CHEM 114 Exam 1 Study Guidance

Q1. What is the correct formula for the oxide ion?

Background

Topic: Ions and Ionic Compounds

This question tests your understanding of how ions are formed, specifically the oxide ion, which is derived from oxygen.

Key Terms and Concepts:

• Ion: An atom or molecule with a net electric charge due to the loss or gain of electrons.

• Oxide ion: The ion formed when oxygen gains electrons.

Step-by-Step Guidance

1. Recall that oxygen is in Group 16 (6A) of the periodic table and has 6 valence electrons.

2. Determine how many electrons oxygen needs to gain to achieve a stable octet (8 valence electrons).

3. When oxygen gains electrons, it forms an anion. Figure out the charge on this ion.

4. Write the symbol for the oxide ion, including its charge.

Try solving on your own before revealing the answer!

Q2. What is the formula for aluminum nitrate?

Background

Topic: Naming and Writing Formulas for Ionic Compounds

This question tests your ability to write the correct chemical formula for a compound formed between aluminum and the nitrate ion.

Key Terms and Formulas:

• Aluminum ion: $\mathrm{Al^{3+}}$

• Nitrate ion: $\mathrm{NO_3^-}$

Step-by-Step Guidance

1. Write the symbols and charges for the aluminum ion and the nitrate ion.

2. Use the criss-cross method to balance the charges so the compound is neutral.

3. Write the formula, using parentheses if more than one polyatomic ion is needed.

Try solving on your own before revealing the answer!

Q3. A serving of fish contains 50 g protein and 4 g of fat. If protein has a caloric value of 4 kcal/g and fat has 9 kcal/g, how many kcal are in the serving?

Background

Topic: Nutrition and Caloric Content

This question tests your ability to calculate total caloric content from macronutrients using their caloric values.

Key Formulas:

• Calories from protein: $\text{grams of protein} \times 4\ \text{kcal/g}$

• Calories from fat: $\text{grams of fat} \times 9\ \text{kcal/g}$

• Total calories: $\text{calories from protein} + \text{calories from fat}$

Step-by-Step Guidance

1. Calculate the calories provided by the protein: $50\ \text{g} \times 4\ \text{kcal/g}$.

2. Calculate the calories provided by the fat: $4\ \text{g} \times 9\ \text{kcal/g}$.

3. Add the two results to find the total caloric content.

Try solving on your own before revealing the answer!

Q4. The main type of intermolecular forces between particles of ammonia (NH3) are ________.

Background

Topic: Intermolecular Forces

This question tests your understanding of the types of intermolecular forces present in molecules, specifically ammonia.

Key Terms:

• Hydrogen bonding

• Dipole-dipole attractions

• Dispersion forces

• Ionic bonds

Step-by-Step Guidance

1. Identify the molecular structure of ammonia ($\mathrm{NH_3}$) and the types of atoms present.

2. Determine if hydrogen is bonded to a highly electronegative atom (N, O, or F).

3. Recall which intermolecular force is strongest in molecules with N-H, O-H, or F-H bonds.

4. Compare the options and select the most significant force present in ammonia.

Try solving on your own before revealing the answer!

Q5. Why is it important that radioisotopes used in diagnostic tests have short half-lives?

Background

Topic: Nuclear Chemistry and Medical Applications

This question tests your understanding of the properties of radioisotopes and their use in medicine.

Key Terms:

• Radioisotope: A radioactive isotope of an element.

• Half-life: The time required for half of the radioactive atoms in a sample to decay.

Step-by-Step Guidance

1. Consider what happens to a radioisotope as it decays (emission of radiation).

2. Think about the effects of radiation on the human body, especially in a medical context.

3. Evaluate why a short half-life would be beneficial for diagnostic tests.

4. Eliminate options that do not relate to patient safety or effectiveness of the test.

Try solving on your own before revealing the answer!

Q6. An anion always ________.

Background

Topic: Ions and Ionic Compounds

This question tests your understanding of the definition and properties of anions.

Key Terms:

• Anion: A negatively charged ion formed when an atom gains electrons.

Step-by-Step Guidance

1. Recall the definition of an anion and how it is formed.

2. Review the options and identify which one correctly describes an anion.

3. Eliminate options that describe cations or other types of particles.

Try solving on your own before revealing the answer!

Q7. A patient has a temperature of 38.5 °C. What is the temperature in degrees Fahrenheit?

Background

Topic: Temperature Conversions

This question tests your ability to convert temperatures between Celsius and Fahrenheit scales.

Key Formula:

• $\mathrm{T_{\!F}} = \frac{9}{5} \mathrm{T_{\!C}} + 32$

Step-by-Step Guidance

1. Identify the given temperature in Celsius: $38.5\ ^\circ\mathrm{C}$.

2. Plug this value into the conversion formula: $\mathrm{T_{\!F}} = \frac{9}{5} \times 38.5 + 32$.

3. Calculate $\frac{9}{5} \times 38.5$ as an intermediate step.

4. Add 32 to the result from the previous step to get the temperature in Fahrenheit.

Try solving on your own before revealing the answer!

Q8. Which of the following is a homogeneous mixture?

Background

Topic: Classification of Matter

This question tests your ability to distinguish between homogeneous and heterogeneous mixtures, elements, and compounds.

Key Terms:

• Homogeneous mixture: A mixture with uniform composition throughout.

• Heterogeneous mixture: A mixture with non-uniform composition.

Step-by-Step Guidance

1. Review the definition of a homogeneous mixture.

2. Analyze each option to determine if its composition is uniform throughout.

3. Eliminate options that are pure substances or heterogeneous mixtures.

Try solving on your own before revealing the answer!

Q9. The shape of the ammonia molecule (NH3) is ________.

Background

Topic: Molecular Geometry (VSEPR Theory)

This question tests your understanding of molecular shapes based on the number of bonding and lone pairs around the central atom.

Key Terms:

• VSEPR Theory: Valence Shell Electron Pair Repulsion theory, used to predict molecular shapes.

• Trigonal pyramidal: Shape with three bonds and one lone pair on the central atom.

Step-by-Step Guidance

1. Draw the Lewis structure for $\mathrm{NH_3}$.

2. Count the number of bonding pairs and lone pairs on the central atom (N).

3. Use VSEPR theory to determine the molecular geometry based on these pairs.

4. Match the geometry to the correct name among the options.

Try solving on your own before revealing the answer!

Q10. How many calories are required to increase the temperature of 13 g of ethanol from 11 °C to 23 °C? The specific heat of ethanol is 0.59 cal/g °C.

Background

Topic: Heat and Temperature Change

This question tests your ability to use the specific heat formula to calculate the heat required for a temperature change.

Key Formula:

• $q = m \times c \times \Delta T$

Where:

• $q$ = heat (calories)

• $m$ = mass (g)

• $c$ = specific heat (cal/g °C)

• $\Delta T$ = change in temperature ($T_{\!f} - T_{\!i}$)

Step-by-Step Guidance

1. Identify the given values: $m = 13\ \text{g}$, $c = 0.59\ \text{cal/g}^\circ\text{C}$, $T_{\!i} = 11^\circ\text{C}$, $T_{\!f} = 23^\circ\text{C}$.

2. Calculate the temperature change: $\Delta T = T_{\!f} - T_{\!i}$.

3. Plug the values into the formula: $q = m \times c \times \Delta T$.

4. Multiply the values stepwise, but stop before the final multiplication.

Try solving on your own before revealing the answer!

Final Answers

1) B) O2- 2) D) Al(NO3)3 3) B) 236 kcal 4) A) hydrogen bonds 5) A) This minimizes the harmful side effects of the radiation. 6) D) has a negative charge 7) A) 101.3 °F 8) C) eye drops 9) B) trigonal pyramidal 10) B) 92 cal

Each answer is based on the application of the concepts and formulas discussed above. Review the step-by-step guidance to reinforce your understanding!