Please help solve these chemistry questions!!!

Practice with percent composition.
1. What is the percent composition of Fe if 111.7 g of Fe is recovered from a 159.7 g sample of Fe2O3?




2. What is the percent composition of O if 12 g of O is recovered from a 38 g sample of Cr2O3?




3. Calculate the percent composition of KCl.





4. Calculate the percent composition of N2O5.





Practice with empirical formulas
5. What is the empirical formula for a compound that contains 0.0260 mol C, 0.0325 mol H, and 0.0065 mol O.



Practice with Molecular Formulas
6. Determine the molecular formula for a compound that has an empirical formula of NO2 and a molar mass of 138.015 g/mol.





7. Nicotine is 74.1% C, 8.6% H, and 17.3% N by mass. It’s molar mass is about 160 g/mol.
a. What is it’s empirical formula?




b. What is it’s molecular formula?

Answer:

4.30 moles

Explanation:

You need to use the Ideal Gas Law. The equation looks like this:

PV = nRT

In this equation,

-----> P = pressure (atm)

-----> V = volume (L)

-----> n = moles

-----> R = Ideal Gas Constant (0.08206 atm*L/mol*K)

-----> T = temperature (K)

Before you can plug the given values into the equation and simplify to find "n", you need to convert Celsius to Kelvin. The final answer should have 3 sig figs to match the sig figs of the given values.

P = 3.85 atm                        R = 0.08206 atm*L/mol*K

V = 32.4 L                            T = 80.4 °C + 273.15 = 353.55 K

n = ? moles

PV = nRT

(3.85 atm)(32.4 L) = n(0.08206 atm*L/mol*K)(353.55 K)

124.74 = n(29.012313)

4.30 = n

The number of moles of carbon dioxide produced will be 8.6 moles.

First, let's look at the balanced equation of the reaction. The complete combustion of ethanol gives carbon dioxide and water as follows:

[tex]C_2H_5OH + 3O_2 --- > 2CO_2 + 3H_2O[/tex]

We can see from the equation that the burning of 1 mole of ethanol produces 2 moles of carbon dioxide. In other words, the mole ratio is 1:2.

Thus, with 4.3 moles of ethanol, the amount, in moles, of carbon dioxide that will be produced will be:

                            4.3 x 2 = 8.6 moles

In other words, 8.6 moles of carbon dioxide will be produced from the complete combustion of 4.3 moles of ethanol.

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The second reaction with the volume of 5L will occur faster as compared to the first reaction of volume 10L.

Volume is inversely proportional to the rate of reaction.

As volume increases rate of reaction decreases and as volume decreases rate of reaction increases.

Let's consider a reaction A   →  B.

r is rate of reaction and K is rate constant, A is the concentration of reaction.

r = k(A)

r is directly proportional to the A.

But the concentration of A is in Moles/liters (i.e. moles per unit volume)

r is inversely proportional to the volume of vessel or chamber.

 Hence as volume increases rate of reaction decreases.

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The theoretical yield of the CO2 produced is 4.22 g.

The balanced reaction equation is;

2C2H3Cl + 5O2 ------>2CO2 + 2H2O + 2HCl

Number of moles of  vinyl chloride =  9.10g /62 g/mol = 0.15 moles

Number of moles of oxygen = 7.80g/32 g/mol = 0.24 moles

Now;

2 moles of C2H3Cl reacts with 5 moles of oxygen

0.15 moles of C2H3Cl reacts with 0.15 moles * 5 moles / 2 moles

= 0.375 moles

Hence oxygen is the limiting reactant;

5 moles of oxygen produces 2 moles of CO2

0.24 moles of oxygen produces 0.24 moles * 2 moles /5 moles

= 0.096 moles

Mass of CO2 produced = 0.096 moles * 44 g/mol

= 4.22 g

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Answer:

Techniques and Tests

Qualitative analysis typically measures changes in color, melting point, odor, reactivity, radioactivity, boiling point, bubble production, and precipitation.

The gas is bromine. (This is a fact)

The mass of melted gold to release the energy would be  3, 688. 8 Kg

It is important to note that the formula for  energy is

Q = n × HF

Where

n = number of moles

HF = heat of fusion

Let's find number of moles

235.0 = n × 12.550

number of moles = [tex]\frac{235}{12. 550}[/tex] = 18. 725 moles

The molar mass of Gold is 197g/ mol

We have that;

Number of moles = mass/ molar mass

Mass = number of moles × molar mass

Substitute the values

Mass = 18. 725 × 197

Mass = 3, 688. 8 Kg

Thus, the mass of melted gold to release the energy would be  3, 688. 8 Kg

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Answer:

11.9 moles Cl₂

Explanation:

To find the number of moles, you need to use the Ideal Gas Law. The equation looks like this:

PV = nRT

In this equation,

-----> P = pressure (atm)

-----> V = volume (L)

-----> n = moles

-----> R = constant (0.0821 L*atm/mol*K)

-----> T = temperature (K)

Before you can plug the given values into the equation, you first need to convert Celsius to Kelvin.

P = 33.3 atm                         R = 0.0821 L*atm/mol*K

V = 11.5 L                              T = 120. °C + 273.15 = 393.15 K

n = ? moles

PV = nRT

(33.3 atm)(11.5 L) = n(0.0821 L*atm/mol*K)(393.15 K)

382.95 = n(0.0821 L*atm/mol*K)(393.15 K)

382.95 = (32.2776)n

11.9 = n

Answer:

Potassium chloride.

The element which is losing mass from the above reaction is Cu

Mg(s) + CuSO4(aq) -> MgSO4(aq) + Cu(s)

A compound simply refers to a chemical compound which contains two contains two or more elements which are chemically combined together.

So therefore, the element which is losing mass from the above reaction is Cu

Mg(s) + CuSO4(aq) -> MgSO4(aq) + Cu(s)

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The molecular formula of the compound is C₃H₄.

The molecular formula of the compound is determined from the molecular mass of the compound.

The molecular mass of the compound is derived using the general gas equation as follows:

P₁V₁/T₁ = P₂V₂/T₂

V₂ = P₁V₁T₂/P₂T₁

Volume at STP, V₂ = (415 * 371 * 298(760 * 314)

V₂ = 192.26 mL = 0.192 L

Molar mass of gas = 22.4/0.192 * 0.315 = 36.75 g

Molecular formula is then determined from the mole ratio of the elements;

Carbon = 0.9 * 36.75/12 = 3

Hydrogen = 0.1 * 40/1 = 4

Thus, the molecular formula of the compound is C₃H₄.

In conclusion, the molecular formula of the gas is derived from the molecular mass.

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1.205 × 10²³ atoms of oxygen will be present in 7.51 grams of glycine with formula C₂H5O2N. Details about number of atoms can be found below.

How to calculate number of atoms?

The number of atoms of a substance can be calculated by multiplying the number of moles of the substance by Avogadro's number.

However, the number of moles of oxygen in glycine can be calculated using the following expression:

Molar mass of C₂H5O2N = 75.07g/mol

Mass of oxygen in glycine = 32g/mol

Hence; 32/75.07 × 7.51 = 3.2grams of oxygen in glycine

Moles of oxygen = 3.2g ÷ 16g/mol = 0.2moles

Number of atoms of oxygen = 0.2 × 6.02 × 10²³ = 1.205 × 10²³ atoms

Therefore, 1.205 × 10²³ atoms of oxygen will be present in 7.51 grams of glycine with formula C₂H5O2N.

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Answer:

Percent Yield Fe  =  82.5%

Explanation:

The actual yield is the value produced after an experiment is conducted. The theoretical yield is the value calculated using the balanced chemical equation and atomic/molar masses.

To find the percent yield of iron (Fe), you need to (1) convert grams Al to moles Al (via atomic mass), then (2) convert moles Al to moles Fe (via mole-to-mole ratio from equation coefficients), then (3) convert moles Fe to grams Fe (via atomic mass), and then (4) calculate the percent yield. It is important to arrange the ratios in a way that allows for the cancellation of units. The final answer should have 3 sig figs to reflect the sig figs of the given values.

Atomic Mass (Mg): 24.305 g/mol

Atomic Mass (Fe): 55.845 g/mol

3 Mg + 2 FeCl₃ -----> 2 Fe + 3 MgCl₂

20.5 g Mg           1 mole              2 moles Fe            55.845 g
-----------------  x  -----------------  x  ----------------------  x  -----------------  =  
                           24.305 g           3 moles Mg             1 mole

=  31.4 g Fe

                                     Actual Yield
Percent Yield  =  ----------------------------------  x  100%
                                 Theoretical Yield

                               25.9 g Fe
Percent Yield  =  --------------------  x  100%
                               31.4 g Fe

Percent Yield  =  82.5%

Mechanical waves can help in the treatment of cancer due to heat generated by the high frequency waves.

A mechanical wave is a wave that requires material medium for its propagation, example include;

Sound wave in example of mechanical wave because it requires material medium for its propagation.

High-frequency sound waves (HIFU) is used in the  treatment  of cancer because the strong beam generates heat which is directed to a specific part of a cancer.

The heat generated destroys the cancer cells.

Thus, mechanical waves can help in the treatment of cancer due to heat generated by the high frequency waves.

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All you need to do is to follow these 3 steps.

1. Estimate the number of each kind of atom present in the compound using the chemical formula in order to determine the molar mass of the molecule.

eg. Water

Answer: 63.75 %

Explanation:

The balanced chemical equation for this reaction is:

NaHCO3 + HA = NaA + H2O + CO2

According to the chemical equation, one mole of NaHCO3 will react with one mole of HA to form one mole of NaA, H2O and CO2. All the components are in same mole ratio of 1:1:1:1

So,

Moles of CO2 = weight/molar mass = 0.561/44 = 0.01275 moles

Moles of CO2 will be equal to moles of NaHCO3 = 0.01275 moles

Moles = weight/mass

Weight = moles × mass

So the weight of NaHCO3 = 0.01275 × 84.01 = 1.071 g

The percentage mass of NaHCO3 in the original mixture =(1.071/1.68)× 100% = 63.75 %

Therefore, the percent by mass of NaHCO3 in the original mixture was 63.75 %

The following applies to the above equation:

Brønsted-Lowry acid is the any chemical species that acts as a donor of protons while Brønsted-Lowry base is any chemical species that acts as a proton acceptor.

In the following equation: HCOOH(aq) + PO43-(aq) = HCOO-(aq) + HPO42-(aq)

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1. The resulting concentration will be 0.00044 mol/L

2. The minimum mass of sodium sulfite to add will be 0.4032 grams.

1. Using m1v1=m2v2

  m1 = 0.01 mol/L, v1 = 20 mL, v2 = 450 mL

       m2 = m1v1/v2 = 0.01 x 20/450 = 0.00044 mol/L

2. [tex]Na_2SO_3 + Ca(NO_3)_2 --- > 2NaNO_3 + CaSO_3[/tex]

Mole ratio of the reactants = 1:1

Mole of 80 mL, 0.0400 mol/L Ca(NO3)2 = 80/1000 x 0.0400 = 0.0032 mol

Equivalent mole of Na2SO3 = 0.0032 moles

Mass of 0.0032 moles Na2SO3 = 0.0032 x 126 = 0.4032 grams

Thus, the minimum mass of sodium sulfite to be added must be 0.4032 grams.

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Answer:

a) Ca (s) + 2 H₂O (l) ---> Ca(OH)₂ (aq) + H₂ (g)

b) Al₂O₃ (s) + 3 C (s) + 3 Cl₂ (g) --->  2 AICI₃ (s) + 3 CO (g)

c) 2 FeCl₃ (aq) + 3 H₂S (g) ---> Fe₂S₃ (s) + 6 HCI (aq)

d) CaCO₃ (s) + 2 HCI (aq) ---> CaCl₂ (aq) + CO₂ (g) + H₂O (l)

Explanation:

For an equation to be balanced, there must be an equal amount of each type of atom on both sides of the reaction. The reactants are on the left side and the products are on the right side.

a) ------------------------------------------------------------------------------------------------------

The unbalanced equation:

Ca (s) + H₂O (l) ---> Ca(OH)₂ (aq) + H₂ (g)

Reactants: 1 calcium, 2 hydrogen, 1 oxygen

Products: 1 calcium, 4 hydrogen, 2 oxygen

The balanced equation:

Ca (s) + 2 H₂O (l) ---> Ca(OH)₂ (aq) + H₂ (g)

Reactants: 1 calcium, 4 hydrogen, 2 oxygen

Products: 1 calcium, 4 hydrogen, 2 oxygen

b) ------------------------------------------------------------------------------------------------------

The unbalanced equation:

Al₂O₃ (s) + C (s) + Cl₂ (g) --->  AICI₃ (s) + CO (g)

Reactants: 2 aluminum, 3 oxygen, 1 carbon, 2 chlorine

Products: 1 aluminum, 1 oxygen, 1 carbon, 3 chlorine

The balanced equation:

Al₂O₃ (s) + 3 C (s) + 3 Cl₂ (g) --->  2 AICI₃ (s) + 3 CO (g)

Reactants: 2 aluminum, 3 oxygen, 3 carbon, 6 chlorine

Products: 2 aluminum, 3 oxygen, 3 carbon, 6 chlorine

c) ------------------------------------------------------------------------------------------------------

The unbalanced equation:

FeCl₃ (aq) + H₂S (g) ---> Fe₂S₃ (s) + HCI (aq)

Reactants: 1 iron, 3 chlorine, 2 hydrogen, 1 sulfur

Products: 2 iron, 1 chlorine, 1 hydrogen, 3 sulfur

The balanced equation:

2 FeCl₃ (aq) + 3 H₂S (g) ---> Fe₂S₃ (s) + 6 HCI (aq)

Reactants: 2 iron, 6 chlorine, 6 hydrogen, 3 sulfur

Products: 2 iron, 6 chlorine, 6 chlorine, 3 sulfur

d) ------------------------------------------------------------------------------------------------------

The unbalanced equation:

CaCO₃ (s) + HCI (aq) ---> CaCl₂ (aq) + CO₂ (g) + H₂O (l)

Reactants: 1 calcium, 1 carbon, 3 oxygen, 1 hydrogen, 1 chlorine

Products: 1 calcium, 1 carbon, 3 oxygen, 2 hydrogen, 2 chlorine

The balanced equation:

CaCO₃ (s) + 2 HCI (aq) ---> CaCl₂ (aq) + CO₂ (g) + H₂O (l)

Reactants: 1 calcium, 1 carbon, 3 oxygen, 2 hydrogen, 2 chlorine

Products: 1 calcium, 1 carbon, 3 oxygen, 2 hydrogen, 2 chlorine

The true statements are:

Energy is the ability to do work.

Energy can exist in many form, two of which are kinetic and potential energy.

The worker is holding a filled gas cylinder still gives the gas potential energy by lifting it above the ground.

The molecules of the gas also has kinetic energy by virtue of their constant random motion resulting in thermal energy.

In conclusion, the energy of the filled gas is both potential and kinetic.

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Answer:

H₂(g) = oxidized

N₂(g) = reduced

Explanation:

Oxidized substances lose electrons and increase in oxidation number. Reduced substances gain electrons and decrease in oxidation number.

Lone elements always have an oxidation number of 0. So, N₂(g) and H₂(g) have oxidation numbers of 0.

Within compounds, hydrogen generally always have an oxidation of +1. Therefore, the hydrogen in NH₃(g) has an oxidation number of +1. In order to make the overall compound neutral, the nitrogen in NH₃(g) must have an oxidation number of -3 (to balance the +3 from the 3 hydrogens).

Since H₂(s) is losing electrons (goes from 0 to +1), it is being oxidized. Since N₂(g) is gaining electrons (goes from 0 to -3), it is being reduced.

Taking into account the reaction stoichiometry, 340.0 moles  of methane are produced when 85.1 moles of carbon dioxide gas react with excess hydrogen gas

In first place, the balanced reaction is:

CO₂ + 4 H₄  → CH₄ + 2 H₂O

By reaction stoichiometry (that is, the relationship between the amount of reagents and products in a chemical reaction), the following amounts of moles of each compound participate in the reaction:

The following rule of three can be applied: if by reaction stoichiometry 1 mole of CO₂ form 4 moles of CH₄, 85.1 moles of CO₂ form how many moles of CH₄?

[tex]moles of CH_{4} =\frac{85.1 moles of CO_{2}x4 moles of CH_{4} }{1 moles of CO_{2}}[/tex]

moles of CH₄= 340.4 moles

Then, 340.0 moles  of methane are produced when 85.1 moles of carbon dioxide gas react with excess hydrogen gas

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The concentration will be 12 M. The first option is the correct one.

It is calculated by dividing the number of moles of solute present in a solution by the volume of the solution.

In this case, the number of moles of solute = 1.2 mols

volume of solvent = 100 mL or 0.1 L

Concentration of the solution = 1.2/0.1 = 12 mol/L or 12 M

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The concentration of LiOH in the reaction is 0.103 M

This is a neutralization reaction and the equation of the reaction is written as; H2SO4(aq) + 2LiOH(aq) ---->Li2SO4(aq) + H2O(l)

The average volume of acid used is obtained from;

8.54 + 8.51 + 8.68/ 3 = 8.58 mL

CA = 0.150 M

VA = 8.58 mL

CB = ?

VB= 25.0 mL

NA = 1

NB = 2

CAVA/CBVB = NA/NB

CAVANB = CBVBNA

CB = CAVANB/VBNA

CB = 0.150 * 8.58 * 2/25.0 * 1

CB = 0.103 M

The concentration of LiOH in the reaction is 0.103 M

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0.28 moles of nitrogen gas are there in 6.8 liters at room temperature and pressure (293 K and 100 kPa).

Ideal gas law :

An ideal gas is a gas in which atoms dose not exert any force on each other even after collision which walls and other atoms (inelastic collisions).

Mole definition:

The mole is the amount of compound present in a given system which has molecular mass as that of the mass of carbon12 .carbon 12

Using ideal gas law ,

PV=nRT

Given,

pressure = P = 100kPa

Volume = V = 6.8 Lit

Temperature = room temperature = T = 293 K

R= universal gas constant = 8.314

n= moles = ?

∴[tex]n = \frac{PV}{RT}[/tex]

∴ n = 100 × 6.8 / 8.314 × 293

∴n = 0.28 moles

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Taking into account the definition of pH and pOH, the hydrogen ion concentration will be 1×10⁻⁸ M.

pH is a measure of acidity or alkalinity that indicates the amount of hydrogen ions present in a solution or substance.

The pH is defined as the negative base 10 logarithm of the activity of hydrogen ions, that is, the concentration of hydrogen ions or H₃O⁺:

pH= - log [H⁺]= - log [H₃O⁺]

Similarly, pOH is a measure of hydroxyl ions in a solution and is expressed as the logarithm of the concentration of OH⁻ ions, with the sign changed:

pOH= - log [OH⁻]

The following relationship can be established between pH and pOH:

pOH + pH= 14

In this case, you know that pOH= 6.

Replacing in the relationship established between pH and pOH, the pH can be calculated as:

pH + 6= 14

Solving:

pH= 14 - 6

pH= 8

Replacing in the definition of pH the concentration of H⁺ ions is obtained:

- log [H⁺]= 8

Solving:

[H⁺]= 10⁻⁸

[H⁺]= 1×10⁻⁸ M

In summary, the hydrogen ion concentration will be 1×10⁻⁸ M.

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diphosphorus tetraiodide is the name of the p2I4 compound.

The name of p2I4 is diphosphorus tetraiodide because there are two atoms with phosphorus and four atoms with iodine. We know that 'di' word is used for two while on the other hand, tetra word is used for four.

So we can conclude that diphosphorus tetraiodide is the name of the p2I4 compound.

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The density of the solid is =0.3076g/ml

The mass of solid in flask = 36.65g

The volume of both solid and Toluene = 50ml

The mass of both solid and Toluene = 58.58g

The density of toluene = 0.864g/ml

The density of the solid = X

Note: The density of the solid is calculated from the density of both the solid and toluene.

But the density of solid+ toluene;

=mass/volume

= 58.58g/50ml

= 1.1716g/ml

Therefore the density of solid alone = density of both solid +toluene - density of toluene.

= 1.1716g/ml - 0.864g/ml

= 0.3076g/ml

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I think it should be suspension.