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Nadusha1986 [10]
2 years ago
14

A 1.87 L aqueous solution of KOH contains 155 g of KOH . The solution has a density of 1.29 g/mL . Calculate the molarity ( M ),

molality ( m ), and mass percent concentration of the solution
Chemistry
1 answer:
lbvjy [14]2 years ago
5 0

Answer:

[KOH] = 1.47 M

[KOH] = 1.22 m

KOH = 6.86 % m/m

Explanation:

Let's analyse the data

1.87 L is the volume of solution

Density is 1.29 g/mL → Solution density

155 g of KOH → Mass of solute

Moles of solute is (mass / molar mass) = 2.76 moles.

Molarity is mol/L → 2.76 mol / 1.87 L = 1.47 M

Let's determine, the mass of solvent.

Molality is mol of solute / 1kg of solvent

We can use density to find out the mass of solution

Mass of solution - Mass of solute = Mass of solvent

Density = Mass / volume

1.29 g/mL = Mass / 1870 mL

Notice, we had to convert L to mL, cause the units of density.

1.29 g/mL . 1870 mL = Mass → 2412.3 g

2412.3 g - 155 g = 2257.3 g of solvent

Let's convert the mass of solvent to kg

2257.3 g / 1000 = 2.25kg

2.76 mol / 2.25kg = 1.22 m (molality)

% percent by mass = mass of solute in 100g of solution.

(155 g / 2257.3 g) . 100g = 6.86 % m/m

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penicillin. an important antibiotic (antibacterial agent), was discovered accidentally by the scottish bacteriologist alexander
dmitriy555 [2]

Answer:

mass percent of carbon       = 57.78 %

mass percent of hydrogen   = 6.40 %

mass percent of nitrogen    = 8.96 %

mass percent of oxygen    = 20.49 %

mass percent of sulfur     =  10.24 %

Explanation:

Given data

Molecular formula = C₁₄H₂₀N₂O₄S

molecular mass (total mass) = 312.39 g/mol

Percentage of carbon = ?

Percentage of hydrogen = ?

Percentage of oxygen = ?

Percentage of nitrogen = ?

Percentage of sulfur = ?

Solution

1st we find out number of moles of each element from the molecular formula

  Number of moles of carbon  = 14 mol

  Number of moles of hydrogen   = 20 mol

  Number of moles of nitrogen   = 2 mol

  Number of moles of oxygen  = 4 mol

  Number of moles of sulfur   = 1 mol

Now we find out the mass of each element

as we know that

     <em>mass = number of moles × molecular mass</em>

 mass of carbon  = 14 mol × 12 g/mol

 mass of carbon  = 168 g

 mass of hydrogen   = 20 mol × 1 g/mol

 mass of hydrogen   = 20 g

 mass of nitrogen   = 2 mol × 14 g/mol

 mass of nitrogen   = 28 g

 mass of oxygen  = 4 mol × 16 g/mol

 mass of oxygen  = 64 g

 mass of sulfur   = 1 mol × 32 g/mol

 mass of sulfur   =  32 g

now we find out the mass percent of each element

<em>         mass percent = ( mass ÷ total mass ) × 100</em>

 mass percent of carbon  = ( 168 g ÷ 312.39 g/mol ) × 100

 mass percent of carbon  = 57.78 %

 mass percent of hydrogen   = ( 20 g ÷ 312.39 g/mol ) × 100

 mass percent of hydrogen   = 6.40 %

 mass percent of nitrogen   = ( 28 g ÷ 312.39 g/mol ) × 100

 mass percent of nitrogen   = 8.96 %

 mass of oxygen  =( 64 g ÷ 312.39 g/mol ) × 100

 mass percent of oxygen  = 20.49 %

 mass percent of sulfur   = ( 32 g ÷ 312.39 g/mol ) × 100

 mass percent of sulfur   =  10.24 %

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Arrange the following in order of increasing boiling point: RbCl, CH3Cl, CH3OH, CH4. A. CH3OH &lt; CH4 &lt; CH3Cl &lt; RbCl B. R
rosijanka [135]

Answer:

E. CH₄ < CH₃Cl < CH₃OH < RbCl

Explanation:

The molecule with the stronger intermolecular forces will have the higher boiling point.

The order of strength of intermolecular forces (strongest first) is

  • Ion-Ion
  • Hydrogen bonding
  • Dipole-dipole
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RbCl is a compound of a metal and a nonmetal. It is an ionic compound, so it has the highest boiling point.

CH₃Cl has a C-Cl polar covalent bond. It has dipole-dipole forces, so it has the second lowest boiling point.

CH₃OH has an O-H bond. It has hydrogen bonding, so it has the second highest boiling point.

CH₄ has nonpolar covalent C-H bonds. It has only nonpolar bonds, so the only attractive forces are London dispersion forces. It has the lowest boiling point.

Thus, the order of increasing boiling points is

CH₄ < CH₃Cl < CH₃OH < RbCl

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2 years ago
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Julli [10]

Answer : Option C) Atomic Size

Explanation : The atomic radius of the elements is found to be decreasing if we go from left to right in the modern periodic table. Accordingly, Z_{eff} increases as the number of shielding electrons present in the atomic nucleus of the periodic elements which lies in the same row remains constant while the number of protons in each atomic shell increases.

The effective nuclear charge Z_{eff} of an atom is defined as the net positive charge which is felt by the valence electron of the atomic element.

When Z_{eff} is observed to decrease, it is seen that the atomic radius grows in size. So, it explains the inverse relationship between both. This phenomenon occurs, because there is more screening of the electrons from the nucleus taking place, which is observed due to decrease the attraction between the electron and the nucleus.

7 0
2 years ago
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A gas is heated from 263.0 K to 298.0 K and the volume is increased from 24.0 liters to 35.0 liters by moving a large piston wit
Triss [41]

Answer:

The final pressure is approximately 0.78 atm

Explanation:

The original temperature of the gas, T₁ = 263.0 K

The final temperature of the gas, T₂ = 298.0 K

The original volume of the gas, V₁ = 24.0 liters

The final volume of the gas, V₂ = 35.0 liters

The original pressure of the gas, P₁ = 1.00 atm

Let P₂ represent the final pressure, we get;

\dfrac{P_1 \cdot V_1}{T_1} = \dfrac{P_2 \cdot V_2}{T_2}

P_2 = \dfrac{P_1 \cdot V_1 \cdot T_2}{T_1 \cdot V_2}

P_2 = \dfrac{1 \times 24.0 \times 298}{263.0 \times  35.0} = 0.776969038566

∴ The final pressure P₂ ≈ 0.78 atm.

4 0
2 years ago
Which is stronger, the strong force (SF) or the electromagnetic force (EMF)? Describe how they battle each other in the nucleus.
Roman55 [17]

Answer:uclear Force that holds together the nucleus of an atom. electromagnetic force. ... They are unstable because the Strong Force that would hold them together if the protons and neutrons were closer is weakened because the protons and neutrons get too far apart.

Explanation:

6 0
2 years ago
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