The number of blocks that can be lifted through this height is 11563 blocks.
How many blocks can be lifted?We know that we define the term energy as the ability to do work, Now we have to consider the fact that we are told that one serving provides 185 kcal. Then we are told that all of this energy is used to lift 1.0-kg blocks through a distance of 7.0 meters.
Given that the energy exerted in lifting each block is;
mgh
m = mass of the block
g = acceleration due to gravity
h = height lifted through
E = 1.0-kg * 9.8 m/s^2 * 7.0 meters = 68.6 J or 0.016 kcal
The number of blocks that can be lifted = 185 kcal/ 0.016 kcal
= 11563 blocks
Learn more about energy:https://brainly.com/question/1932868
#SPJ1
What happens when you cover burning candles with different size glass containers?
Answer:
eventually, they'll always stop burning - how long that takes depends on the glass size
Explanation:
the candle stops burning once it consumes all the oxygen inside the glass. the bigger the glass, the more oxygen there is, but eventually, even that will run out. so, smaller glass means faster, larger slower.
hope that helps
Calcium like to lose how many electron/s to form an ion?Group of answer choices123cannot determine
Answer: the best option to answer the question is the second one (or letter B), "2"
Explanation:
The question requires us to identify how many electrons a calcium (Ca) atom would lose to form an ion.
We can analyze the electron configuration of Ca to understand how many electrons it would lose.
The atomic number of Ca is 20, thus its electron configuration is as it follows:
[tex]1s^2\text{ 2}s^2\text{ 2}p^6\text{ 3}s^2\text{ 3}p^6\text{ 4}s^2[/tex]From the electron configuration, we can see that Ca presents 2 electrons in its valence shell (4s2). To achieve stability, it is easier for Ca to lose these two electrons and form a Ca2+ ion.
Therefore, the best option to answer the question is the second one (or letter B), "2".
PART 1Select Introduction, and for the following unbalanced reactions found in the sim provide the missing coefficients.CoefficientReactant1CoefficientReactant2CoefficientProduct1CoefficientProduct2N2+H2HONH3H2O2COz
They give us the reactions with their respective products and reactants. To balance a reaction we must bear in mind that matter is neither created nor destroyed, it only transforms. So the mass that we have in the reactants must be the same in the products. We verify this by counting the atoms of each element on each side of the reaction.
In the first reaction we have nitrogen and hydrogen. We have 2 nitrogens and 2 hydrogens in the reactants. We start off-balanced in nitrogen, so we place coefficient 2 in the NH3 molecule to get 2NH3. Now that we have 2 nitrogens and 6 hydrogens in the products, we must balance the hydrogen in the reactants. For that, we place the coefficient 3 in the H2 in such a way that there will be 6 hydrogen atoms in the reactants. The equation is balanced and will be:
[tex]N_2+3H_2\rightarrow2NH_3[/tex]We do this same procedure for the other two equations. We count the atoms, we put the coefficients so that the number of atoms is conserved and we count again until the number of atoms of each element is the same on each side of the reaction. For the other two reactions we have:
[tex]2H_2O\rightarrow2H_2+O_2[/tex][tex]CH_4+2O_2\rightarrow CO_2+2H_2O[/tex]What is TRUE about expert witnesses?
A.
They offer personal and professional knowledge.
B.
They are not allowed to practice their testimony.
C.
They are required to link all evidence to the crime.
D.
They have all written a book about their area of expertise.
The true statement about is expert witnesses that they are required to link all evidence to the crime.
So, option C is correct.
Who are expert witnesses?An expert witness is described particularly in common law countries such as the United Kingdom, Australia, and the United States, is a person whose opinion by virtue of education, training, certification, skills or experience, is accepted by the judge as an expert.
Expert witnesses are required or expected to to link all evidence to the crime.
Learn more about expert witnesses at: https://brainly.com/question/4448063
#SPJ1
Calculate the hardness of a water sample which is 35.1 ppm Mg2+ and 65.8 ppm Ca2+.
The hardness of water sample with 35.1 ppm Mg²⁺ and 65.8 ppm Ca²⁺ is 6.215 ppm is 100.9 ppm
Hardness of water is a parameter which is defined by the amount of dissolved minerals in the water like calcium and magnesium. Thus, hard water would have high amount of dissolved minerals in the water. They are sweeter in taste and are good for bones and teeth because of the mineral content
Total hardness of water = Degree of hardness of Mg ²⁺ + Degree of hardness of Ca ²⁺
Degree of hardness Mg ²⁺ = 35.1 ppm
Degree of hardness of Ca ²⁺ = 65.8 ppm
Total hardness = 35.1 + 65.8 = 100.9 ppm
To know more about Hardness of water
https://brainly.com/question/20936443
#SPJ1
4 Al(s) + 302(g)->2Al2O3(s)When 42.39 g of Al and 85.16 g of O2 were reacted, 6.67 grams of aluminum oxidewere obtained. What is the percent yield? (Hint: You need to determine which one isthe limiting reactant and then the theoretical yield).
The reaction presented to us is balanced since we have 4 aluminum atoms and 6 oxygen atoms on both sides of the reaction.
Now, we have a given mass of aluminum and oxygen, we must first determine the moles of each using their molar mass.
Moles of Al
[tex]\begin{gathered} \text{Mol of Al}=GivengAl\times\frac{1molAl}{MolarMass,gAl} \\ \text{Mol of Al}=42.39gAl\times\frac{1molAl}{26.98gAl}=1.57molAl \end{gathered}[/tex]Moles of O2
[tex]\begin{gathered} MolO_2=GivengO_2\times\frac{1molO_2}{MolarMass,gO_2} \\ MolO_2=85.16gO_2\times\frac{1molO_2}{31.998gO_2}=2.66molO_2 \end{gathered}[/tex]Now that we have the number of moles, we will calculate what the limiting reagent is, that is, the reagent that limits the reaction by its number of moles.
To find the limiting reactant we must compare the amount of product obtained with the given amount of reactant separately. The reactant that produces the least amount of product is the limiting reactant.
Using Al as limiting reactant
[tex]\begin{gathered} \text{MolAl}_2O_3=MolAl\times\frac{2molAl_2O_3}{4molAl} \\ \text{MolAl}_2O_3=1.57molAl\times\frac{2molAl_2O_3}{4molAl}=0.785molAl_2O_3 \end{gathered}[/tex]Using O2 as a limiting reactant
[tex]\begin{gathered} \text{MolAl}_2O_3=MolO_2\times\frac{2molAl_2O_3}{3molO_2} \\ \text{MolAl}_2O_3=2.66molO_2\times\frac{2molAl_2O_3}{3molO_2}=1.77molAl_2O_3 \end{gathered}[/tex]Aluminum is the reagent that produces the least amount of aluminum oxide, so the limiting reagent will be Al. And it will produce 0.785 moles of Al2O3. In grams this will be:
[tex]\text{gAl}_2O_3=0.75molAl_2O_3\times\frac{101.95gAl_2O_3}{1molAl_2O_3}=80.03gAl_2O_3[/tex]The percent yield will be:
[tex]\begin{gathered} \text{Percent yield=}\frac{\text{Actual yield}}{Theoretical\text{ yield}}\times100\% \\ \text{Percent yield=}\frac{\text{6}.67gA_{}l_2O_3}{80.03ggA_{}l_2O_3}\times100\%=8.33\% \end{gathered}[/tex]The percent yield will be 8.33%
In a different titration, a solid sample containing some Fe2+ ion weighs 1.705g. It requires 36.44 mL, 0.0244 M KMnO4 to titrate the Fe2+ in the dissolved sample to a pink end point.
a. How many moles MnO4 ion are required?
b. How many moles Fe2+ are there in the sample
c. How many grams of Fe are there in the sample?
d. What is the percent Fe in the sample?
The accurate responses are;
a) Number of moles of permanganate ion = 8.89 * 10^-4 moles
b) Number of moles of iron = 4.4 * 10^-3 moles
c) Mass of iron in the sample = 0.25 g
d) Percentage of iron in the sample = 14.7 %
What is titration?The term titration refers to the kind of reaction in which the amount of substance can be obtained by the accurate determination of the volumes of the substances that have reacted in the process.
a) The number of moles of the permanganate ion that are involved is obtained from;
36.44 /1000 L * 0.0244 M = 8.89 * 10^-4 moles
b) Given that the reaction is 1:5 in the mole ratio of the permanganate ion and the iron III ion
1 mole of permanganate reacts with 5 moles of iron II
8.89 * 10^-4 moles reacts with 8.89 * 10^-4 moles* 5 moles/ 1 mole
= 4.4 * 10^-3 moles
c) Mass of the iron II ion in the sample = 4.4 * 10^-3 moles * 56 g/mol = 0.25 g
d) Percent of the iron in the sample = 0.25 g/1.705g * 100/1
= 14.7 %
Learn more about titration:https://brainly.com/question/2728613
#SPJ1
I need help to this problem
The energy efficiency of this rotating space heater is equal to: C. 64%.
What is energy efficiency?Energy efficiency can bed defined as a process that involves the use of less energy to provide goods and services or perform the same task. This ultimately implies that, energy efficiency helps to reduce air pollution and degradation of the environment.
How to determine the efficiency of this space heater?Mathematically, energy efficiency can be calculated by using this formula:
Energy efficiency = WO/WI × 100
Where:
WO represents the output energy.WI represents the input energy.Note: the amount of energy that was used to produced thermal energy represents the output energy used for heating the room.
Substituting the given parameters into the formula, we have;
Energy efficiency = 896/1,400 × 100
Energy efficiency = 0.64 × 100
Energy efficiency = 64%.
In this context, we can reasonably infer and logically deduce that the space heater's efficiency is equal to 64 percent.
Learn more about efficiency here: brainly.com/question/7672500
#SPJ1
Complete Question:
A rotating space heater used 1,400 joules of energy while heating a room. Of that total, 896 joules produced thermal energy, 181 joules produced kinetic energy, 203 joules produced light energy, and 120 joules produced sound energy. What is the space heater's efficiency?
O 156.25%
O 36%
O 64%
O 56.25%
the atomic number of an atom is the number of _____ in its nucleus and is equal to the number of ____ if the atom is not charged
Answer:
first blank: protons
second black: electrons
Explanation:
The local police department just bought a Reflected Ultraviolet Imaging System (RUVIS) device. What is MOST likely the purpose of this purchase?
A.
to test DNA from blood in their lab
B.
to individualize hair samples
C.
to determine if blood is human or animal
D.
to find and process more fingerprints
Answer:
To find a process more fingerprints (A uv imaging is used to capture and detect substances such as sweat which prints on a surface)
Isopropyl alcohol is mixed with water to produce 32.0% (v/v) alcohol solution.How many milliliters of each component are present in 655 mL of this solution? Assume the volumes are additive.Alcohol: _____________ mL Water: __________ mL
Isopropyl alcohol + water = Solution
Solute = Isopropyl alcohol
Solvent = water
% V/V = mL of solute / 100 ml of solution
Now we have 655 mL of solution.
32.0 % V/V means 32 mL of Isopropyl alcohol dissolved in 100 mL of solution.
So,
32 mL Isopropyl alcohol ------------------- 100 mL Solution
x ------------------- 655 mL Solution
x represents the volume of Isopropyl alcohol in 655 mL of solution
[tex]x\text{ = }\frac{655\text{ mL solution x 32 mL }Isopropylalcohol\text{ }}{100\text{ mL solution}}=\text{ 209.6 mL of }Isopropylalcohol[/tex]Now
Alcohol: 209.6 mL
Water: 655 mL (solution = Alcohol + Water) - 209.6 mL (alcohol) = 445.4 mL of water
Not a timed or graded assignment. Quick thorough answers to each question=amazing review :)
The question requires us to explain how a conversion factor must be used in a dimensional analysis expression.
We can say that a conversion factor is a fraction that we use to convert one unit of measure to another (as long as they measure the same quantity), and it conveys the relationship between these units of measure.
When using a conversion factor in a dimensional analysis process, we need to consider it as a "constant" that multiplies the expression of the dimensional analysis (and always with units that refer to the same measurement). We can't use it as a number in an addition or subctration, for example, or use a conversion factor of volume with an unit of distance.
Name the functional group in thefollowing molecule:NH2A. aldehydeB. amineC. amideD. thiol
The functional group of the given molecule is located at one of the extremes of it, it is:
This functional group is a carbonyl derived group known as amide. We can recognized because of the carbon that has a double bond with the oxygen and at the same time has a simple bond with nitrogen.
It means that the correct answer is amide.
What is the total pressure of the mixture in torr?
In this question, we have to find the total pressure in the container that has 758 mmHg of pressure of cyclopropane, and 0.483 atm of pressure of Oxygen, the answer must be provided in torr:
First thing we need to do is to transform mmHg of cyclopropane to atm
1 atm = 760 mmHg
x atm = 758 mmHg
x = 0.997 atm of pressure of cyclopropane
Now that we have both pressures in atm, we can add them and then we will find the total pressure:
Ptotal = PO2 + Pcyclo
Ptotal = 0.483 + 0.997
Ptotal = 1.48 atm of total pressure
To transform to torr:
1 atm = 760 torr
1.48 atm = x torr
x = 760 * 1.48
x = 1125 torr of pressure is the total pressure
Which subatomic particle is positively charged?ProtonNeutronElectronNone
Explanation:
A proton is a positively charged subatomic particle.
A neutron is a neutrally charged subatomic particle.
An electron is a negatively charged subatomic particle.
Answer:
The first option is correct.
Please select the correct answer for each question!
Answer:1=X
2=Y
3=X
Explanation:
A reaction between liquid reactants takes place at 28.0 degree celcuis in a sealed, evacuated vessel with a measured volume of 15.0L. Measurements show that the reaction produced 10.0g of dinitrogen difluoride gas.
Calculate the pressure of dinitrogen difluoride gas in the reaction vessel after the reaction. You may ignore the volume of the liquid reactants. Round your answer to 2 significant digits.
The pressure of N2F2 will be 1.64 atm.
Given data:
Mass of N2F2 = 66 grams
Molar mass of N2F2 = 66 g/mol
Temperature = 28°C = 273 +28 = 301 Kelvin
volume = 15 L.
Gas constant = 0.08206 L*atm/K* mol
Number of moles can be determined by using the formula:
Number of moles = mass of N2F2 / Molar mass of N2F2
Number of moles = 66 g/ 66 g/mol = 1 moles.
Volume can be determined by using the formula:
P*V = n×R×T
where, P is pressure, V is volume, T is temperature.
P = (n×R×T)/ V
P = 1 * 0.08206 * 301 )/15 = 1.6466 atm.
The pressure of the sulfur tetrafluoride gas is 1.64 atm.
To know more about pressure
https://brainly.com/question/13732472
#SPJ1
Suppose you have an Avogadro’s number of potassium. How many grams does this represent?
According to the given statement one mole of potassium has a mass of 39.1 g.
Briefing:Each element's atomic weight is listed in a periodic table along with how many grams (or an Avogadro number) are needed to make one mole of atoms. Since potassium has an atomic weight of 39.0983 g/mole, a mole of potassium weighs 39.1 g.
What is Avogadro's number explain?Avogadro's number, which is equal to 6.02214076 * 10²³, is the quantity of units in one mole of any material (defined as its molecular weight in grams). Depending on the substance and the nature of the reaction, the units could be electrons, atoms, ions, or molecules.
To know more about Avogadro number visit:
https://brainly.com/question/11907018
#SPJ13
A gas is confined to a cylinder under constant atmospheric pressure,. When the gas undergoes a particular chemical reaction , it releases 135 kJ of heat to its surroundings and does 63 KJ of P-V Work on its surroundings. What are the values of ∆H and ∆E for this process ?
Answer:
[tex]\begin{gathered} \triangle H=-135kJ \\ \triangle E=-198kJ \end{gathered}[/tex]Explanations:
From the question, we are given the following
Amount of heat released to the surroundings = 135kJ
Work done to its surroundings q = 63 kJ
The derivation of the enthalpy at constant pressure is expressed as;
[tex]\triangle H=\triangle U+\triangle(P_{int}V)[/tex]where;
[tex]\begin{gathered} \triangle U\text{ is the internal energy} \\ P_{int_{}}\text{ is the internal pressure} \\ V\text{ is the volume of the gas} \end{gathered}[/tex]Since the cylinder gas is under constant pressure, then the enthalpy will be equal to the work done to have:
[tex]\triangle H=q[/tex]Since q = 63kJ, hence;
[tex]\triangle H=q=-135kJ[/tex]Next is to calculate the change in the change in the internal energy
Using the law of energy conservation which states that the change in internal energy is equal to the heat transferred to, less the work done by, the system. Mathematically;
[tex]\begin{gathered} \triangle E=q+W \\ \triangle E=-135kJ+(-63kJ) \\ \triangle E=-198kJ \end{gathered}[/tex]Hence the change in internal energy for the process is -198kJ
Which compound results from covalent bonding? AgF K2S NaCl CO2
Answer:CO2
Explanation:
A trick that is quick and easy to use when telling covalent bonds from ionic bonds is to look at the atoms that are bonding. If there is a metal involved, then it is ionic bonding (hence AgF, NaCl. and K2S are not covalent bonding as Ag, Na, and K are all metals.
But to be more specific, ionic bonding happens when two ionic or polar atoms (atoms with non-neutral charges,) come together to balance out their charges (as negative charges will be attracted to positive charges and vice versa); the fancy term for this is electrostatic forces. They (usually) give up electrons to another atom, but do not share electrons. Covalent bonding happens when atoms actually share electrons and have their atomic orbitals overlap, meaning that the electrons actually travel through the surrounding volume of both atoms. Ionic bonded atoms will also separate into ions when in a solvent.
Which of the following statements are not true about buffer solutions?
Question 32 options:
The closer the ratio of concentration weak acid/base to the concentration of salt of its conjugate base/acid, the less effective the buffer to resist pH change.
Buffer has acid and base components that can work specifically to resist pH change.
A buffer solution can be prepared by mixing a weak acid and salt of its conjugated base or by mixing a weak base with salt of its conjugated acid.
pH of a buffer solution will not change despite the addition of small quantities of acid or base.
"A buffer solution's pH remains constant, even with small additions of acid or base."
Buffer solutions can react with minor additions of acid or base without changing the concentration of hydrogen ions in the solution. As a result, buffer solutions aid in maintaining a steady pH level throughout chemical reactions.
A weak acid and its conjugate base, or a weak base and its conjugate acid, are mixed together to form a solution called a buffer solution, which is based on water as the solvent. They do not change in pH when diluted or when modest amounts of acid or alkali are added to them.
An illustration would be a buffer created from a weak acid and its salt. It is a solution of acetic acid and sodium acetate CH3COOH + CH3COONa. A mixture of ammonia and ammonium chloride, or NH3aq + NH4Cl aq, is an illustration of a buffer made up of a weak base and its salt.
To know more about buffer solutions, click on the link below:
https://brainly.com/question/27371101
#SPJ9
What is true about the atoms at the start of a chemical reaction compare to the atoms at the end of a net reaction?
The question requires us to comment on what happens to the atoms in a chemical reaction considering the Law of Conservation of Mass.
The Law of Conservation of Mass states that mass is neither created nor destroyed in a chemical reaction. In other words, although the atoms in the reactants rearrange in order to form the products, the mass of both products and reactants must be the same.
Therefore, we can say that, considering the Law of Conservation of Mass, the atoms at the start of a chemical reaction are rearranged compared to the atoms at the end of the reaction, but the mass of reactants and products do not change.
What does the range of a dataset tell us?
A. the value that appears most often in a dataset
B. the difference between the accepted and experimental values
C. the central tendency of the values within a dataset
D. the difference between the lowest and highest values
The range of a data set tells us that the difference between the lowest and highest values (option D).
What is range in statistics?Range in statistics is the length of the smallest interval which contains all the data in a sample i.e. the difference between the largest and smallest observations in the sample.
The range of a data set is a way to measure the central tendency of a data. It is the largest measure or central tendency.
Range describes how well the central tendency represents the data. If the range of a data is large, the central tendency is not as representative of the data as it would be if the range was small.
Learn more about range at: https://brainly.com/question/20607770
#SPJ1
A sample consists of 75.46% carbon, 4.43% hydrogen, and 20.10% oxygen by mass. Its molar mass is about 318 g/mol.
1.) Determine the empirical formula of the sample.
2.) Determine the molecular formula of the sample.
Suppose 2.68 g of barium acetate is dissolved in 300. mL of a 45.0 m M aqueous solution of ammonium sulfa
Calculate the final molarity of acetate anion in the solution. You can assume the volume of the solution doesn't
acetate is dissolved in it.
Round your answer to 3 significant digits.
The term "total moles of a solute contained in a kilogram of a solvent" is used to describe molality. Molal concentration is another name for molality. It is a measurement of a solution's solute concentration.
What is the molarity unit?Molarity is a unit of measurement for the concentration of a material in a specific volume of solution (M). The amount of a solute in one liter of solution is known as its molarity. The molarity of a solution is sometimes referred to as its molar concentration.
As a result, we start by assuming that the reaction is finished and that its volume is constant.
The following is the balanced stoichiometric equation:
BaSO4 + 2NH4(CH3COO) = Ba(CH3COO)2 + (NH4)2SO4.
First, we must identify the surplus reactant and the one that the process has entirely consumed.
For Ba(CH3COO)2,
The formula for moles is (Mass/) (Molar Mass)
Mass of barium acetate is 2.68 g.
Molar mass of barium acetate is 255.43 g/mol.
There are 0.0104 moles, or (2.68/255.43), in total.
Number of moles for (NH4)2SO4 = (Concentration in mol/L) (Volume in L)
Ammonium surface concentration in mol/L is 45 M.
(300/1000) x volume in L = 0.3 L
45 divided by 0.3 to equal 13.5 moles.
According to the reaction's stoichiometric balance, 1 mole of Ba(CH3COO)2 produces 1 mole of (NH4)2SO4.
Ba(CH3COO)2 produces 2 moles of NH4(CH3COO) from 1 mole.
Ba(CH3COO)2 will provide 2 0.0591 moles of NH4(CH3COO), or 0.1182 moles of NH4(CH3COO), from 0.0591 moles of Ba(CH3COO)2.
If NH4(CH3COO) has a molarity, give the number of moles. Volume in L
0.1182 moles are the number of moles.
0.3 L is equal to L of the solution.
NH4(CH3COO) has a molarity of (0.01182/0.3) = 0.0394 M.
Consider that 0.0394 M of NH4(CH3COO) likewise contains 0.0394 M of acetate ion because 1 mole of NH4(CH3COO) includes 1 mole of acetate ion.
To Learn more About molarity, Refer:
https://brainly.com/question/26873446
#SPJ13
A balloon filled to 2.0 L here in Michigan (at 20°C and 752 mmHg) is taken to the top of Mt. Everest. The pressure at the top of Mt. Everest is 253 mmHg, and the balloon grows to a size of 5.1 L. What is the temperature (in °C) at the top of Mt. Everest?
tellsTo answer this question we can use the Combined Gas Law, which tell us that the pressure, volume, and temperature of one situation is equal to the second situation, now let's see how is this formula and how can we apply it to our question:
P1 * V1/T1 = P2 * V2/T2
Now in your question:
1 * 2/20 = 0.33 * 5.1/T2 (I did the transformation mmHg - atm, that makes the question easier, so 752 mmHg = roughly 1 atm and 253 mmHg = 0.33 atm)
2/20 = 1.683/T2
0.1 = 1.683/T2
T2 = 16.8°C
How many moles of solute are present in 250 mL of 4.00 M HCI?
Answer:
Answer. There are 0.1 moles of solute in 250 mL of 0.4 M solution.
Which of the following behaves most like an ideal gas at the conditions indicated?
A H2(g) molecules at 10-3 atm and 200°C
B O2(g) molecules at 20 atm and 200°C
The gas that behaves most like an ideal gas at the conditions indicated is H2(g) molecules at 10-3 atm and 200°C
What is ideal behavior?Recall that a gas is said to show an ideal behavior when the pressure of thee gas is low and the temperature of the gas is high. Recall that, at a high temperature and a low pressure, the interaction that exists between the molecules of the gas is decreased as such the molecules of the gas would tend to move faster.
We can see that the hydrogen gas has a lower pressure at the same temperature hence the interaction that is know to exists between the molecules of the gas is minimal.
Learn more about the ideal gas:https://brainly.com/question/28257995
#SPJ1
Humans have been smelting ore for thousands of years. Ancient humans smelted ore to make all but which of the following
Answer
wiring
Explanation
Ancient humans did make jewelry, weapons and tools by smoltering ore, however, they did not make wires, hence there was no electricity in many mnay years ago.
If 42.6 grams of Al reacts completely with O2 and 57.8 grams of Al2O3 produced, what is the % yield of Al2O3for the reaction? 4Al + 3O2 --------> 2Al2O3Group of answer choices22.3%65.9%55.7%75.2%71.8%
Step 1
Data provided:
The reaction: 4Al + 3O2 => 2Al2O3 (balanced)
The limiting reactant Al (it is said that Al reacts completely)
Mass of Al = 42.6 g
The actual yield = 57.8 g Al2O3
-----------------------
Step 2
Data needed: the molar mass of Al (26.9 g/mol) and Al2O3 (101.9 g/mol)
The theoretical yield:
4 x 26.9 g Al ------- 2 x 101.9 g Al2O3
42.6 g Al ------- X = 80.7 g Al2O3 = theoretical yield
---------------------
Step 3
% yield = (actual yield/theoretical yield) x 100 = (57.8 g/80.7 g) x 100 = 71.6 %
(this is the closest value for one of the options, 71.8 %)
Answer: 71.8 %