Answer:
The answer is 0.342 cm³Explanation:
The volume of a substance when given the density and mass can be found by using the formula
[tex]volume = \frac{mass}{density} \\[/tex]
From the question
mass = 4.62 g
density = 13.5 g/cm³
We have
[tex]volume = \frac{4.62}{13.5} \\ = 0.3422222...[/tex]
We have the final answer as
0.342 cm³Hope this helps you
match the number of negative charges to the number of positive charges to make each combination balanced (see image for answer) just say like thanks, or a fun fact or something for ten points in the answers lol
Answer : The correct match is:
1 positive charge = 1 negative charge
2 positive charges = 2 negative charges
3 positive charges = 3 negative charges
Explanation :
As we now that there are three subatomic particles which are protons, electrons and neutrons.
The protons and neutrons are located inside the nucleus and electrons are located around the nucleus.
The protons are positively charged, the electrons are negatively charged and neutrons are neutral.
As we know that all the things are made up of charges and opposite charges attract to each other.
In a neutral atom, the positive charges and negative charges are balanced in an object. That means, in neutral atom the number of positive charges are equal to the negative charges.
So we can say that:
1 positive charge = 1 negative charge
2 positive charges = 2 negative charges
3 positive charges = 3 negative charges
Answer:
1 positive---- 1 negative
2 positive---- 2 negative
3 positive---- 3 negative
Explanation:
edge 2023
help me please loves
Answer:
K and ba
Explanation:
Answer: K and Ba
Explanation:
1. Which statement describes a compound?
A. It contains a solute.
B. Its composition can vary.
C. Its combination of atoms never changes.
D. Its components keep separate properties.
2. Which item is NOT a type of matter?
A. force
B. mixture
C. element
D. compound
3. Which combination can be used to classify all the matter on Earth?
A. forces and energy
B. atoms and elements
C. solvents and solutes
D. substances and mixtures
Which of these four elements is the most reactive metal?
Answer:
Rubidium
Answer: Rubidium is the most reactive metal. Explanation: Metals are the elements that looses electrons and thus, their chemical reactivity will be the tendency to loose electrons.
Explanation:
what is functional group of ethers?
Answer:
Explanation:The ether functional group consists of an oxygen atom that forms single bonds with two carbon atoms
The normal boiling point of benzene is 80.1°C. What is its enthalpy of vaporization if the vapor pressure at 26.1°C is 100 torr?
The heat of vaporization of benzene is required.
The heat of vaporization of benzene is 33009 J/kg.
[tex]T_0[/tex] = Normal boiling point = 80.1+273.15 K
[tex]T_B[/tex] = Boiling point at given pressure = 26.1+273.15 K
[tex]R[/tex] = Gas constant = 8.314 J/mol K
[tex]P[/tex] = Pressure at given [tex]T_B[/tex] = 100 torr
[tex]\Delta H[/tex] = Heat of vaporization
From the Clausius–Clapeyron equation
[tex]\dfrac{1}{T_B}=\dfrac{1}{T_0}-\dfrac{R\ln(\dfrac{P}{P_0})}{\Delta H}\\\Rightarrow \Delta H=\dfrac{R\ln\dfrac{P}{P_0}}{\dfrac{1}{T_0}-\dfrac{1}{T_B}}\\\Rightarrow \Delta H=\dfrac{8.314\times \ln\left(\frac{100}{760}\right)}{\frac{1}{80.1+273.15}-\frac{1}{26.1+273.15}}\\\Rightarrow \Delta H=33008.99\ \text{J/kg}[/tex]
The heat of vaporization of benzene is 33009 J/kg.
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Which of the following is an Elementary compound?
A. CO2
B. N2
C. SO2
D. H2S
heeeeeeeeeelp please please please
Answer:
Explanation:
In my opinion the answer should be SO2
Answer:
a should be answer i think.
Calculate the pH of a solution containing a caffeine concentration of 455 mg/L . Express your answer to one decimal place.
Answer:
Explanation:
Caffeine is a weak base with pKb = 10.4
Kb = 10⁻¹⁰°⁴ = 3.98 x 10⁻¹¹
molecular weight of caffeine = 194.2
455 x 10⁻³ g / L = 455 x 10⁻³ / 194.2 moles / L
concentration of given solution a = 2.343 x 10⁻³ M
Let the caffeine be represented by B .
B + H₂O = BH + OH⁻
a - x x x
x² / ( a - x ) = Kb
x² / ( a - x ) = 3.98 x 10⁻¹¹
x is far less than a so a -x is almost equal to a
x² = 3.98 x 10⁻¹¹ x 2.343 x 10⁻³ = 9.32 x 10⁻¹⁴
x = 3.05 x 10⁻⁷
[ OH⁻ ] = 3.05 x 10⁻⁷
pOH = - log ( 3.05 x 10⁻⁷ )
= 7 - log 3.05
= 7 - 0.484 = 6.5
pH = 14 - 6.5 = 7.5
The pH of 455 mg/L of caffeine is 7.5
Using the formula;
Mass concentration = molar concentration × molar mass
Molar mass of caffeine = 194 g/mol
Mass concentration of caffeine = 455 mg/L
Molar concentration = Mass concentration/molar mass
Molar concentration = 455 × 10^-3g/L/194 g/mol
= 0.00235 M
Let Caffeine by depicted by the general formula BH
We can now set up the ICE table as follows;
:B + H2O ⇄ BH + OH^-
I 0.00235 0 0
C - x +x +x
E 0.00235 - x x x
Note that water is present in large excess
Again; pKb of caffeine =10.4
Kb = Antilog[-pKb]
Kb = Antilog [-10.4]
Kb = 3.98 × 10^-11
Kb = [BH] [OH^-]/[:B]
3.98 × 10^-11 = [x] [x]/[ 0.00235 - x ]
3.98 × 10^-11 [ 0.00235 - x ] = [x] [x]
9.4 × 10^-14 - 3.98 × 10^-11x = x^2
x^2 + 3.98 × 10^-11x - 9.4 × 10^-14 = 0
x = 3.1 × 10^-7 M
Recall [BH] = [OH^-] = 3.1 × 10^-7 M
Now;
pOH = - log [OH^-]
pOH = log [3.1 × 10^-7 M]
pOH = 6.5
But;
pH + pOH = 14
pH = 14 - pOH
pH = 14 - 6.5
pH = 7.5
The pH of 455 mg/L of caffeine is 7.5
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Missing parts
Caffeine (C8H10N4O2) is a weak base with a pKb of 10.4. Calculate the pH of a solution containing a caffeine concentration of 455 mg/L.
How can a shoreline be destroyed by a Hurricane?
Answer:
costal erosion
Explanation:
can cause erosion
Answer:
The water piles up with nowhere to go but onto land when it gets to the coast. The rising water, called storm surge, can submerge low-lying areas and towns along the coast. Combined with the crashing waves of the storm, the storm surge can cause demolishing docks, houses, roads, and erode beaches.
Explanation:
What is the approximate vapor pressure when the liquid water boils at about 50°C?
380 mmHg
760 mmHg
100 mmHg
5 mmHg
Answer:
380
Explanation:
If a sample of CO2 contains 48 g of oxygen, how many moles of CO2 are there?
Answer:
0.75 moles of CO2
Explanation:
molar mass of CO2⇒ 44.01 g/mol
molar mass Oxygen ⇒ 31.998 g/mol
divide the mass given by molar mass of oxygen so
48÷31.998= 1.50009376 moles of O
then you use the ration of oxygen to carbon to find the moles of CO2 which is one mole of CO2 for 2 moles of oxygen
1.50009376 moles of O ×[tex]\frac{1}{2}[/tex] = 0.75004688
with sig figs
0.75 moles of CO2
what are the strengths in the bonds of potassium bromide
Answer: Potassium Bromide (KBr) The Ionic bond formed between Potassium and Bromine is created through the transfer of electrons from Potassium (metal) to Bromine (nonmetal).
Explanation: this type of structure departs strongly from that expected for ionic bonding and ... whose roots go back to Max Planck's explanation in 1900 of the properties of ... types of interactions between elementary particles (the strong force, the weak force, ...
Question 11
4 pts
Using the formula 2H202 --> 2H2O + O2, if 7.30 moles of peroxide are
decomposed, how many moles of oxygen will be formed?
Answer:
3.65 mol O₂
Explanation:
Step 1: RxN
2H₂O₂ → 2H₂O + O₂
Step 2: Define
Given - 7.30 mol H₂O₂
Solve - x mol O₂
Step 3: Stoichiometry
[tex]7.30 \hspace{3} mol \hspace{3} H_2O_2(\frac{1 \hspace{3} mol \hspace{3} O_2}{2 \hspace{3} mol \hspace{3} H_2O_2} )[/tex] = 3.65 mol O₂
What does chemical equations and chemical formulas have in common?
Answer:
Chemical symbols refer to chemical elements only. They do not necessarily refer to atoms of that element, but also to ions.
Explanation:
Balance the equations by inserting coefficients as needed.
equation 1:
PCl_{3} + Cl_{2} -> PCl_{5}
PCl3+Cl2⟶PCl5
equation 2:
Mg_{3}N_{2} + HCl -> MgCl_{2} + NH_{3}
Mg3N2+HCl⟶MgCl2+NH3
Answer:
first one is already balanced
2. MgN2+6HCl->3MgCl2+2NH3
Explanation:
To balance the equations, we need to ensure that the same number of each type of atom is present on both sides of the equation. Here's how we can balance the given equations:
Equation 1: PCl₃ + Cl₂ -> PCl₅
In this equation, there are 1 phosphorus (P) atom, 3 chlorine (Cl) atoms, and 5 chlorine (Cl) atoms. To balance the equation, we can put a coefficient of 2 in front of PCl₃ to have 2 phosphorus atoms, and a coefficient of 5 in front of Cl₂ to have 10 chlorine atoms:
2PCl₃ + 5Cl₂ -> PCl₅
Now the equation is balanced with 2 phosphorus atoms and 10 chlorine atoms on both sides.
Equation 2: Mg₃N₂ + HCl -> MgCl₂ + NH₃
In this equation, there are 3 magnesium (Mg) atoms, 2 nitrogen (N) atoms, 2 hydrogen (H) atoms, and 1 chlorine (Cl) atom.
To balance the equation, we can put a coefficient of 3 in front of HCl to have 3 hydrogen atoms, and a coefficient of 2 in front of NH3 to have 2 nitrogen atoms:
Mg₃N₂ + 3HCl -> MgCl₂ + 2NH₃
Now the equation is balanced with 3 magnesium atoms, 2 nitrogen atoms, 6 hydrogen atoms, and 2 chlorine atoms on both sides.
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1.547 grams of hydrated MgSO4 is heated in a crucible. After heating, 0.7554 grams of anhydrous MgSO4 remains in the crucible. How many waters of hydration were attached to the MgSO4
Answer:
7
Explanation:
Let x represent the number of moles of water in the hydrated salt i.e MgSO₄.xH₂O
The following data were obtained from the question:
Mass of MgSO₄.xH₂O = 1.547 g
Mass of anhydrous MgSO₄ = 0.7554 g
Mole of H₂O = x =?
Next, we shall determine the mass of water, H₂O in the hydrated salt, MgSO₄.xH₂O. This can be obtained as follow:
Mass of MgSO₄.xH₂O = 1.547 g
Mass of anhydrous MgSO₄ = 0.7554 g
Mass of H₂O =?
Mass of H₂O = (Mass of MgSO₄.xH₂O) – (Mass of anhydrous MgSO₄)
Mass of H₂O = 1.547 – 0.7554
Mass of H₂O = 0.7916 g
Finally, we shall determine the value of the x as illustrated below:
Mass of MgSO₄.xH₂O = 1.547 g
Molar mass of MgSO₄.xH₂O = 24 + 32 + (16×4) + x[(2×1) + 16]
= 24 + 32 + 64 + x(2 + 16)
= 120 + 18x
Mass of H₂O = 0.7916 g
Molar mass of xH₂O = 18x
Molar Mass of xH₂O/ Molar mass of MgSO₄.xH₂O = mass of xH₂O /Mass of MgSO₄.xH₂O
18x/ 120 + 18x = 0.7916/1.547
Cross multiply
0.7916 (120 + 18x) = 18x × 1.547
94.992 + 14.2488x = 27.846x
Collect like terms
94.992 = 27.846x – 14.2488x
94.992 = 13.5972x
Divide both side by 13.5972
x = 94.992 / 13.5972
x = 7
Thus, the formula for the hydrated salt, MgSO₄.xH₂O is MgSO₄.7H₂O
Number of moles of water, H₂O in the hydrated salt MgSO₄.7H₂O is 7.
The number of moles of attached water molecules is 7.
Mass of hydrated MgSO4 = 1.547 grams
Mass of anhydrous MgSO4 = 0.7554 grams
Number of moles of hydrated MgSO4 = 1.547 grams/120 + 18x
Number of moles of anhydrous MgSO4 = 0.7554 grams /120
Number of moles of anhydrous salt = Number of moles of hydrated salt
0.7554 grams /120 = 1.547 grams/120 + 18x
0.7554(120 + 18x) = 1.547 × 120
90.6 + 13.6x = 185.6
185.6 - 90.6 /13.6 = x
x = 7
The number of moles of attached water molecules is 7.
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The lewis dot notation for two atoms is shown. What is represented by this notation? K loses one portion to CI, K gains one portion from CI, K loses one electron to CI, K gains one electron from CI
Answer:
K loses one electron to CI
Explanation:
The lewis electron dot notation shows only the chemical symbol of the element surrounded by dots to represent the valence electrons.
We have atom of K with one valence electrons
Cl with 7 valence electrons
For an electrostatic attraction to occur, both particles must be charged. To do this, one of the species must lose an electron, and the other gains it.
This will make both species attain a stable octet;
Hence, K will lose 1 electron and Cl will gain the electrons.
Answer:
C: K loses one electron to CI
Explanation:
I took the test and got it correct!!
A hydrocarbon molecule contains carbon and hydrogen atoms in equal numbers. Its molar mass is 130.18 g/mol. What is the molecular formula for the hydrocarbon
Answer:
The molecular formula of the hydrocarbon is C10H10
Explanation:
Here, we are interested in finding the molecular formula for the hydrocarbon.
Since there are equal number of moles of carbon and hydrogen, then we have the molecular formula looking like;
CnHn
Kindly recall that the atomic mass of carbon is 12 a.m.u while that of hydrogen is 1 amu
so calculating the atomic mass of the compound, we have;
12(n) + 1(n) = 130.18
13n = 130.18
n = 130.18/13
n = 10.01
So the molecular formula will be C10H10
Answer:
C10H10
Explanation:
A hydrocarbon is a binary compound of carbon and hydrogen. Hence a hydrocarbon is a compound of the general formula (CH)n
Thus;
(12 + 1) n = 130.18
n= 130.18/13
n = 10
Hence the molecular formula of the compound is C10H10
A 57.07 g sample of a substance is initially at 24.3°C. After absorbing of 2911 J of heat, the temperature of the substance is 116.9 CWhat is the specific heat (SH) of the substance?
Answer:
Approximately [tex]0.551\; \rm J\cdot kg^{-1} \cdot \left(^\circ\! C \right)^{-1}[/tex].
Explanation:
The specific heat of a material is the amount of energy required to increase unit mass (one gram) of this material by unit temperature (one degree Celsius.)
Calculate the increase in the temperature of this sample:
[tex]\Delta T = (116.9 - 24.3)\; \rm ^\circ\! C= 92.6\; \rm ^\circ\! C[/tex].
The energy that this sample absorbed should be proportional the increase in its temperature (assuming that no phase change is involved.)
It took [tex]2911\; \rm J[/tex] of energy to raise the temperature of this sample by [tex]\Delta T = 92.6\; \rm ^\circ\! C[/tex]. Therefore, raising the temperature of this sample by [tex]1\; \rm ^\circ\! C[/tex] (unit temperature) would take only [tex]\displaystyle \frac{1}{92.6}[/tex] as much energy. That corresponds to approximately [tex]31.436\; \rm J[/tex] of energy.
On the other hand, the energy required to raise the temperature of this material by [tex]1\; \rm ^\circ\! C[/tex] is proportional to the mass of the sample (also assuming no phase change.)
It took approximately [tex]31.436\; \rm J[/tex] of energy to raise the temperature of [tex]57.07\; \rm g[/tex] of this material by [tex]1\; \rm ^\circ C[/tex]. Therefore, it would take only [tex]\displaystyle \frac{1}{57.07}[/tex] as much energy to raise the temperature of [tex]1\; \rm g[/tex] (unit mass) of this material by [tex]1\; \rm ^\circ \! C\![/tex]. That corresponds to approximately [tex]0.551\; \rm J[/tex] of energy.
In other words, it takes approximately [tex]0.551\; \rm J[/tex] to raise [tex]1\; \rm g[/tex] (unit mass) of this material by [tex]1\; \rm ^\circ \! C[/tex]. Therefore, by definition, the specific heat of this material would be approximately [tex]0.551\; \rm J\cdot kg^{-1} \cdot \left(^\circ\! C \right)^{-1}[/tex].
Pb12 (s) = Pb+2 (aq)
+
2 ]- (aq)
Answer:
this
Explanation:
What is the unit rate of the better deal? (Number answers only.)
LaTeX: \frac{160\:miles}{5\:gallons}\:or\:\frac{315\:miles}{9\:gallons}160 m i l e s 5 g a l l o n s o r 315 m i l e s 9 g a l l o n s
The better deal has a unit rate of [m] miles per gallon.
1. What is the problem in this activity?
2. Formulate your hypothesis. (List down at least 3 hypotheses)
3. What is the dependent variable?
4. What is the independent variable?
5. Analyze your results. Which type of liquid will prevent the apple from
turning brown?
a. lemon
b. milk
Hello. You forgot to say that this question is about the possibility of using some type of product that prevents cut apples from becoming darker.
Answer and Explanation:
1. The problem with this activity is "What can you put on an apple slice to keep it from turning brown?" The problem in a scientific experiment is the element that provides a question about what is being observed.
2. Hypotheses are assumptions made about what was observed, in addition, hypotheses can answer the question shown in the problem. In the case of apples, the hypotheses can be: "Lemon juice is the most efficient product in delaying the blackening of cut apples." "Water is inefficient in preventing blackened cut apples." "Milk accelerates the blackness of cut apples."
3. The dependent viable is one that needs to be influenced by another element to bring about a result. In the case of the experiment with apples, the dependent variable is the blackening rate of the apple slices.
4. The independent variable, on the other hand, refers to the element that does not need any influence to cause a result, on the contrary, this variable acts on the dependent variable, influencing it. In the case of this experiment, the independent variable is the types of liquid tested to delay the blackening of cut apples.
5. Lemon was the most efficient liquid. Probably this efficiency is related to the lemon's ability to decrease the strength of antioxidants, due to its very low pH.
Concentration data is commonly monitored during a reaction to determine the order with respect to a reactant. Consider the types of observations listed, and determine which order is likely for that reactant. Assume all other factors are held constant.
1. An increase in the concentration of the reactant in solution causes the reaction rate to increase exponentially.
a. first order
b. second order
c. zero order
2. The reaction rate increases in direct proportion to the concentration of the reactant in solution.
a. first order
b. second order
c. zero order
3. The reaction rate is constant regardless of the amount of reactant in solution.
a. first order
b. second order
c. zero order
Answer:
1) first order
2) second order
3) zero order
Explanation:
The curve of a first order reaction shows it to be exponential. In fact for a first order reaction, the concentration at a time t is an exponential function;
[A]t= [Ao] e^-kt
Where
[A]t = concentration at time =t
[Ao]= initial concentration
k= rate constant
t= time
For a second order reaction, the rate of reaction is directly proportional to the concentration of reactants.
For zero order reactions, rate of reaction is independent of concentration hence rate = k(rate constant)
The concentration data has been required for the determination of the rate of reaction. Based on the concentration of reactant and product, the rate has been determined.
1. For the first-order reaction, there has been an exponential increase in the rate of the reaction with the increase in the reactant concentration. The rate has been dependent on the concentration of the reactant.
Thus the correct option is A.
2. Irrespective of the first-order kinetic, in the second-order reaction, the rate of reaction has been directly proportional to the concentration of the reactant in the solution.
Thus option B is correct.
3. The zero-order reaction has been independent of the concentration of the reactant. The rate of reaction has been constant with an increase in the reactant concentration.
Thus option C is correct.
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A sample of an unknown gas weighs 0.419 grams and produced 5.00L of gas at 1.00atm (unknown gas only) and 298.15K, what is the molar mass (g/mole) of this unknown gas
Answer:
molar mass of unknown gas = 1.987 g/mol
Explanation:
First, the number of moles of the unknown gas is found
Using the ideal gas equation: PV = nRT
P = 1.00 atm, V = 5.00 L, T = 298.15 K, R = 0.082 L.atm.mol⁻¹K⁻¹
n = PV/RT
n = (1.00 atm * 5.00 L)/(298.15 K *0.082 L.atm.mol⁻¹K⁻¹)
n = 0.2109 moles
Molar mass = mass/ number of moles
molar mass = 0.419 g/ 0.2109 mols
molar mass of unknown gas = 1.987 g/mol
The molar mass of unknown gas by using ideal gas equation = 1.987 g/mol.
Ideal gas equationThis equation gives the relation between pressure, volume, temperature as given below:
[tex]PV = nRT[/tex]
P = 1.00 atm, V = 5.00 L, T = 298.15 K, R = 0.082 L.atm.mol⁻¹K⁻¹
Substitute the above values in the above equation as follows:
n = (1.00 atm * 5.00 L)/(298.15 K *0.082 L.atm.mol⁻¹K⁻¹)
n = 0.2109 moles
Formula for molar mass[tex]Molar mass = mass/ number of moles[/tex]
Calculate molar mass by using the above equation,
molar mass = 0.419 g/ 0.2109 moles
The molar mass of unknown gas = 1.987 g/mol
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magnesium: atomic number
Answer:
Magnesiums atomic number is 12
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Label the parts of the electric circuit that best correspond to the heart, arteries, veins, and cells.
Answer:
1 ➡️ Cells
2 ➡️ Arteries
3 ➡️ Veins
4 ➡️ Heart
Explanation:
The parts of the electric circuit that best correspond to the heart, arteries, veins, and cells have been properly labeled.
The circulatory system involves the transportation of nutrients, oxygen and water by blood to other the parts of the body.
From the electric circuit, we see that arteries transport blood away from the heart to the other cells in the body. The veins actually return the blood back to the heart from the cells. The heart pumps the blood
The electric circuity diagram has the label 1 bulb analogous to cell, label 2 analogous to arteries, label 3 analogous to veins, and label 4 cell analogous to heart.
What is an electric circuit?The electric circuit has been given as the power source and the conducting wires that allows the flow of the current in the circuit.
In the human body, the heart has been transported the oxygenated blood through the arteries to the cell and carried the deoxygenated blood from the cells back to the heart via veins.
In the circuit, the battery has been the source of the power/blood. The current has been carried from the heart to the cell/bulb through the arteries labeled, 2, and transported back to the battery via veins labeled 3.
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Which of the following is a good definition of matter?
O A. Anything that is made up of light and gravity
O B. Anything that has mass and takes up space
O C. Anything that produces heat and mass
O D. Anything that has energy and creates heat
Answer:
B
Explanation:
I did the question before and got it right.
What occurs after cytokinesis is completed at the end of meiosis I?
O Four haploid cells are formed.
O Two diploid cells are formed.
OTwo haploid cells are formed.
O Four diploid cells are formed.
Answer. After cytokinesis is completed at end of meiosis - I two haploid cells are formed.on:
Answer:
C. TWO HAPLOID CELLS ARE FORMED
Explanation:
I TOOK THE EDGUNITY TEST AND I GOT IT CORRECT
What happens when the elements in group 2 react with water?
Answer:
The Group 2 metals become more reactive towards the water as you go down the Group.
Explanation:
These all react with cold water with increasing vigour to give the metal hydroxide and hydrogen. ... You get less precipitate as you go down the Group because more of the hydroxide dissolves in the water. Summary of the trend in reactivity.
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Rank the following elements in order from least to most number of moles of atoms in a 10.0 g sample: Sn, Si, Se, S
Answer:
[tex]\rm Sn[/tex], [tex]\rm Se[/tex], [tex]\rm S[/tex], [tex]\rm Si[/tex].
Explanation:
The relative atomic mass of an element is numerically equal to the mass (in grams) of one mole of its atoms. This quantity can help estimate the number of moles of atoms in each of these four [tex]10.0\; \rm g[/tex] samples.
Look up the relative atomic mass for each of these four elements (on a modern periodic table.)
[tex]\rm Si[/tex]: [tex]28.085[/tex].[tex]\rm S[/tex]: [tex]32.06[/tex].[tex]\rm Se[/tex]: [tex]78.971[/tex].[tex]\rm Sn[/tex]: [tex]118.710[/tex].The relative atomic mass of [tex]\rm Si[/tex] is (approximately) [tex]28.085[/tex]. Therefore, the each mole of silicon atoms would have a mass of approximately [tex]28.085\; \rm g[/tex]. How many moles of silicon atoms would there be in a [tex]10.0\; \rm g[/tex] sample?
Given:
[tex]m(\rm Si) = 10.0\; \rm g[/tex]. [tex]M(\mathrm{Si}) = 28.085\; \rm g \cdot mol^{-1}[/tex].Number of mole of silicon atoms in the sample: [tex]\displaystyle n(\mathrm{Si}) = \frac{m(\mathrm{Si})}{M(\mathrm{Si})} = \frac{10.0\; \rm g}{28.085\; \rm g \cdot mol^{-1}}\approx 0.356\; \rm mol[/tex].
Similarly:
[tex]\displaystyle n(\mathrm{S}) = \frac{m(\mathrm{S})}{M(\mathrm{S})} = \frac{10.0\; \rm g}{32.06\; \rm g \cdot mol^{-1}}\approx 0.312\; \rm mol[/tex].
[tex]\displaystyle n(\mathrm{Se}) = \frac{m(\mathrm{Se})}{M(\mathrm{Se})} = \frac{10.0\; \rm g}{78.971\; \rm g \cdot mol^{-1}}\approx 0.127\; \rm mol[/tex].
[tex]\displaystyle n(\mathrm{Sn}) = \frac{m(\mathrm{Sn})}{M(\mathrm{Sn})} = \frac{10.0\; \rm g}{118.710\; \rm g \cdot mol^{-1}}\approx 0.0842\; \rm mol[/tex].
Therefore, among these [tex]10.0\; \rm g[/tex] samples:
[tex]n(\mathrm{Sn}) < n(\mathrm{Se}) < n(\mathrm{S}) < n(\mathrm{Si})[/tex].
It is not a coincidence that among these four samples, the one with the fewest number of atoms corresponds to the element with the largest relative atomic mass.
Consider two elements, with molar mass [tex]M_1[/tex] and [tex]M_2[/tex] each. Assume that [tex]n_1[/tex] moles and [tex]n_2[/tex] moles of atoms of each element were selected, such that the mass of both samples is [tex]m[/tex]. That is:
[tex]m = n_1\cdot M_1[/tex].
[tex]m = n_2\cdot M_2[/tex].
Equate the right-hand side of these two equations:
[tex]n_1 \cdot M_1 = n_2\cdot M_2[/tex].
[tex]\displaystyle \frac{n_1}{n_2} = \frac{M_2}{M_1} = \frac{1/M_1}{1/M_2}[/tex].
In other words, the number of moles atoms in two equal-mass samples of two elements is inversely proportional to the molar mass of the two elements (and hence inversely proportional to the formula mass of the two elements.) That explains why in this question, the sample containing the smallest number of atoms corresponds to element with the largest relative atomic mass among those four elements.
According to Avogadro's law, what is characteristic of 1 mole of gas at STP?
A. It occupies 22.4 L.
B. It occupies no volume.
C. It occupies 1 L.
D. It will expand to any volume.
Answer:
A. It occupies 22.4 L
Explanation:
STP (Standard Conditions for Temperature and Pressure) = 22.4 L per mole at 1 atm
Avogadro's Law states that 1 mol at 1 atm occupies 22.4 L.