Chemistry Lab Final 3 Flashcards

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Questions and Answers

What is meant by the simplest formula of a compound?

The lowest whole number ratio of the atoms in the formula.

How does a hydrate differ from an anhydrate?

A hydrate is combined with a specific number of water molecules; an anhydrate is an ionic compound that remains when all water is removed.

What happens when a hydrate is heated?

The water will evaporate and water molecules are removed.

A hydrate of CoCl2 with a mass of 6.00 g is heated strongly. After cooling, the mass of the anhydrate is 3.27 g. How many grams of H2O were lost from the hydrate?

2.73 g H2O. Signup and view all the answers

What is the percentage of H2O in the hydrate?

45%. Signup and view all the answers

Write the equation for the dehydration of the CoCl2 hydrate.

6H2O + CoCl2 -(HEAT)-> CoCl2 + 6H2O. Signup and view all the answers

Using the rules for writing the formulas of ionic compounds, write the ions and the correct formula for magnesium.

MgO. Signup and view all the answers

Write a balanced equation for the reaction of magnesium and oxygen (O2), including their physical states.

2Mg + O2 -(HEAT)-> 2MgO. Signup and view all the answers

Using the formula obtained for MgSO4 hydrate, write a balanced equation for its dehydration.

MgSO4 + 7H2O -(HEAT)-> MgSO4 + 7H2O. Signup and view all the answers

In making pickles, a cucumber is placed in a concentrated salt solution. Explain what happens to the cucumber when it is left in the salt solution for some time.

The cucumber is placed in a hypertonic solution and the water is drawn out of the cucumber through osmosis. Signup and view all the answers

Why is it important that cell membranes are semipermeable?

Because nutrients can be brought into a cell. Signup and view all the answers

What are the differences between solutions, colloids, and suspensions?

Solutions are filtered out by semipermeable membranes; colloids are smaller and cannot be filtered out by filter paper; suspensions are larger and cannot be filtered out by filter paper. Signup and view all the answers

What is the result of a 10% (m/v) starch solution?

a. Signup and view all the answers

What is the result of a 2% (m/v) albumin solution?

b. Signup and view all the answers

What is the result of an 8% (m/v) sucrose solution?

a. Signup and view all the answers

What is crenation?

10% (m/v) NaCl. Signup and view all the answers

What is hemolysis?

2% (m/v) glucose. Signup and view all the answers

What happens to cells in a solution with a pH of 12.0?

Basic. Signup and view all the answers

What happens to cells in a solution with a pH of 2.0?

Acidic. Signup and view all the answers

What is a buffer?

Maintains the pH of a solution by reacting with and neutralizing small amounts of acids and bases. Signup and view all the answers

If you add acid or base to water, how will the pH change?

pH will change between 7-14; it will raise the pH if acid is added. Signup and view all the answers

If you add acid or base to a buffer, how will the pH change?

pH will not change. Signup and view all the answers

Which solutions showed the greatest change in pH? Why?

H2O, 0.1 M NaCl. Signup and view all the answers

Which solutions showed little or no change in pH? Why?

High/low buffer. Signup and view all the answers

What is neutralization?

The reaction of H+ ions from the acid combine with OH- from a base to produce salt and water. Signup and view all the answers

Write an equation for the neutralization of H2SO4 by KOH.

H2SO4 (aq) + 2 KOH (aq) ---> K2SO4 + 2H2O. Signup and view all the answers

What is titration?

Addition of a specific amount of base required to neutralize acid in a sample. Signup and view all the answers

What is the function of an indicator in a titration?

It changes color and determines the endpoint, which indicates if acid has been neutralized by the addition of base. Signup and view all the answers

Study Notes

Compound Formulas

Simplest formula: lowest whole number ratio of atoms in a compound.

Hydrates and Anhydrates

Hydrate: ionic compound combined with a specific number of water molecules.
Anhydrate: removes water, leaving a pure ionic compound.

Heating Hydrates

Heating causes water in hydrates to evaporate, resulting in the removal of water molecules.

Mass Loss Calculations

To find mass of water lost from a hydrate, subtract anhydrate mass from hydrate mass.
Example: 6.00g hydrate - 3.27g anhydrate = 2.73g H2O lost.

Percentage of Water in Hydrate

Calculate % water in hydrate using: (mass of H2O / mass of hydrate) x 100.
Example: (2.73g / 6.00g) x 100 = 45%.

Chemical Equations

Dehydration of CoCl2 hydrate:
- 6H2O + CoCl2 -(HEAT)-> CoCl2 + 6H2O.
Balanced equation for Mg with O2:
- 2Mg + O2 -(HEAT)-> 2MgO.
Dehydration of MgSO4 hydrate:
- MgSO4 + 7H2O -(HEAT)-> MgSO4 + 7H2O.

Osmosis and Cell Membranes

Cucumber in concentrated salt solution: placement in hypertonic solution draws water out via osmosis.
Semipermeable cell membranes allow nutrient intake.

Mixtures and Solutions

Solutions can be filtered out by semipermeable membranes.
Colloids consist of smaller particles that cannot be filtered by filter paper.
Suspensions contain larger particles also unable to be filtered by paper.

Concentration Differences

Higher concentration solutions yield greater osmotic effects; examples include various concentrations of starch and glucose.

Effects of Solutions on Cells

Hypertonic solutions cause crenation; hypotonic solutions lead to hemolysis.
Isotonic solutions exhibit no change in cell shape.

Indicators and Reactions

Benedict's reagent turns orange-red for glucose; iodine turns blue-black for starch; AgNO3 forms white precipitate with chloride.
Dialysis bag experiments reveal molecules like glucose and Cl- crossing semipermeable membrane.

Gas Laws and Pressure

Combined gas law: P1V1/T1 = P2V2/T2; rearranged gives V2 = V1P1T2/P2T1.
Distinction between vapor pressure (pressure of vapor over liquid) and atmospheric pressure (force exerted by atmosphere).

Standard Conditions

Standard temperature and pressure (STP): 0°C (273K) and 1 atm (760 mmHg).
Molar volume of a gas at STP is 22.4 L/mol.

pH and Solutions

pH is closely related to [H3O+]: pH = -log[H3O+].
Adding an acid to water raises [H+] and lowers pH; adding a base raises the pH.

Buffer Systems

Buffers stabilize pH by neutralizing excess acids or bases—maintaining equilibrium.
Blood pH between 7.35 and 7.45 managed by bicarbonate buffer system.

Neutralization Reactions

Neutralization involves H+ ions from an acid and OH- from a base forming salt and water.
Example reaction: H2SO4 + 2 KOH → K2SO4 + 2 H2O.

Titration Process

Titration determines the amount of base needed to neutralize an acid using indicators for endpoint detection.

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Description

Test your knowledge with this set of flashcards designed for Chemistry Lab Final 3. Each card challenges you to define key concepts about compounds, hydrates, and their properties. Perfect for revision before your final exam!