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# Solutions: Concentration and Mass Calculations

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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

https://brainmass.com/chemistry/organic-chemistry-bonding/solutions-concentration-and-mass-calculations-210126

#### Solution Summary

The solution investigates two subjects: concentration or molarity of the solutions and attractive forces between molecules. The solution is detailed and well presented.

\$2.19

## Solution Concentration Calculations

I.Solution Preparation

A.For this experiment, you must calculate the mass of solute, nickel (II) nitrate, needed to prepare the four following standard solutions:
1.0.050 M Ni(NO3) 2in a 100 mL volumetric flask.
2.0.100 M Ni(NO3) 2in a 100 mL volumetric flask.
3.0.150 M Ni(NO3) 2in a 100 mL volumetric flask.
4.0.200 M Ni(NO3) 2in a 100 mL volumetric flask.
1.Solution Concentration
2.Mass of Solute Needed
3.Absorption at 400 nm, trial number 1
4.Absorption at 400 nm, trial number 2
5.Absorption at 400 nm, trial number 3
6.Average Absorption at 400 nm
C.Enter the data for Solution Concentration and Mass of Solute for the blank and each of the four nickel (II) nitrate solutions.

II.Preparation of the Calibration Curve

A.A technician has run three trials and has obtained absorbance readings for each of the solutions.
B.The technician's results are as follows:
1.For the blank, 0.000 M Ni(NO3) 2, the results for Absorbance are: 0.00, 0.00 and 0.00.
2.For the 0.050 M Ni(NO3) 2 solution, the results for Absorbance are: 0.23, 0.24, and 0.26.
3.For the 0.100 M Ni(NO3) 2 solution, the results for Absorbance are: 0.50, 0.49, and 0.49.
4.For the 0.150 M Ni(NO3) 2 solution, the results for Absorbance are: 0.75, 0.75, and 0.74.
5.For the 0.200 M Ni(NO3) 2 solution, the results for Absorbance are: 1.03, 0.99, and 1.00.
C.Record each of these values in the appropriate cell of your Excel® file.
D.Calculate the average Absorbance, record them in the appropriate cells of your Excel® file, and use these values for the Absorbance points on your graph.
E.Use the chart function of Excel® to plot an XY (scatter) diagram comparing Absorbance to concentration (molarity).
F.Plot your results with the independent variable, molarity of the nickel solution, along the abscissa, or x-axis, and with the dependent variable, Absorbance, along the ordinate, or y-axis.Move the columns of you Excel® chart as needed to obtain the correct plot; you may use additional "sheets" if you wish to accomplish this.
G.Print a copy of the graph.
H.On your print copy, use a straightedge to draw the best straight line through the points.Do not "connect the dots."The line does not need to touch each point; it should be the most representative straight line so that there will be about the same number of dots above as below the line and at reasonably the same distance from the line.

III.Determination of Nickel

A.The technician, using a nickel (II) nitrate, Ni(NO3)2, solution of unknown concentration, has run three trials and has obtained the following Absorbance readings:0.42, 0.38, and 0.41.
B.Record these results in your Excel® file with the average Absorbance of these results.
C.Calculate the average absorbance and use this value for an absorbance point on your graph. Use the printed graph from above, find the average Absorbance of the unknown on the y-axis, and place a point on the straight line at that Absorbance.
D.Using the observed absorbance and your calibration curve, determine the molarity, or moles per liter, of the nickel (II) nitrate, Ni(NO3) 2, unknown solution. Again use the printed graph; find the point on the x-axis directly below the point on the straight line that represents the Absorbance of the unknown. This is the molarity of the unknown nickel (II) nitrate solution.
E.Enter this information into your Excel® file.
F.Calculate the mass of nickel (II) nitrate that would be found in 100 mL of the unknown solution and enter it into your Excel® file.
G.Plot a second graph with the independent variable, molarity of the nickel solution, along the abscissa, or x-axis, and with the dependent variable, Absorbance, along the ordinate, or y-axis.This graph will include the point for the unknown nickel (II) nitrate solution.
H.Review your graph to ensure that you have included the appropriate labels:Chart Title, the value that the x-axis represents, and the value that the y-axis represents.

1.Show your calculations determining the mass of nickel (II) nitrate required to prepare 100 mL of each of the four standard solutions.