Answer:
Formulas
3.2 Determining Empirical and Molecular Formulas
Learning Objectives
By the end of this section, you will be able to:
Compute the percent composition of a compound
Determine the empirical formula of a compound
Determine the molecular formula of a compound
The previous section discussed the relationship between the bulk mass of a substance and the number of atoms or molecules it contains (moles). Given the chemical formula of the substance, one may determine the amount of the substance (moles) from its mass, and vice versa. But what if the chemical formula of a substance is unknown? In this section, these same principles will be applied to derive the chemical formulas of unknown substances from experimental mass measurements.
Percent Composition
The elemental makeup of a compound defines its chemical identity, and chemical formulas are the most succinct way of representing this elemental makeup. When a compound’s formula is unknown, measuring the mass of each of its constituent elements is often the first step in the process of determining the formula experimentally. The results of these measurements permit the calculation of the compound’s percent composition, defined as the percentage by mass of each element in the compound. For example, consider a gaseous compound composed solely of carbon and hydrogen. The percent composition of this compound could be represented as follows:
%H=mass Hmass compound×100%
%C=mass Cmass compound×100%
If analysis of a 10.0-g sample of this gas showed it to contain 2.5 g H and 7.5 g C, the percent composition would be calculated to be 25% H and 75% C:
%H=2.5g H10.0g compound×100%=25%
%C=7.5g C10.0g compound×100%=75%
EXAMPLE 3.9
Calculation of Percent Composition
Analysis of a 12.04-g sample of a liquid compound composed of carbon, hydrogen, and nitrogen showed it to contain 7.34 g C, 1.85 g H, and 2.85 g N. What is the percent composition of this compound?
Solution
To calculate percent composition, divide the experimentally derived mass of each element by the overall mass of the compound, and then convert to a percentage:
%C=7.34g C12.04g compound×100%=61.0%%H=1.85g H12.04g compound×100%=15.4%%N=2.85g N12.04g compound×100%=23.7%
The analysis results indicate that the compound is 61.0% C, 15.4% H, and 23.7% N by mass.
Check Your Learning
A 24.81-g sample of a gaseous compound containing only carbon, oxygen, and chlorine is determined to contain 3.01 g C, 4.00 g O, and 17.81 g Cl. What is this compound’s percent composition?
ANSWER:
12.1% C, 16.1% O, 71.8% Cl
Determining Percent Composition from Molecular or Empirical Formulas
Percent composition is also useful for evaluating the relative abundance of a given element in different compounds of known formulas. As one example, consider the common nitrogen-containing fertilizers ammonia (NH3), ammonium nitrate (NH4NO3), and urea (CH4N2O). The element nitrogen is the active ingredient for agricultural purposes, so the mass percentage of nitrogen in the compound is a practical and economic concern for consumers choosing among these fertilizers. For these sorts of applications, the percent composition of a compound is easily derived from its formula mass and the atomic masses of its constituent elements. A molecule of NH3 contains one N atom weighing 14.01 amu and three H atoms weighing a total of (3 × 1.008 amu) = 3.024 amu. The formula mass of ammonia is therefore (14.01 amu + 3.024 amu) = 17.03 amu, and its percent composition is:
%N=14.01amu N17.03amuNH3×100%=82.27%%H=3.024amu H17.03amuNH3×100%=17.76%
This same approach may be taken considering a pair of molecules, a dozen molecules, or a mole of molecules, etc. The latter amount is most convenient and would simply involve the use of molar masses instead of atomic and formula masses, as demonstrated Example 3.10. As long as the molecular or empirical formula of the compound in question is known, the percent composition may be derived from the atomic or molar masses of the
pls help me i really need help
Answer:
13. t = 1183 min and 0.50 M.
14. [tex]t_{1/2}=2.67x10^{-8}hr[/tex]
Explanation:
Hello!
13. In this case, according to the units, we infer this is a second-order reaction which has the following integrated rate law:
[tex]\frac{1}{[A]} =\frac{1}{[A]_0} +kt[/tex]
Which can be solved for the time as shown below:
[tex]t=\frac{ \frac{1}{[A]}-\frac{1}{[A]_0}}{k}[/tex]
Thus, we plug in the given concentrations and rate constant to obtain:
[tex]t=\frac{ \frac{1}{0.250M}-\frac{1}{0.850M}}{0.002387M^{-1}min^{-1}}\\\\t= 1183min[/tex]
For the second part, we proceed by using the same rate constant and the new initial concentration as follows:
[tex]\frac{1}{[A]} =\frac{1}{[A]_0} +kt\\\\\frac{1}{[A]} =\frac{1}{0.750M} +0.680M^{-1}min^{-1}*0.996min\\\\\frac{1}{[A]} =1.99,M[/tex]
[tex][A]=0.50M[/tex]
14. In this case, according to the units of the rate constant, we infer this is a zeroth-order reaction, therefore we compute the half-life has shown below:
[tex]t_{1/2}=\frac{[A]_0}{2k}[/tex]
Thus, we plug in to obtain:
[tex]t_{1/2}=\frac{2.696x10^{-6}M}{2*50.5M*hr^{-1}}[/tex]
[tex]t_{1/2}=2.67x10^{-8}hr[/tex]
Best regards!
What is the definition of lava?
Answer:
Lava, magma (molten rock) emerging as a liquid onto Earth's surface. The term lava is also used for the solidified rock formed by the cooling of a molten lava flow.
Explanation:
5. Which model shows the progression of the movement of particles from fastest to slowest as thermal energy is removed?
Answer:
A nivel microscópico y en el marco de la Teoría cinética, es el total de la energía cinética media presente como el resultado de los movimientos aleatorios de átomos y moléculas o agitación térmica, que desaparecen en el acto.
Explanation:
esoes
can u bang a teacher in class
Answer:
Explanation:
Feel free to bang me- your teacher
Answer:
depends lol
Explanation:
The lattice energy of a salt is 350 kJ/mol and the solvation energies of its ions add up to 320 kJ/mol for the preparation of a 0.50 M solution. In the preparation of this solution would the solution get colder or warmer
Answer:
It would get colder
Explanation:
The lattice energy is the energy involved in the disruption of interactions between the ions of the salt. In this case, we have: ΔHlat = 350 kJ/mol > 0, so it is an endothermic process (the energy is absorbed).
The solvation energy is the energy involved in forming interactions between water molecules and the ions of the salt. In this case, we have: ΔHsolv = 320 kJ/mol > 0, so it is an endothermic process (the energy is absorbed).
The dissolution process involve both processes: the disruption of ion-ion interactions of the salt and the solvation process. Thus, the enthalphy change (ΔHsol) in the preparation of the solution is calculated as the addition of the lattice energy and solvation energy:
ΔHsol= ΔHlat + ΔHsolv = 350 kJ/mol + 320 kJ/mol = 370 kJ/mol
370 kJ/mol > 0 ⇒ endothermic process
Since the preparation of the solution is an endothermic process, it will absorb energy from the surroundings, so the solution would get colder.
What key assumption of Bohr’s model would a Solar S y stem model of the atom violate? What was the theoretical basis for this assumption?
Answer:
See explanation
Explanation:
The solar system consists of the sun at the core surrounded by all the planets in their proper order. Similarly, the Bohr model of the atom upholds Rutherford's planetary model in which the atom was said to have a positive core surrounded by electrons moving in orbits just as the planets orbit round the sun.
The difference between the two models is that electrons are able to move from one energy level to another. This assumption violates the principles of the solar system because the position of the planets are fixed in their orbits.
The theoretical basis behind this assumption is that each spectral line is produced by the transition of electrons from one energy level to another.
f) How many neutrons are there in the nucleus of arsenic?
1. Neodymium
2. Selenium
3. Strontium
Explanation:
How many neutrons are there in the nucleus of arsenic?42 neutrons
The nucleus consists of 33 protons (red) and 42 neutrons (blue).
117 milligrams (mg) of purified product was isolated from a chemical reaction. This experimental yield of product represents a 89.0% yield for the reaction. Calculate the theoretical yield, in milligrams (mg), for this reaction. Enter your answer as digits only, no units, using the proper number of significant figures.
Answer:
131 mg
Explanation:
Percent yield = 89%
Actual yield = 117 mg
Percent yield is given by
[tex]\text{Percent yield}=\dfrac{\text{Actual yield}}{\text{Theoretical yield}}\times 100\\\Rightarrow 89=\dfrac{117}{\text{Theoretical yield}}\times 100\\\Rightarrow \text{Theoretical yield}=\dfrac{117}{89}\times 100\\\Rightarrow \text{Theoretical yield}=131.46\approx 131\ \text{mg}[/tex]
The theoretical yield, for this reaction is 131 mg.
What is the term for the chemical reaction that makes soap?
Answer: soaps are a sodium or potassium salts of long chain fatty acids.when triglycerides in fat/oil react with aqueous NaOH or KOH,they are converted into soap and glycerol.This is called alkaline hydrolysis of esters.Since this reaction leads to formation of soap, it is called the saponification process.
Explanation:
Please match the correct type of reaction to its name.
How many particles are in 67.9 grams of water (H2O)?
Answer:
3.769022740695677
Explanation:
Answer:We get 1.81×1024 water molecules... Explanation: We assess the molar quantity of water in the usual way... Number of moles=massmolar mass.
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please help. im freaking out rn. i have like 40 missing assignments please
Answer:
I'm pretty sure its the one that says very little at the beginning but if I get it wrong I'm sorry
Convert 9.24 x 1023 molecules CO2 to moles
1.53 mol CO₂
General Formulas and Concepts:Math
Pre-Algebra
Order of Operations: BPEMDAS
Brackets Parenthesis Exponents Multiplication Division Addition Subtraction Left to RightChemistry
Atomic Structure
Avogadro's Number - 6.022 × 10²³ atoms, molecules, formula units, etc.Stoichiometry
Using Dimensional AnalysisExplanation:Step 1: Define
9.24 × 10²³ molecules CO₂
Step 2: Identify Conversions
Avogadro's Number
Step 3: Convert
Set up: [tex]\displaystyle 9.24 \cdot 10^{23} \ molecules \ CO_2(\frac{1 \ mol \ CO_2}{6.022 \cdot 10^{23} \ molecules \ CO_2})[/tex]Multiply/Divide: [tex]\displaystyle 1.53437 \ mol \ CO_2[/tex]Step 4: Check
Follow sig fig rules and round. We are given 3 sig figs.
1.53437 mol CO₂ ≈ 1.53 mol CO₂
How many grams of CO are needed to react with an excess of Fe2O3 to produce 209.7 g Fe? Equation Fe2O2(g) + 3CO(g) -> 3CO2(g) + 2Fe(g)
Answer: 157.3 g CO
Explanation:
Fe2O3 + 3CO —> 3CO2 + 2Fe [1 mol + 3 mol —> 3 mol + 2 mol]
3 mol CO —> 2 mol Fe
3*28g —> 2*56g
amt CO 3*28*209.7/(2*56) = 157.3g
How many grams of a nonelectrolyte (78.2 g/mol) must be dissolved in 1 kg of solvent to obtain a freezing point of solution of 1.57ºC? The freezing point of the pure solvent is 4.72ºC and the freezing point depression constant of the solvent is 3.89 ºC/m
Answer Tu mama por si acaso
Explanation:
jkand
Which of the following properties do solids and liquids have in common?
definite volume
definite temperature
definite smell
definite shape
Answer:
definite volume
Explanation:
Both solids and liquids have a definite volume: The difference is that solids have definite shape while liquids do not -liquids take the shape of their containers-.
Having a definite volume is why liquids cannot be compressed, a property that is used in hydraulic systems.
A car is traveling 100 miles per hour. How many feet does this car travel in 5 seconds?
Answer:
5280 feet per mile. 5280 feet divided 60 minutes then divide by 60 gives you the feet per second. multiply by 5.... 7 and 1/3 feet in 5 seconds.
Which of the following is considered a complex (Macro)molecule?
Glucose
DNA
Carbon dioxide
Answer:
it is Glucose hope it helps
Answer:
Glucose and DNA
Explanation:
Complex macromolecules are the combination of more than two molecules which are large and complex. The major types of complex macromolecules consists of 4 types which are carbohydrates, lipids, proteins, and nucleic acids.
Glucose is one of the carbohydrates, while DNA is another form of nuclei acid.
Western art criticism unique in that
Answer:
they are a lot tougher and are expecting only greatness, sort of like theater critiques.
Explanation:
A student measures a boiling water bath with two different thermometers. The digital thermometer records the temperature as 100.2°C and has an uncertainty of 0.1°C. The analog thermometer records the temperature as 99.0°C and has an uncertainty of 0.5°C. What is the percent uncertainty of each thermometer? And what is the percent error given that water boils at 100.0°C?
Answer:
Explanation:
Measurement made = 100.2 °C
uncertainty = 0.1°C
percent uncertainty = .1 x 100 / 100.2
= .099 %
2 nd thermometer :
Measurement made = 99.0 °C
uncertainty = 0.5°C
percent uncertainty = .5 x 100 / 99
= .505 %
Percent error :
1 st thermometer
Error = 100.2 - 100 = .2 °C
measurement = 100.2
percent error = .2 x 100 / 100.2
= .1996 %
2 nd thermometer
Error = 100.00 - 99 = 1.00 °C
measurement = 99
percent error = 1 x 100 / 99
= 1.01 %
The percent error of digital thermometer is 0.1996 %. The percent error of analog thermometer is 1.01 %.
Percent uncertainty is the measure of degree of error region with the uncertainty in the measurement.
The percentage error is the difference in the measurement of the values with actual value.
Computation for percent uncertainty and percent errorThe percent uncertainty (%U) is calculated by:
[tex]\% U=\rm \dfrac{Uncertainty}{Measurement}\;\times\;100[/tex]
The percent error (%E) is calculated by:
[tex]\%E=\rm \dfrac{error\;value-actual\;value}{error\;value}\;\times\;100[/tex]
The percent uncertainty and error for digital thermometer is given as:The Recorded temperature = 100.2 degree Celsius
The actual temperature = 100 degrees Celsius
The uncertainty in the readings is 0.1 degree Celsius
The percent uncertainty is given by:
[tex]\%U=\dfrac{0.1}{100.2}\;\times\;100\\\\ \%U=0.099\;\%[/tex]
The percent uncertainty of digital thermometer is 0.099 %.
The percent error is given by:
[tex]\% E=\dfrac{100.2-100}{100.2}\;\times\;100 \\\\\% E=\dfrac{0.2}{100.2}\;\times\;100\\\\ \% E=0.1996\;\%[/tex]
The percent error of digital thermometer is 0.1996 %.
The percent uncertainty and error for analog thermometer is given as:The Recorded temperature = 99 degree Celsius
The actual temperature = 100 degrees Celsius
The uncertainty in the readings is 0.5 degree Celsius
The percent uncertainty is given by:
[tex]\%U=\dfrac{0.5}{99}\;\times\;100\\\\ \%U=0.505\;\%[/tex]
The percent uncertainty of analog thermometer is 0.505%.
The percent error is given by:
[tex]\% E=\dfrac{100-99}{99}\;\times\;100 \\\\\% E=\dfrac{1}{99}\;\times\;100\\\\ \% E=1.01\;\%[/tex]
The percent error of analog thermometer is 1.01 %.
Learn more about percent error, here:
https://brainly.com/question/3105259
What is the name of the compound O7I9
Answer:
question not clear can u rewrite
Ethanol, the alcohol in alcoholic beverages, has a density of 0.7893 g/mL. What is the shipping weight of a 5.0-gallon container of pure ethanol if the bottle weighs 1.82 lb and the shipping container and packaging weigh 0.76 lb
Answer:
16.09 kg
Explanation:
To solve this problem first we convert those 5.0 gallons of ethanol into liters:
5.0 gallons * [tex]\frac{3.78L}{1gallon}[/tex] = 18.9 LNow we calculate the mass of that volume of ethanol, using its density:
We convert 18.9 L ⇒ 18.9 * 1000 = 18900 mL
Mass = Density * VolumeMass = 0.7893 g/mL * 18900 mL = 14917.77 gFinally we convert the masses of the bottle and shipping container and packaging and add them to the mass of ethanol:
1.82 lb * 453.592 = 825.54 g0.76 lb * 453.592 = 344.73 gTotal Mass = 14917.77 g + 825.54 g + 344.73 g = 16088.04 gSo the shipping weight would be 16088.04 g, or 16.09 kg
Some antacid tables contain aluminum hydroxide. The aluminum hydroxide reacts with stomach acid according to the equation: Al(OH)3 + 3HCl →AlCl3 + 3H2O. Determine the moles of stomach acid (HCl) required if a tablet contains 8.89 moles of Al(OH)3.
Answer:
26.67 mol HCl
Explanation:
Al(OH)₃ + 3HCl → AlCl₃ + 3H₂O
In order to solve this problem, we need to convert Al(OH)₃ moles to HCl moles.
To do so we use the stoichiometric ratios of the balanced reaction:
8.89 mol Al(OH)₃ * [tex]\frac{3molHCl}{1molAl(OH)_{3}}[/tex] = 26.67 mol HClThus 26.67 moles of HCl would react completely with 8.89 moles of Al(OH)₃.
How do you balance this equation?
Answer:
HC₂H₃O₂ + NaHCO₃ —> NaC₂H₃O₂ + CO₂ + H₂O
The coefficients are: 1, 1, 1, 1, 1
Explanation:
_HC₂H₃O₂ + _NaHCO₃ —> _NaC₂H₃O₂ + _CO₂ + _H₂O
To balance an equation, we simply do a head count of the individual elements and ensure they are balanced on both side.
For the above equation, we shall balance it as :
HC₂H₃O₂ + NaHCO₃ —> NaC₂H₃O₂ + CO₂ + H₂O
Reactant:
H = 5
C = 3
O = 5
Na = 1
Product:
H = 5
C = 3
O = 5
Na = 1
From the above, we can see that each element is the same on both side of the equation. Thus the equation is already balanced
HC₂H₃O₂ + NaHCO₃ —> NaC₂H₃O₂ + CO₂ + H₂O
The coefficients are: 1, 1, 1, 1, 1
A gas sample of 5 moles, has a volume of 95 L. How many moles of the same gas should I add to obtain a volume of 133 L at the same temperature and pressure.
How many grams of sulfur must be burned to give 100.0 g of So2
Answer:
50 g of S are needed
Explanation:
To star this, we begin from the reaction:
S(s) + O₂ (g) → SO₂ (g)
If we burn 1 mol of sulfur with 1 mol of oxygen, we can produce 1 mol of sulfur dioxide. In conclussion, ratio is 1:1.
According to stoichiometry, we can determine the moles of sulfur dioxide produced.
100 g. 1mol / 64.06g = 1.56 moles
This 1.56 moles were orginated by the same amount of S, according to stoichiometry.
Let's convert the moles to mass
1.56 mol . 32.06g / mol = 50 g
What is true about the inertia of two cars, Car A of mass 1,500 kilograms and Car B of mass 2,000 kilograms?
OA.
Car A and Car Bhave the same inertia.
B.
Car A has more inertia than Car B.
Oc.
Car Bhas more inertia than Car A.
ОО
D.
Both the cars have negligible inertia.
I’m
Answer:
Car B has more inertia than Car A
Explanation:
Given that,
Mass of car A = 1500 kg
Mass of car B = 2000 kg
Inertia is directly proportional to the mass of an object. Inertia is the measure of the mass of an object.
In this case, the mass of car B is more than that of car A, it means the inertia of car B is more than that of car A.
Hence, the correct option is (c) "Car B has more inertia than Car A".
Determine the chemical equation for the reaction between Fe3+ and Cu2+ with NH3
Answer:
Cu2 + 4 NH3 = Cu (NH3) 42+
so - - >
[Cu (NH3) 6] ^ 2+
Explanation:
Iron is a metal. The structure of iron is described as a lattice of positive ions in a sea of
electrons. Which of the following statements about iron are correct?
1 iron conducts electricity because the electrons are free to move
2 iron has a high melting point due to the strong covalent bonds
3 iron is an alloy
4 iron is malleable because the layers of atoms can slide over one another
A. 1 only
B. 1 and 3
C. 1 and 4
D. 2, 3 and 4
Answer: 1and 4
Explanation: iron is an element not an alloy. An ionic lattice is not bonded covalently.
A chemistry student needs 50.0ml of tetrahydrofuran for an experiment. By consulting the CRC Handbook of Chemistry and Physics, the student discovers that the density of tetrahydrofuran is . Calculate the mass of tetrahydrofuran the student should weigh out. Be sure your answer has the correct number of significant digits.
Answer:
44.45 g of tetrahydrofuran.
Explanation:
From the question given above, the following data were obtained:
Volume of tetrahydrofuran = 50 mL
Density of tetrahydrofuran = 0.889 g/mL
Mass of tetrahydrofuran =?
Density of a substance is simply defined as the mass of the substance per unit volume of the substance. Mathematically, density is expressed as shown below:
Density = mass / volume
With the above formula, we shall determine the mass of tetrahydrofuran needed. This can be obtained as follow:
Volume of tetrahydrofuran = 50 mL
Density of tetrahydrofuran = 0.889 g/mL
Mass of tetrahydrofuran =?
Density = mass / volume
0.889 = mass / 50
Cross multiply
Mass = 0.889 × 50
Mass of tetrahydrofuran = 44.45 g
Therefore, the student should weigh out 44.45 g of tetrahydrofuran.