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Ch. 2 - Biochemistry Basics
Norman-McKay- Microbiology: Basic and Clinical Principles 2nd Edition
Norman-McKay2nd EditionMicrobiology: Basic and Clinical PrinciplesISBN: 9780137661619Not the one you use?Change textbook
All textbooksNorman-McKay 2nd EditionCh. 2 - Biochemistry BasicsProblem 4
Chapter 2, Problem 4

Determine the following:
a. The molarity of a solution with 0.5 moles of glucose per liter of water.
b. The concentration (in weight/volume percent) of a solution that contains 20 grams of sodium chloride per liter of water.
c. The concentration (in mg/dL) of a solution with 1 gram of lactic acid per 100 mL of solution.
d. The molarity of a solution with 1 mmol of solute in 1 L of water.

Verified step by step guidance
1
For part (a), recall that molarity (M) is defined as the number of moles of solute divided by the volume of the solution in liters. Use the formula: \(M = \frac{\text{moles of solute}}{\text{volume of solution in liters}}\). Here, you have 0.5 moles of glucose per liter, so substitute these values into the formula.
For part (b), weight/volume percent (% w/v) is calculated as the mass of solute in grams divided by the volume of solution in milliliters, multiplied by 100. Use the formula: \(\% \text{w/v} = \left( \frac{\text{grams of solute}}{\text{mL of solution}} \right) \times 100\). Convert 1 liter to milliliters (1000 mL) and substitute the given values.
For part (c), concentration in mg/dL means milligrams of solute per deciliter of solution. First, convert 1 gram of lactic acid to milligrams (1 g = 1000 mg). Then, note that 100 mL equals 1 deciliter (dL). Use the formula: \(\text{mg/dL} = \frac{\text{mg of solute}}{\text{dL of solution}}\) and substitute the values.
For part (d), molarity is again moles of solute per liter of solution. Here, 1 mmol (millimole) is equal to 0.001 moles. Use the formula: \(M = \frac{\text{moles of solute}}{\text{volume in liters}}\). Since the volume is 1 L, substitute the values accordingly.
After setting up each formula with the correct units and values, perform the arithmetic operations to find the numerical concentrations for each part.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Molarity

Molarity is a measure of the concentration of a solute in a solution, expressed as moles of solute per liter of solution. It is commonly used in chemistry to quantify how much of a substance is dissolved in a given volume, facilitating stoichiometric calculations in reactions.

Weight/Volume Percent Concentration

Weight/volume percent (% w/v) expresses the concentration of a solution as grams of solute per 100 milliliters of solution. It is useful for describing solutions where the solute is a solid dissolved in a liquid, providing a straightforward way to communicate concentration in practical lab settings.
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Unit Conversions in Concentration Measurements

Understanding unit conversions, such as milligrams per deciliter (mg/dL) or millimoles to moles, is essential for accurately interpreting and calculating solution concentrations. These conversions allow comparison and communication of concentrations across different measurement systems.
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Related Practice
Textbook Question

Indicate the true statements and then correct the false statements so that they are true.

a. Isotopes are atoms with differing numbers of protons and the same number of neutrons.

b. A cation is a positive ion.

c. Redox reactions create ions.

d. Equal sharing of electrons leads to polar covalent bonds.

e. Ions are charged atoms.

f. CO2 is an inorganic molecule.

g. Isomers have the same molecular formula but different structures.

h. Adding a base to a solution will decrease the pH.

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Textbook Question

Write the molecular formula for a substance that contains two oxygen molecules, two carbons, and four hydrogen atoms. Be sure to follow the standard conventions of writing molecular formulas.

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Textbook Question

Using the periodic table, answer the following questions:

a. What is the atomic number for lithium (Li)?

b. What is the atomic mass of oxygen (O)?

c. What is the chemical symbol for potassium?

d. How many protons does nitrogen have?

e. How many neutrons does lead have?

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Textbook Question

Select all of the compounds from the following list. If it is not a compound, then state what it is.

a. H2O

b. HCO3-

c. O2

d. H2

e. Li2+

f. C6H12O6

g. H+

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Textbook Question

What ions result when hydrogen donates one electron to fluorine?

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Textbook Question

Select the false statement about salts.

a. Salts are ionic compounds.

b. Salts are formed when an acid and a base react with each other.

c. Salts consist of an anion and a cation component.

d. Salts may be inorganic.

e. Salts are usually acids.

f. Salts are usually hydrophilic.

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