Comprehensive GOB Chemistry Exam Review Guidance

Q1. A pediatric patient weighs 43.5 lb. The dose for ibuprofen for this age group is 8.50 mg/kg. How many mg of ibuprofen should this patient receive?

Background

Topic: Unit Conversions and Dosage Calculations

This question tests your ability to convert between units (pounds to kilograms) and apply dosage calculations using dimensional analysis.

Key Terms and Formulas

• 1 kg = 2.205 lb

• Dosage (mg) = Patient mass (kg) × Dose (mg/kg)

Step-by-Step Guidance

1. Convert the patient's weight from pounds to kilograms using the conversion factor: $1 \ \text{kg} = 2.205 \ \text{lb}$.

2. Set up the dimensional analysis to cancel out pounds and solve for kilograms.

3. Multiply the patient's mass in kilograms by the dosage (8.50 mg/kg) to find the total milligrams needed.

4. Set up the multiplication but do not calculate the final value yet.

Try solving on your own before revealing the answer!

Final Answer: 168 mg

First, convert 43.5 lb to kg: $43.5 \ \text{lb} \times \frac{1 \ \text{kg}}{2.205 \ \text{lb}} = 19.7 \ \text{kg}$ (rounded to 3 sig figs).

Then, $19.7 \ \text{kg} \times 8.50 \ \text{mg/kg} = 168 \ \text{mg}$.

The patient should receive 168 mg of ibuprofen.

Q2. Children’s Tylenol Oral Suspension is sold as a solution with a concentration of 160 mg/5.0 mL. For a patient of four to five years, the dose for a fever is 7.5 mL. How many milligrams of Tylenol is the patient receiving with this dose?

Background

Topic: Solution Concentration and Dosage Calculations

This question tests your ability to use solution concentration to determine the amount of solute (Tylenol) in a given volume.

Key Terms and Formulas

• Concentration: $\frac{160 \ \text{mg}}{5.0 \ \text{mL}}$

• Amount (mg) = Volume (mL) × Concentration (mg/mL)

Step-by-Step Guidance

1. Set up the ratio to find the amount of Tylenol per 1 mL: $\frac{160 \ \text{mg}}{5.0 \ \text{mL}}$.

2. Multiply the prescribed dose (7.5 mL) by the concentration (mg/mL).

3. Set up the multiplication but do not calculate the final value yet.

Try solving on your own before revealing the answer!

Final Answer: 240 mg

First, $\frac{160 \ \text{mg}}{5.0 \ \text{mL}} = 32 \ \text{mg/mL}$.

Then, $7.5 \ \text{mL} \times 32 \ \text{mg/mL} = 240 \ \text{mg}$.

The patient receives 240 mg of Tylenol.

Q3. A patient has a measured temperature of 38.2 °C. Convert this temperature to Fahrenheit and state whether or not this is considered to be a fever.

Background

Topic: Temperature Conversions

This question tests your ability to convert between Celsius and Fahrenheit and apply clinical knowledge about fever thresholds.

Key Terms and Formulas

• Temperature conversion: $T_\text{F} = T_\text{C} \times \frac{9}{5} + 32$

• Normal body temperature: ~37 °C (98.6 °F); fever is typically > 38 °C (100.4 °F)

Step-by-Step Guidance

1. Plug the Celsius temperature into the conversion formula: $T_\text{F} = 38.2 \times \frac{9}{5} + 32$.

2. Calculate $38.2 \times \frac{9}{5}$ first.

3. Add 32 to the result from step 2 to get the Fahrenheit temperature.

4. Compare the result to the fever threshold (100.4 °F) to determine if it is a fever.

Try solving on your own before revealing the answer!

Final Answer: 100.8 °F, yes

$38.2 \times \frac{9}{5} = 68.76$; $68.76 + 32 = 100.8$ °F.

Since 100.8 °F is above the fever threshold, this is considered a fever.

Q4. An athlete runs a 5K. How many meters is this? Report your answer to 3 significant figures.

Background

Topic: Metric Conversions and Significant Figures

This question tests your ability to convert kilometers to meters and report the answer with the correct number of significant figures.

Key Terms and Formulas

• 1 kilometer (km) = 1000 meters (m)

• Significant figures: Report to 3 significant digits

Step-by-Step Guidance

1. Recognize that 5K means 5 kilometers.

2. Multiply 5 kilometers by 1000 to convert to meters.

3. Express the answer in scientific notation with 3 significant figures.

Try solving on your own before revealing the answer!

Final Answer: $5.00 \times 10^3$ m

5 km × 1000 = 5000 m, which is $5.00 \times 10^3$ m (3 significant figures).

Q5. A solution has a density of 1.06 g/mL. What is the volume of a 25 g sample of this solution?

Background

Topic: Density Calculations

This question tests your ability to use the density formula to solve for volume.

Key Terms and Formulas

• Density formula: $\text{Density} = \frac{\text{Mass}}{\text{Volume}}$

• Rearranged: $\text{Volume} = \frac{\text{Mass}}{\text{Density}}$

Step-by-Step Guidance

1. Identify the given values: mass = 25 g, density = 1.06 g/mL.

2. Rearrange the density formula to solve for volume.

3. Set up the calculation: $\text{Volume} = \frac{25 \ \text{g}}{1.06 \ \text{g/mL}}$.

4. Do not calculate the final value yet.

Try solving on your own before revealing the answer!

Final Answer: 24 mL

$\text{Volume} = \frac{25}{1.06} = 23.6$ mL, rounded to 2 significant figures is 24 mL.

Q6. Complete the following table (naming ionic compounds):

Background

Topic: Nomenclature of Ionic Compounds

This question tests your ability to write names and formulas for ionic compounds, including those with polyatomic ions and transition metals.

Key Terms and Formulas

• Binary ionic compounds: Metal + Nonmetal (ending in -ide)

• Polyatomic ions: Use the name of the ion as is

• Transition metals: Indicate charge with Roman numerals

Step-by-Step Guidance

1. For each formula, identify the cation and anion.

2. Write the name using the rules for ionic compounds.

3. For each name, write the correct chemical formula.

4. Be sure to use Roman numerals for transition metals as needed.

Try solving on your own before revealing the answer!

Final Answer:

Formula	Name
MgCl2	magnesium chloride
Li3P	lithium phosphide
Na3N	sodium nitride
Mg3(PO4)2	magnesium phosphate
Cu3N	copper (I) nitride
FeO	iron (II) oxide
NaNO3	sodium nitrate
Cu(OH)2	copper (II) hydroxide

Q7. Complete the following table (molecular compounds):

Background

Topic: Molecular Compounds, Lewis Structures, Molecular Geometry, Polarity, and Intermolecular Forces

This question tests your ability to name molecular compounds, draw their Lewis structures, determine geometry, and identify polarity and intermolecular forces.

Key Terms and Formulas

• Lewis structure: Shows bonding and lone pairs

• Electron pair geometry: Arrangement of electron groups

• Molecular shape: Arrangement of atoms

• Polarity: Distribution of charge

• IMF: Intermolecular forces (dispersion, dipole-dipole, hydrogen bonding)

Step-by-Step Guidance

1. Name each compound using prefixes (e.g., di-, tetra-).

2. Draw the Lewis structure for each molecule.

3. Determine the electron pair geometry and molecular shape using VSEPR theory.

4. Assess whether the molecule is polar or nonpolar.

5. Identify the most prevalent intermolecular force.

Try solving on your own before revealing the answer!

Final Answer:

Compound	Name	Draw the molecule	Electron pair geometry	Molecular shape	Polar or nonpolar	Most prevalent IMF
SBr2	Sulfur dibromide	Bent structure	Tetrahedral	Bent	Polar	Dipole-dipole
CCl4	Carbon tetrachloride		Tetrahedral	Tetrahedral	Nonpolar	Dispersion

Q8. Draw the expanded structure for the following molecule. State the molecular formula and calculate the molar mass. Show molar mass calculation.

Background

Topic: Organic Structure Drawing, Molecular Formula, and Molar Mass Calculation

This question tests your ability to interpret and draw organic structures, determine the molecular formula, and calculate molar mass using atomic weights.

Key Terms and Formulas

• Molecular formula: Count each atom in the structure

• Molar mass: Sum of (number of atoms × atomic mass) for each element

Step-by-Step Guidance

1. Carefully count the number of each type of atom (C, H, N, O) in the expanded structure.

2. Write the molecular formula based on your count.

3. List the atomic masses: C = 12.01 g/mol, H = 1.008 g/mol, N = 14.01 g/mol, O = 16.00 g/mol.

4. Multiply the number of each atom by its atomic mass and sum the results to get the molar mass.

5. Set up the calculation but do not compute the final value yet.

Try solving on your own before revealing the answer!

Final Answer: C8H15NO, 141.21 g/mol

Counted atoms: 8 C, 15 H, 1 N, 1 O.

Molar mass: $(8 \times 12.01) + (15 \times 1.008) + (1 \times 14.01) + (1 \times 16.00) = 141.21$ g/mol.