Chem Exam 3 part 1

How many moles of butane are in 40.0 g of butane (C4H10)? Molar mass = 58.12 g/mol

0.688mol C₄H₁₀

Mass Calculations for Reactions

1) Write a balanced chemical equation; calculate molar masses of relevant species. 2) Use the given molar mass to calculate moles given. 3) Use rxn mole ratio to convert moles given to wanted. 4) Use the final molar mass to calculate grams wanted.

Calculate the number of moles in 6.96 x 10^24 sodium atoms.

11.6 mol Na

In a reaction of aluminum with iron(III) oxide, how many moles of aluminum are required to react with 7.0 moles of iron(III) oxide? 2 Al(s) + Fe₂O₃ → Al₂O₃(s)+2 Fe(s)

14 mol Al

Consider the following equation: 3H₂(g) + N₂(g) →2NH₃(g) A mole-mole factor for H2 and N2 is A mole-mole factor for NH3 and H2 is

1mole N₂/3 moles H₂ 2 moles NH₃/3 moles H₂

Balancing the chemical equation C₄H₁₀ +O₂→ CO₂ + H₂O H₂SO₄ + Al(OH₃)→ Al₂ (SO₄)₃+ H-OH H₂O + CO₂→ C₆H₁₂O₆ +O₂

2 C₄H₁₀+13 O₂ → 8 CO₂ +10 H₂O 3 H₂SO₄ +2 Al(OH₃)→ Al₂ (SO₄)₃+6 H-OH 6 H₂O+ 6 CO₂→C₆H₁₂O₆+ 6 O₂

Balancing the chemical equation Na + H₂O → H₂ + NaOH

2Na + 2H₂O → H₂ + 2NaOH

How many atoms are in 0.818 moles of potassium?

4.92 x 10²³ K atoms

How many grams of silver can be made from the reaction of 13.4g of copper with an excess of silver nitrate?, Cu+2 AgNo3 -> Cu(NO3)2 + 2Ag Molar masses : Ag 107.9 g/mol : Cu 63.55 g/mol

45.5g Ag

How many grams of Fe can be produced from the reaction of 24.6 g Al and an excess of iron(III) oxide? Molar masses : Fe 55.85 g/mol ; Al 26.98 g/mol 2 Al(s) + Fe₂O₃ → Al₂O₃(s) + 2 Fe(s)

50.9g Fe

How many grams of NaCl are in 11.1 moles of NaCl? Molar mass = 58.44 g/mol

649gNaCl

Consider the following problem: One of the fuels sold as "bottled gas" is butane, C₄H₁₀. Calculate the energy that may be obtained by burning 1.50 kg of butane if ∆H = - 5.77 x 10^3 kJ for this reaction. Is this reaction endothermic or exothermic? Molar mass of C₄H₁₀ is 58.12 g/mol 2 C₄H₁₀(g) + 13O₂(g) → 8 CO₂(g) + 10 H₂O(l)

7.45 x 10⁴

How many moles of oxygen are required, and how many moles of carbon dioxide are produced, when 11.1 moles of butane are burned? 2C₄H₁₀+13 O₂→ 10H₂O+8 CO₂

72.2 mol O₂ 44.4 mol Co2

A chemical reaction is expected to produce 9.82 g product, but only produces 8.13 g product. What is the percent yield?

82.8%

How many gold atoms are in one troy ounce (31.10 g) of gold? Molar mass = 197.0 g/mol

9.50 x 10²² Au atoms

Combination Reactionn

A reaction in which two or more substances combine to form a single product is a combination reaction. A + X → AX Examples: H₂(g) + Cl₂(g) → 2 HCl(g)

Identify each of the following as oxidation or reduction: A. Sn(s) → Sn⁴+(aq) + 4e− B. Fe³+(aq) + 1e− → Fe²+(aq) C. Cl₂(g) + 2e− → 2Cl− (aq)

A. Oxidized B. reduction C. reduction

Which is reduced and which is oxidize Cl₂ +2KI → 2KCl + I₂

Cl is reduced I is oxidized

Name the reaction type Ca+Cl₂→CaCl₂ Fe₂S₃→2Fe+3S Cu+2AgNO₃→Cu(NO₃)₂+2Ag BaCl₂+K₂SO₄→BaSO₄+2KCl CH₄+2O₂→CO₂+2H₂O+energy

Combination Decomposition Single Replacement Double Replacement Combusion

Write the equation for the complete oxidation of butanol, C₄H₉OH(l).

C₄H₉OH+O₂→CO₂+H₂O Balanced Form C₄H₉OH+6O₂→4CO₂+5H₂O

Double Replacement Precipitation Reactions

Definition: The recombination of ionic compounds from solutions to form different ionic species, one or more of which are insoluble. The insoluble species is called a precipitate. Equation (general form): AB(aq) + CD(aq) → AD(aq) + BC(s) (A,C are cations, BD are anions) Example: The precipitation of silver chloride from solutions of sodium chloride and silver nitrate: NaCl(aq) + AgNO₃(aq) → NaNO₃(aq) + AgCl(s)

Single-Replacement Oxidation Reduction (Redox) Reaction

General equation for single-replacement reaction: A + BX → AX + B A single replacement reaction is a reaction in which one element takes the place of another similar element as part of a compound. Mg(s) + NiSO₄(aq) → MgSO₄(aq) + Ni(s)

Decomposition Reaction examples HI→ Lithium combines with oxygen to form lithium oxide

H₂ + I₂ Li + O₂→ 2Li₂O

Combination Reactions (Find the product) H₂ +O₂→ 2 H₂ +O₂→ Mg + O₂→ 2C + O₂→

H₂O 2H₂O 2MgO 2CO

Combustion Reactions

In a combustion reaction, a carbon-containing compound burns in oxygen gas to form carbon dioxide (CO2) and water (H2O). energy is released as a product in the form of heat. CH₄(g) + 2O₂(g)→ CO₂(g) + 2H₂O(g) + energy C3H8(g) + 5O2(g)→ 3CO₂(g) + 4H₂O(g) + energy

A precipitate forms when solutions of potassium hydroxide, KOH and aluminum nitrate, Al(NO₃)₃ are combined. Write the equation.

KOH+Al(NO₃)₃→KNO₃+Al(OH)₃ Balanced Form 3KOH+Al(NO₃)₃→3KNO₃+Al(OH)₃

Redox pt.

Mg(s) + NiSO₄(aq) → MgSO₄(aq) + Ni(s) In the previous example Mg was oxidized and Ni was reduced. Mg(s) → Mg²⁺(aq) + 2e- Ni²⁺(aq) + 2e- → Ni(s)

Decomposition Reactions

One reactant forming two or more products Simply put, a decomposition reaction is the opposite of a combination reaction. AX → A + X Examples: 2H₂O(l) → 2H₂(g) + O₂(g)

Oxidation Reduction Reaction

Reduction: gain electrons Oxidation: lose electrons ex. 2 AgNO₃(aq) + Cu(s) → Cu(NO3)₂ + 2 Ag(s) The Ag+ is being reduced to Ag: The Cu(s) is being oxidized to Cu²+

Enthalpy:

The energy change or heat change in a chemical reaction is measured by the heat of reaction or enthalpy of reaction: ∆H. Enthalpy can be either heat evolved or heat absorbed. ∆H = H(products) - H(reactants)

The mole

The mole is a quantity. One mole is the number of atoms in 12 g of 12C. One mole is 6.022 x 10^23 'things' 6.022 x 10^23 mol-1 is Avogadro's number. 1 mole of O2 is 6.022 x 10^23 O2 molecules 1 mole of MgCl2 has 6.022 x 10^23 formula units of MgCl2. Use Avogadro's number to convert between moles, and molecules or atoms.

Molar Mass

To express chemical quantities at the macroscopic level chemists work in terms of molar mass. Molar mass is the mass in grams of one mole of a substance. The units of molar mass are grams per mol or mathematically g / mol (Located on the periodic table)

Percent Yield =

actual yield/theoretical yield times 100%

Organic chemistry

dedicated to compounds containing mainly C,H and O. Compounds like this are burned in air they react with oxygen in the atmosphere, this is called oxidation or oxidized. The product of a complete burning or oxidation are always the came CO₂ and H₂O

In an endothermic reaction,

heat is absorbed. the energy of the products is greater than the energy of the reactants. heat is a reactant (added). N₂(g) + O₂(g) + 180 kJ →2NO(g) ΔH = +180 kJ

In an exothermic reaction,

heat is released. the energy of the products is less than the energy of the reactants. heat is a product. H₂(g) + Cl₂(g) → 2HCl(g) + 185 kJ ΔH = −185 kJ

Percent Yield Theoretical yield: Actual Yield:

is the actual amount of product a reaction produces. The amount of product a reaction produces assuming the reaction uses all reactants. The 'real life' amount of product formed in a reaction.

The molar mass or formula mass is the sum of the elemental molar masses in a compound. Calculate the molar mass of potassium chloride barium phosphate

potassium chloride: 74.55g/mol Barium Phosphate: 601.8g/mol

∆H negative ∆H positive

the reaction gives off heat (exothermic):burning gasoline reaction absorbs heat (endothermic) a sports 'icepack' cools

Consider the following reaction C₇H₁₆ + 11 O₂ → 7 CO₂ + 8 H₂O Calculate the theoretical yield and the percentage yield of CO₂ if 66.0 g of C₇H₁₆ yields 182 g of CO₂. (Molar Masses: C₇H₁₆ 100.20 g/mol, CO₂ 44.01 g/mol)

theorectical yield = 203g CO₂ Percent Yield= 89.7%