2 C → 3 A + B is -65.5kJ/mol
If a gas has a pressure of 6 atm , a temp of 53k and a volume of 78 liters but the temp changes to 17k and the pressure changes to 85 atm what is the new volume
answer and explanation
we are given initial values of temperature, pressure and volume as well as the final value of temperature and pressure and we are asked to find the final volume.
we can do this using the combined gas equation
P1V1/T1 = P2V2/T2
when we plug in the values we get:
(6atm x78L)/53K = (85atm x V2/17K
8.83 = 85atm x V2 / 17K
V2 = 1.77 Liters
A student has a sample of 1.31 moles of fluorine gas that is contained in a 24.6 L container at 336 K. What is the pressure of the sample? The ideal gas constant is 0.0821 L*atm/mol*K. Round your answer to the nearest 0.01 and include units.
Answer
The pressure of the sample is 1.47 atm
Explanation
Given:
Moles, n = 1.31 mol
Volume, V = 24.6 L
Temperature, T = 336 K
The ideal gas constant, R = 0.0821 L*atm/mol*K
What to find:
Pressure, P of the sample.
Step-by-step solution:
Pressure, P of the sample can be calculated using the ideal gas equation.
[tex]\begin{gathered} PV=nRT \\ \\ \Rightarrow P=\frac{nRT}{V} \end{gathered}[/tex]Put the values of the parameters into the formula, we have;
[tex]P=\frac{1.31mol\times0.0821\text{ }L.atm/mol.K\times336K}{24.6\text{ }L}=1.47\text{ }atm[/tex]The pressure of the sample is 1.47 atm
A chemist prepares a solution of magnesium fluoride (MgF2) by measuring out 6.73mg of magnesium fluoride into a 250.mL volumetric flask and filling the flask to the mark with water. Calculate the concentration in mol/L of the chemist's magnesium fluoride solution. Round your answer to 3 significant digits.
We have to find the molarity of a solution of Magnesium Fluoride. The definition of molarity is:
Molarity = moles of solute/Volume of solution in L
Our solute is MgF₂:
Molarity = moles of MgF₂ / L of solution
From the problem we know that the volume of the solution that the chemist prepared is 250. mL, we will have to convert that into L.
We know that there are 1000 mL in 1 L. So:
1 L = 1000 mL
250. mL = 250. mL * 1 L/1000 mL = 0.250 L
Volume of solution in L = 0.250 L
Now we have to find the number of moles of MgF₂ that the chemist added. From the problem we know the mass of MgF₂ added. Let's convert it to g:
1000 mg = 1 g
mass of MgF₂ = 6-73 mg
6.73 mg = 6.73 mg * 1 g/1000 mg = 0.00673 g
mass of MgF₂ = 0.00673 g
When we want to find the number of moles that we ave in a certain amount of a compound, we have to use the molar mass. Let's find the molar mass of MgF₂.
According to the periodic table the atomic mass of Mg is 24.3 amu and the atomic mass of F is 19 amu. So the molar mass of MgF₂ is:
molar mass of MgF₂ = 24.3 + 2 * 19 = 62.3 g/mol
molar mass of MgF₂ = 62.3 g/mol
Using the molar mass we can find the number of moles that we have in 6.73 mg or 0.00673 g of MgF₂:
moles of MgF₂ = 0.00673 g/(62.3 g/mol)
moles of MgF₂ = 1.08 * 10^-4 moles
So the chemist added 1.08 * 10^-4 moles of MgF₂ in 0.250 L of solution. Then the molarity of the solution is:
Molarity = moles of solute/Volume of solution in L
Molarity = 1.08 * 10^-4 moles/0.250 L
Molarity = 4.32 * 10^-4 M
So the answer to our problem is 4.32 * 10^-4 M
how many moles in 518 grams of CaCO3
Answer:
[tex]5.18\text{ moles}[/tex]Explanation:
Here, we want to get the number of moles in the given mass
Mathematically:
[tex]Number\text{ of moles = }\frac{mass}{molar\text{ mass}}[/tex]The molar mass of CaCO3 is 100 g/mol
The number of moles is thus:
[tex]Number\text{ of moles = }\frac{518}{100}\text{ = 5.18 moles}[/tex]When working with electric charges, what symbol is used in equations torepresent the electric force on an object?A. rB. qC. FeD. E
A. r: distance
B. q: charge
C. Fe: electric force
D. E: Electric field
So the answer is option C.