General Chemistry PHARM-101: Stoichiometry Quiz

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Questions and Answers

What is the primary function of stoichiometry in chemical reactions?

To measure the energy changes during reactions

To determine the color of reactants involved

To identify unknown substances in a mixture

To calculate the quantities of reactants and products (correct)

In the combustion of octane, what is the stoichiometric ratio of moles of C8H18 to moles of CO2 produced?

16:2

25:16

2:16 (correct)

2:18

What defines a concentrated solution compared to a dilute solution?

Faster reaction rate of solutes

Presence of more solvent than solute

Higher temperature of the solution

Larger proportion of solute to solvent (correct)

How are the coefficients in a balanced chemical equation significant to stoichiometry?

They specify the relative amounts in moles of reactants and products Signup and view all the answers

When given 22 moles of C8H18, how many moles of CO2 can be predicted to be produced using stoichiometry?

176 moles Signup and view all the answers

What is the correct formula to calculate molarity (M) of a solution?

M = weight (g) / molecular weight × volume (L) Signup and view all the answers

Which of the following correctly describes the unit of molarity?

Moles of solute per liter of solution (mol/L) Signup and view all the answers

In the context of molarity, if 25.5 g of KBr is dissolved in 1.75 L of solution, what is the first step needed to find the molarity?

Convert 25.5 g of KBr into moles. Signup and view all the answers

If a solution has a molarity of 0.125 M and contains 0.255 mol of NaOH, how would you calculate the volume of the solution?

Volume (L) = moles of solute / molarity Signup and view all the answers

Which concentration unit uses grams of solute per 1000 grams of solvent?

Molality Signup and view all the answers

Which of the following substances is classified as a strong electrolyte?

Hydrochloric acid (HCl) Signup and view all the answers

What distinguishes weak electrolytes from nonelectrolytes?

Weak electrolytes partially ionize while nonelectrolytes do not ionize at all. Signup and view all the answers

Which of the following compounds is a weak acid?

Hydrofluoric acid (HF) Signup and view all the answers

In which type of reaction do two or more reactants combine to form a single product?

Synthesis Reaction Signup and view all the answers

Which of the following statements about nonelectrolytes is true?

Nonelectrolytes include molecular substances like sugar and alcohol. Signup and view all the answers

What type of reaction is demonstrated by the equation 2 H2O ⟶ 2 H2 + O2?

Decomposition reaction Signup and view all the answers

In a double replacement reaction, what is expected to occur?

The anions and cations of two compounds switch places Signup and view all the answers

What happens during a single replacement reaction?

One element replaces another element in a compound Signup and view all the answers

Which equation represents a synthesis reaction?

2 H2 + O2 ⟶ 2 H2O Signup and view all the answers

What would result from mixing a metallic hydroxide with an acid according to the information provided?

Formation of water Signup and view all the answers

Study Notes

General Chemistry for Pharmaceutical Sciences (PHARM-101)

Course presented by Dr. Azza H. Rageh, Associate Professor of Pharmaceutical Analytical Chemistry at Taibah University
Course covers Stoichiometry, Solution Concentration, and Chemical Reactions.

Stoichiometry

Stoichiometry involves calculating the amounts of reactants and products in a chemical reaction
It allows predicting product amounts based on reactant amounts
It determines the necessary reactants to create a specific amount of product.
Coefficients in balanced chemical equations represent relative mole amounts of substances.

Reaction Stoichiometry

Example: 2 C₈H₁₈(l) + 25 O₂(g) → 16 CO₂(g) + 18 H₂O(g)
- 2 moles of C₈H₁₈ react with 25 moles of O₂ to form 16 moles of CO₂ and 18 moles of H₂O.
This example demonstrates the stoichiometric ratio between reactants and products. Stoichiometric ratios are used to calculate product amounts (or needed quantities of reactants).

Concentration of Solutions

Concentration measures the amount of solute in a solution
Units for concentration include percentage by weight, percentage by volume, parts per million, parts per billion, molarity, formality, normality and molality.
Molarity (M) is a measure of concentration.
- Molarity (M) = moles of solute / liters of solution

Molarity Calculations

Example 1: Find the molarity of a solution with 25.5 g KBr dissolved in 1.75 L of solution.
- Molarity (M) = 0.122 M
Example 2: Calculate the liters of 0.125 M NaOH solution containing 0.255 mol NaOH.
- Liters (L) = 2.04 L

Types of Aqueous Solutions and Solubility

Familiar examples include salt water (NaCl & H₂O) and sugar water (C₁₂H₂₂O₁₁ & H₂O).
These solutions are homogeneous mixtures.
Solids like salt and sugar dissolve in water because of attractive forces between solute and solvent particles.

Dissolving of Ionic Compounds

Each ion in the compound is attracted to surrounding water molecules.
The water molecules pull the ions away from the crystal

Dissolving of Molecular Compounds

Molecules of the compound mix homogeneously with water molecules.

Electrolytes and Nonelectrolytes

Electrolytes dissolve in water to form solutions that conduct electricity (ions formed).
Nonelectrolytes do not form ions when dissolved in water.
- Strong Electrolytes: completely ionize
- Weak Electrolytes: partially ionize

Types of Chemical Reactions (A Summary)

Synthesis, Decomposition, Single Replacement, Double Replacement

Basic Types of Chemical Reactions

Synthesis: Two or more reactants combine to form one product. (A + B → AB)
Decomposition: A complex substance breaks down into simpler substances. (AB → A + B)
Replacement (Single): One element replaces another in a compound. (A + BC → AC + B)
Replacement (Double): The cations and anions of two ionic compounds switch places. (AB + CD → AD + CB)

Chemical Reactions Between Ions

Ions react through water formation, weak electrolytes, precipitates, gases, and complex ion formation

Formation of Water: Acid-Base Reactions

Metal hydroxides (including ammonium hydroxide) react with acids to form water.
- Example: NaOH + HCl → NaCl + H₂O

Formation of Weak Electrolytes

A strong acid with a salt that contains the anion of a weak acid forms the weak acid.
Example: HCl + CH₃COONa → NaCl + CH₃COOH (weak acid)

Formation of a Precipitate

Precipitation occurs when the concentration of dissolved ions exceeds the solubility limit forming an insoluble salt in a solution. Precipitate is solid.
Example: AgNO₃ + NaCl → AgCl_(s) + NaNO₃

Formation of Gas

Formation of a gas results from the product being gaseous or the product decomposing to form gas.
Example: 2H⁺ + S^2- → H₂S_(g) -Example: Acid forms unstable acids (H₂CO₃, H₂SO₃, H₂S₂O₃, HNO₂)

Formation of Complex Ions

A complexation reaction involves a Lewis acid (metal) and a Lewis base (ligand).
Ligands form coordinate bonds to the metal to form a complex.
Example: Cu²⁺ + 4 NH₃ → [Cu(NH₃)₄]²⁺

Reactions Involving Oxidation-Reduction (Redox)

Redox reactions involve electron transfer.
Oxidation is a loss of electrons, reduction is a gain of electrons.
Oxidation and reduction reactions must always occur together.
Example: 2 Na(s) + Cl₂(g) → 2 NaCl(s)

Oxidizing and Reducing Agents

Oxidizing agent (oxidant) causes oxidation, and is reduced itself.
Reducing agent (reductant) causes reduction and is oxidized itself.
Example: 2C₈H₁₈(l) + 25 O₂(g) → 16CO₂(g) + 18 H₂O(g)

Assessment Questions

Various assessment questions are provided related to the topics covered, including identifying products of reactions, classifying reaction types, calculating oxidation numbers, identifying oxidizing and reducing agents, and defining chemical reactions.

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Description

Test your knowledge of stoichiometry as it applies to chemical reactions in the context of pharmaceutical sciences. This quiz covers the calculation of reactants and products, as well as the interpretation of balanced chemical equations. Prepare to apply your understanding of chemical relationships in practical scenarios.