General Chemistry Midterm Review: Reactions, Calculations, and Lab Procedures

Major component of Nature gas

Methane

Ternary acid H2SO4

sulfuric acid

Formula of sodium hydrogen carbonate

NaHCO3

Volume read from graduated cylinder

76.0 mL

Density of gold

19.3 g/cm3

Reason for using crucible tongs

To avoid contaminating the crucible and lid with the contaminants on the skin of the fingers and avoid burning the fingers.

Best way to cool crucible and lid

In a desiccator to minimize the probability of water being adsorbed onto the crucible and lid.

Preparation of Mg ribbon before reaction

To be polished

Molar mass of FeSO4

151.908 g/mol

Empirical formula of table salt

NaCl

Empirical formula of silver sulfide

Ag2S

Type of reaction A + B = AxBy

Combination Reaction

Limiting reactant

The reactant that determines how much product can be made

Correct statement about chemical reactions

A chemical reaction stops when the limiting reactant is used up

Moles of Mg needed to react with 12 mol of HCl

6 moles

Limiting reagent in gas mixture of H2 and O2

To be determined based on the reaction equation

Limiting Reagent

In the reaction 2H2(g) + O2(g) → 2H2O(g), the limiting reagent is O2.

Yield Percentage

In the experiment with 2 moles of H2 and 30 g of H2O generated, the yield percentage is 83.3%.

Purpose of Gravity Filtration

The purpose of gravity filtration is to separate precipitate from liquid solution.

Moles of Li3N Yielded

For the reaction 6 Li(s) + N2(g) → 2 Li3N(s), if 3 mol of Li(s) mixed with 1 mol of N2(g), 1 mol of Li3N(s) is yielded.

Color of Copper (II) Ion

The color of the copper (II) ion in solution is (B) sky blue.

Balanced Equation for Displacement

The balanced equation for the displacement of copper(II) ion from solution with magnesium metal is Cu2+(aq) + Mg(s) → Cu(s) + Mg2+(aq).

Reaction Type

The reaction 2NaOH (aq) + Cu(NO3)2(aq) → Cu(OH)2 (s) + 2 NaNO3(aq) is a Double displacement reaction.

Purpose of Centrifuge

The purpose of a centrifuge is to separate the two substances.

Percent Recovery of Copper

If a 0.0152 g sample of copper metal is recycled and 0.0076 g is recovered, the percent recovery of the copper metal is 50%.

Ions in K2CO3 and FeCl3

The ions present in a mixture of K2CO3 and FeCl3 before any reaction occurs are K+, CO32-, Fe3+, Cl-.

Law of Conservation of Mass

According to the Law of Conservation of Mass, when you burn a candle, the rest of the original candle's mass was changed to gases.

Type of Reaction

The reaction 4Si + S8 --> 2Si2S4 is a Combination reaction.

Spectator Ions

Spectator ions appear in the total ionic equation for a reaction, but not in the net ionic equation. (True)

Oxidizing Agent

If oxygen is an oxidizing agent in a reaction, the oxidation number of oxygen must be decreased.

Oxidizing and Reducing Agents

In the reaction Zn (s) + Fe2+ → Zn2+ + Fe (s), the reducing agent is Zn.

Redox Reaction

The reaction Mg (s) + CuCl2 (aq) → MgCl2 (aq) + Cu (s) is a Redox Reaction.

Oxidation Process

The chemical change Mg(s) → Mg2+ + 2e- is an Oxidation process.

Bunsen Burner

How to operate: The order to open valves and ignite.

Air-control valve

Color changes with/without sufficient air.

Cool flame

A flame produced with insufficient air.

Hot flame

A flame produced with sufficient air.

Density

D = M/V

Unknown solid measurement

How to measure volume of unknown solid and calculate density.

Density calculation effect

If the solid does not immerse into water completely, the recorded volume will be lower than the real volume.

Density calculation

Based on equation; D = M / V, the measured V ↓, therefore the calculated D ↑.

Unknown liquid density

How to calculate density and errors due to liquid evaporation.

Graduated cylinder

How to read volume using graduated cylinder.

Significant Figures

Follow Sig Fig rules to do calculation.

Combination Reaction

Reaction of Magnesium and Oxygen.

Chemical equation for Magnesium and Oxygen

2Mg + O2 → 2MgO

Molar Mass of Mg

24.32 g/mol

Molar Mass of O

16 g/mol

Crucible usage

How to use crucible when heating Mg.

Dry agent

Substance that causes color change.

Concept of Mole

Understand concept of Mole.

Empirical Formula calculation

Calculation from data as in Report sheet.

Mass percent calculation

Calculation from data as in Report sheet.

Balancing equations

How to balance the equation.

Excess Reactant

The reactant that is not completely consumed in a reaction.

Yield percentage calculation

Yield percentage = actual yield / theoretical yield * 100%

Theoretical yield

The maximum amount of product that can be formed from given amounts of reactants.

Example yield calculation

If 3 mol of Li(s) mixed with 1 mol of N2(g), how many mol of Li3N(s) yielded?

Balanced Equation

6 Li(s) + N2(g) → 2 Li3N(s)

Molar ratio

Li : N2 : Li3N = 6 : 1 : 2

Limiting Reactant (LR)

The reactant that is completely consumed in a reaction, determining the amount of product formed.

Excess Reactant (ER)

The reactant that remains after the limiting reactant is used up in a reaction.

Percent of Na2SO4 (LR)

Mass percent of Na2SO4 (LR) = 0.284g / 0.810 g X 100% = 35.1%

Percent of BaCl2•2H2O (ER)

Mass percent of BaCl2•2H2O (ER) = 0.526g / 0.810 g X 100% = 64.9%

Mole Calculation

The mole of BaSO4 is: Mass/Molar Mass = 0.00199 mol

Recovery Percent

A calculation to determine the efficiency of a reaction, often expressed as a percentage.

Reduction Process

The process that one substance gains electrons.

Reducing Agent

A substance that donates electrons in a redox reaction, causing another substance to be reduced.

Double Displacement Reaction

A type of reaction where two compounds exchange ions to form two new compounds.

Decomposition Reaction

A reaction where a single compound breaks down into two or more simpler products.

Molecular Equation

An equation that shows the complete chemical formulas of reactants and products.

Complete Ionic Equation

An equation that shows all of the ions present in a solution.

Net Ionic Equation

An equation that shows only the ions that participate in the reaction, excluding spectator ions.

Chemical Equations for Reactions

Cu → Cu(NO3)2 → Cu(OH)2 → CuO → CuSO4 → Cu

Molar Mass of BaCl2•2H2O

244.27 g/mol

Molar Mass of Na2SO4

142.04 g/mol

Molar Mass of BaSO4

233.39 g/mol