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# Concentrations and Solutions

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1) The Equilibrium constant Kp for the reaction
2SO2(g) + O2(g) &#61663;---&#61664; 2SO3(g)
Is 5.60 x 10^4 at 350 degrees C. The initial pressures of SO2 is 0.350 atm and the initial pressure of O2 is 0.762 atm at 350 degrees C. When a mixture equillibtrates, is the total pressure less than or greater than the sum of the initial pressures (1.112 atm)?

2) You are working as a lab assistant and are tasked to prepare an acetic acid - sodium acetate buffer solution with a pH of 4.00 ± 0.02. What molar ratio of CH3COOH to CH3COONa should be used?

3) The equilibrium constant Kc for the reaction
H2(g) + Br(g) &#61663;-----&#61664; 2HBr(g)
Is 2.18 x 10^6 at 730 degrees C. Starting with 3.20 moles of HBr in a 12.0-L reaction vessel, calculate the concentrations of H2, Br2, and HBR at equilibrium.

4) Assuming equal concentrations of conjugate base and acid, which one of the following mixtures is suitable for making a buffer solution with an optimum pH of 4.6 - 4.8?
a. CH3COO2Na / CH3COOH (Ka = 1.8 x 10-5)
b. NH3 / NH4Cl (Ka(NH4+) = 5.6 x 10-10)
c. NaOCl / HOCl (Ka = 3.2 x 10-8)
d. NaNO2 / HNO2 (Ka = 4.5 x 10-4)
e. NaCl / HCl

5) You have 500.0 mL of a buffer solution containing 0.20 M acetic acid (CH3COOH) and 0.30 M sodium acetate (CH3COONa). What will the pH of this solution be after the addition of 20.0 mL of 1.00 M NaOH solution?

Ka = 1.8 x 10-5

6) 50.00 mL of 0.10 M HNO2 (nitrous acid) was titrated with 0.10 M KOH solution. After 25.00 mL of KOH solution was added, what was the pH in the titration flask? (Given Ka = 4.5 x 10-4)

7) The solubility product for CrF3 is Ksp = 6.6 x 10-11. What is the molar solubility of CrF3?

8) The Ksp for Ag3PO4 is 1.8 x 10-18. Determine the Ag+ ion concentration in a saturated solution of Ag3PO4.

9) Will a precipitate of MgF2 form when 300 mL of 1.1 x 10-3 M MgCl2 solution are added to 500 mL of 1.2 x 10-3 M NaF? Ksp (MgF2) = 6.9 x 10-9

https://brainmass.com/chemistry/acids-and-bases/concentrations-and-solutions-259954

#### Solution Summary

This solution explains:

1) How to determine concentration of reactants and products in an equilibrium reaction.
2) How to prepare a buffer solution with a specific pH.
3) How to calculate a molar solubility.
4) How to calculate ion concentration in a concentrated solution.

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## Solutions: Concentration and Mass Calculations (Fully Worked)

Please see the attached file for the fully formatted problem(s).

Activity - Solution Calculations

1. What is the Zn(NO3)2 percent composition by weight of a solution made by dissolving 15.5 g of zinc nitrate, Zn(NO3) 2, in 45.0 g of water? (%)

2. How many moles of sodium hydroxide, NaOH, are required to prepare 2.00 L of 0.331 M solution? (mol)

3. What is the molarity of a solution, if 3.44 g of potassium hydroxide, KOH, are dissolved in water to make 150.0 mL of solution? (M)

4. What volume (mL) of 0.400 M solution can be prepared by dissolving 4.71 g of KOH in water?

5. What weight of potassium bromide (g), KBr, could be recovered by evaporating 577.5g of 15.0 percent KBr solution to dryness?

6. Calculate the weight of hydrogen chloride (g) in 52.8 mL of concentrated HCl (12.00M) solution.

7. A sulfuric acid solution has a density of 1.73 g/mL and contains 80.0 percent H2SO4 by weight. What is the molarity (M) of this solution?
a. 14.1 M
b. 1.38 M
c. 2.16 M
d. 13.2 M

8. On the average, glucose (C6H12O6) makes up about 0.100% by weight of human blood. How much glucose (g) is there in 3.98 kg of blood?

9. What volume of 1.00M HCl stock solution is necessary to prepare 143.3 mL of 0.250 M HCl? (mL)

10. A sample of potassium hydrogen oxalate, KHC2O4, weighing 0.656 g, was dissolved in water and titrated with 18.47 mL of an NaOH solution. Calculate the molarity of the NaOH solution. (M)

11. Sulfuric acid reacts with sodium hydroxide according to this equation:
H2SO4(aq) + 2 NaOH (aq) &#8594; Na2SO4(aq) + 2 H2O(l)
A 10.00 mL sample of the H2SO4 solution required 16.71 mL of 0.309 M NaOH for neutralization.
Calculate the molarity of the acid. (M)

12. Given the molar mass of sulfuric acid of 98 g/mol, what mass of sulfuric acid (g) is necessary to prepare 449 mL of 15.0% (w/v)?

13. What is the molar mass of a solute that yields 1.00 molar solution when 117 g of the solute is dissolved in water such that the total volume of the solution is 2.00 L?
a. 58.5 g/mol
b. 56.5 g/mol
c. 46.1 g/mol
d. 117.0 g/mol
e. 234.0 g/mol

14. What volume of solution (mL) is needed when preparing a 0.500% (w/v) solution from 0.176 g of NaOH (40.0 g/mol)?

15. Given the molarity of the solution as 0.344 mol/L and the molar mass of the solute as 26.0 g/mol, what is the mass-volume concentration of the solute (g/L) in the solution?

16. What volume of solvent (mL) is necessary to prepare 5.00% (v/v) from 24.6 mL acetic acid ?

1. Match the VSEPR models for the chemicals below and check the property each chemical possesses.
Matching pairs
Oxygen difluoride, OF2
Carbon disulfide, CS2

2. Match the VSEPR models for the chemicals below and check the property each chemical possesses.
Matching pairs
Methane, CH4
Fluoromethane, CH3F

3. Build VSEPR model for the chemical below and check property the chemical possess.
Hydrogen peroxide, H2O2
1. The chemical is trigonal around the oxygen and polar
2. The chemical is bent around the oxygen and polar
3. The chemical is tetrahedral around hte oxygen and polar
4. The chemical is linear around the oxygen and polar

4. Build VSEPR model for the chemical below and check property the chemical possess.
Ammonia, NH3
1. The chemical is pyramidal and nonpolar
2. The chemical is trigonal and nonpolar
3. The chemical is trigonal and polar
4. The chemical is pyramidal and polar

5. For the substance below, check all the attractive forces between molecules that are expected.
Oxygen difluoride, OF2
1. Dipole - Dipole
2. London Dispersion Force (LDF)
3. Hydrogen Bonding
4. Others

6. For the substance below, check all the attractive forces between molecules that are expected.
Methane, CH4
1. Diple - Dipole
2. London Dispersion Force (LDF)
3. Hydrogen bonding
4. Others

7. For the substance below, check all the attractive forces between molecules that are expected.
Carbon disulfide, CS2
1. Dipole - Dipole
2. London Dispersion Force (LDF)
3. Hydrogen bonding
4. Others

8. For the substance below, check all the attractive forces the molecule is expected to posessess.
Fluoromethane, CH3F
1. Dipole - Dipole
2. London Dispersion Force (LDF)
3. Hydrogen bonding
4. Others

9. For the substance below, check all the attractive forces between molecules that are expected.
Hydrogen peroxide, H2O2
1. Dipole - Dipole
2. London Dispersion Force (LDF)
3. Hydrogen bonding
4. Others

10. For the substance below, check all the attractive forces between molecules that expected.
Ammonia, NH3
1. Dipole - Dipole
2. London Dispersion Force (LDF)
3. Hydrogen bonding
4. Others

11. Check all statement below that is/are absolutely true for a chemical to be considered polar.

1. The chemical cannot have lone pair electrons around the central atom
2. The chemical must have polar bonds
3. The chemical cannot be bent
4. The chemical must be nonsymmetric

12. Consider the hypothetical situation that water has a linear molecular shape. Select the correct statement for this hypothetical situation.
1. If water is a linear molecule, then London dispersion force would not be one of its IMF
2. If water is a linear molecule, then it will probably have higher intermolecular forces
3. If water is a linear molecule, then it would probably be nonpolar
4. If water is a linear molecule, then its boiling point will probably still remain at 100 C

13. When will hydrogen bonding occur?
1. H-bonding occurs when the molecule contains fluorine atom, such as CF4
2. H-bonding occurs when the H of one molecule is attracted to F, O, or N of another molecule.
3. H-bonding occurs only for the water molecule
4. None of these statements are true

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