CH 110 Lecture Notes - Lecture 3: Chemical Formula, Reagent, Aqueous Solution

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coralbear227

6 Jan 2017

School

University of Hartford

Department

Chemistry - A&S

Course

CH 110

Professor

Krause Tatum

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Law of conservation of mass- mass is neither destroyed nor created. 2h2 (g) + o2 (aq) 2h2o (l) Ch4 (g) + 2o2 (g) co2 (g) + h2o (g) States of the reactants and products are written in parenthesis to the right of each compound. (g) gass, (s) solid, (l) liquid), (aq) in aqueous solution. Subscripts in the formula- give the ratio in which the atoms are found in the molecule. Stoichiometric coefficients- give the ratio in which the products and reactants exist. Are inserted to balance the equation to follow the law of conservation of mass. Write the skeleton equation in which the formulas of the reactants appear on the left and those of the products on the write. Indicate the physical state of each reactant and product, after the formula by writing the states of the reactants and products. Count number of atoms of each reactant and the number of atoms of each product.

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Chemical Reactions and Equations Learning objectives To observe physical and chemical properties associated with chemical changes To be able to give evidence for the occurrence of a chemical reaction To write a balanced chemical equation To identify areaction as a combination, decomposition, precipitation, single or double replacement, or combustion reaction ntroduction When a substance undergoes a physical change, it changes its appearance but not its composition. For example, when ice melts to form water, it undergoes a physical change from solid to liquid. In a chemical change, the composition of a substance is changed to give a new substance with different physical and chemical properties. For example, when silver tarnishes, the shiny silver (Ag) changes to a dull gray silver sulfide (AgaS). Not only has the chemical formula changed from Ag to Agus, but also the physical properties (shininess) of the substance have changed. Some examples of physical and chemical changes are listed in Table 1 below. Table 1. Comparison of Physical and Chemical Changes Examples of Physical changes Examples and Evidence of Chemical Changes Change in state (melting, freezing, evaporating Formation of a gas (bubbles) subliming) Formation of a solid (precipitate) Change in size Tearing Change in Color Heat is given off or absorbed A solid dissolving in a solvent In a chemical reaction, atoms in the reactants are rearranged to produce new combinations of atoms in the products. However, the total number of atoms of each element in the reactants is equal to the total number of atoms in the products. This is true according to the Law of Conservation of Mass, which states that the total mass remains constant during a chemical reaction. In other words, matter cannot be created or destroyed in a chemical reaction. In a chemical equation, the reactants are shown on the left and the products are on the right. An arrow in between indicates that a chemical reaction occurs. Finally, the physical state of each compound is designated in parentheses after the chemical formula. Solid, liquid, gas, and aqueous (dissolved in water) are shown as(s,(n,(g), and (aq), respectively.

Having trouble with thse questions. Please answer all questions correctly. Will provide a thumbs up.

1.Which of these equations is the balanced reaction between nitrous acid solution and solidmagnesium hydroxide ?

A.2NH₃(aq) + MgOH (s) Mg(NH₄)₂(aq) + 2 H₂O(l)

B.2HNO₂(aq) + Mg(OH)₂(s) Mg(NO₂)₂(aq) + 2 H₂O(l)

C.2HNO₃(aq) + Mg(OH)₂(s) Mg(NO₃)₂(aq) + 2 H₂O(l)

D.2HNO₂(aq) + MgOH (s) Mg(NO₃)₂(s) + 2H₂O(l)

2.Balance the following chemical equation:

C₃H₇OH(l) + O₂(g)CO₂(g) + H₂O(g)

a. C₃H₇OH(l) + 4 O₂(g)3 CO₂(g) + 4 H₂O(g)

b.2 C₃H₇OH(l) + 9 O₂(g)6 CO₂(g) + 8 H₂O(g)

c.C₃H₇OH(l) + 5 O₂(g)3 CO₂(g) + 4 H₂O(g)

d.C₃H₇OH(l) + O₂(g)CO₂(g) + H₂O(g)

3.Which species would be considered a spectator ion based on the following equation?

Ba²⁺ + 2NO₃^â + 2Na⁺ + SO₄^2- â BaSO₄(s) + 2NO₃^â + 2Na⁺

SO₄^2-

2NO₃^â

Ba²⁺

BaSO₄

4.Barium sulfate is often ingested to aid in the diagnosis of GI tract disorders. The equation for its production is Ba²⁺ + SO₄^2- â BaSO₄(s). What type of equation is this?

A full equation

A net ionic equation

A total ionic equation

An oxidation-reduction equation

5.Which species is being reduced in this reaction?

CuO(s) + H₂(g) Cu(s) + H₂O(g)

H₂O

CuO

H₂

6.Which of the following is an oxidizing agent?

H₂

NH₃

O₂

H₂O

7.The following chemical equation,

HC₂H₃O₂(aq) + KOH(aq) KC₂H₃O₂(aq) + H₂O(l),

is an example of a(n) _______ reaction.

a.oxidation-reduction and acid-base

b.acid-base

c.precipitation

d.oxidation-reduction and precipitation

e.oxidation-reduction

8.What substance is oxidized in the following reaction?

4HCl + MnO₂ â Cl₂ + 2H₂O + MnCl₂

a.Mn in MnO₂

b.O in MnO₂

c.Cl in HCl

d.H in HCl

9.What is the reducing agent in the following reaction?

4HCl + MnO₂ â Cl₂ + 2H₂O + MnCl₂

Cl₂

MnCl₂

HCl

MnO₂

10.All redox reactions involve oxygen.

True

False

11.The term formula weight can be used with respect to which of the following?

A.ionic compounds

B.covalent compounds

C.both a and b

D.neither a nor b

12.What is the molecular weight of ibuprofen, C₁₃H₁₈O₂?

A.206.3 amu

B.377.7 amu

C.29.0 amu

D.289.4 amu

13.The mass of an atom of ¹²C is exactly 12 atomic mass units. Which of the following describes a mole of ¹²C atoms?

A.a sample which weighs exactly 12 atomic mass units

B.a sample which contains 6.02 Ã 10²³ atoms of ¹²C

C.both a and b

D.neither a nor b

14.The mass of an atom of ¹²C is exactly 12 atomic mass units. Which of the following describes a mole of ¹²C atoms?

A.a sample which contains 6.02 Ã 10²³ atoms of ¹²C

B.a sample which weighs exactly 12.011 grams

C.both a and b

D.neither a nor b

15.What is the molar mass of water, H₂O?

A.18.02 g

B.18.02 amu

C.17.01 g

D.17.01 amu

16.What is the molar mass of glucose, C₆H₁₂O₆?

A.180.2 amu

B.180.2 g

C.60.05 amu

D.60.05 g

17.In the reaction 2H₂O â 2H₂ + O₂, 2.0 mol water will produce how many grams of O₂?

18.In the reaction 2CH₄ + O₂ â 2CO + 4H₂, how many molecules of CO will be produced by the complete reaction of 1.60 grams of CH₄?

3.01 Ã 10²²

2.00

12.0 Ã 10²³

6.02 Ã 10²²

19.Suppose 2.43 g of magnesium is reacted with 3.20 g of oxygen: 2Mg + O₂ â 2MgO. How many grams of MgO will be produced?

1.27

4.03

5.63

8.06

20.Which of the following conversion factors would allow one to calculate the amount of PbI₂produced from a given amount of NaI in the following unbalanced reaction?

Pb(NO₃)₂ + Nal â Pbl₂ + NaNO₃

21.The unbalanced equation for the reduction of copper(I) sulfide with oxygen is given below. What mass of copper is produced from the reduction of 7.50 g Cu₂S?

Cu₂S(s) + O₂(g) Cu(s) + SO₂(g)

18.8 g

5.99 g

1.50 g

9.39 g

2.99 g

22.How many grams of aluminum oxide are produced by the complete reaction of 19.8 g aluminum with excess oxygen?

10.5 g aluminum oxide

37.4 g aluminum oxide

49.9 g aluminum oxide

74.8 g aluminum oxide

23.If 5 grams of CO and 5 grams of O₂ are combined according to the reaction, which is the limiting reagent?

2CO + O₂ â 2CO₂

O₂

CO and O₂

CO₂

24.In an industrial process, nitrogen is reacted with hydrogen to produce ammonia. The percent yield of this particular process is 26%. How much hydrogen is needed to produce 4.8 kg ammonia?

1.5 kg

7.0 kg

0.85 kg

3.3 kg

25.A percentage yield greater than 100% has been reported in a scientific paper you are assigned to read. What would be a reasonable explanation for this?

a. The product was measured more than once.

b. It must be a typographical error since yields can't exceed 100%.

c. A lack of training of the professor who published the study.

d. Small measurement errors could have caused this to occur.

26.In an industrial process, nitrogen is reacted with hydrogen to produce ammonia. The percent yield of this particular process is 24.8%. How much hydrogen is needed to produce 3.7 kg ammonia?

1.8 kg

1.2 kg

4.4 kg

12 kg

2.7 kg

27.The following reaction has a percent yield of 90.5%. How many grams of carbon dioxide are produced from 78.5 g calcium carbonate via this reaction?

2 HNO₃(aq) + CaCO₃(aq) Ca(NO₃)₂(aq) + H₂O(l) + CO₂(g)

34.5 g

21.6 g

38.1 g

31.2 g

28.When gas molecules dissolve in liquids to form a saturated system, the process is usually

exothermic.

endothermic.

independent of the nature of the liquid.

temperature independent.

29.The reaction below would be considered.

CaCO₃ + heat â CaO + CO₂

an exothermic combination.

an exothermic decomposition.

an endothermic combination.

an endothermic decomposition.

30.The combustion of one mole of propane, C₃H₈, releases 531 kcal. How much heat is released by the combustion of 1.20 moles of propane?

A.584 kcal

B.690 kcal

C.443 kcal

D.637 kcal

31.The combustion of one mole of propane, C₃H₈, releases 531 kcal. How much heat is released by the combustion of 4.40 g of propane?

A.531 kcal

B.5.31 Ã 10⁴ kcal

C.53.1 kcal

D.5.31 Ã 10³ kcal

32.Metabolism of one mole of glucose, C₆H₁₂O₆, releases 670 kcal. How much heat is released by the combustion of 0.300 moles of glucose?

A.201 kcal

B.2.41 Ã 10³ kcal

C.186 kcal

D.2.23 Ã 10³ kcal

33.Metabolism of one mole of glucose, C₆H₁₂O₆, releases 6.70 Ã 10² kcal. How much heat is released by the combustion of 50.0 g of glucose?

A.201 kcal

B.2.41 Ã 10³ kcal

C.186 kcal

D.2.23 Ã 10³ kcal

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CH 110 Lecture Notes - Lecture 3: Chemical Formula, Reagent, Aqueous Solution

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