CHM 101 Lecture Notes - Lecture 3: Limiting Reagent, Empirical Formula, Chemical Formula

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17 Sep 2017

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Chapter 3: stoichiometry: calculations with chemical formulas and equations. Balanced chemical equation gives qualitative and quantitative information tells what is reacting, what is forming and the relative amounts of each. 2h2 + o2 2 h2o + heat. Very important: make sure you have correct formulas for reactants and products before you try to balance the equation use of balanced equation on microscopic level carbon completely reacting with oxygen. Ch4 + 2o2 co2 + 2h2o + heat. C3h6 + 9/2o2 3co2 + 3h2o *fractions are improper* Ch3oh +3/2 o2 co2 + 2h2o *fractions are improper* 2ch3oh + 3o2 2co2 + 4h2o + heat metal and nonmetal react to form an ionic compound (a salt) and heat example of a combination reaction. 2 mg(s) + o2(g) 2 mgo + heat. Salts are solids at room temperature decomposition of metal carbonates - to form metal oxide and co2. Back to c and o2 example review microscopic.

Related Questions

1. Determine the amount of solute in the following samples:

500 ml of 0.2 M KI (potassium iodide)

220 ml of 0.03 M H2SO4 (sulfuric acid)

2.5 l of 0.1 M MgNO3 (magnesium nitrate)

1 ml of 5 M HCl (hydrochloric acid)

This problem requires that you know what molarity (M) is. M (molarity) = # of moles of solutes / Liter of solution. You are given the volume. You should be able to obtain moles of solutes. Your answers can be in moles or grams (either one will be acceptable).

2. How many ml of 0.1 M HCl would be required to titrate 35 ml of 1 M NaOH to the end point?

This is an acid/base reaction.

1) First, write out the balanced chemical reaction for HCl + NaOH.

2) Second, figure out the number of moles of NaOH in 35 ml of 1 M NaOH.

3) How many moles of HCl is required for completely reacting with the moles of NaOH in Part 2).

3. What is the pH of a 0.03 M solution of the strong base NaOH?

1) This question requires that you know pH = - log [H₃O⁺], or simply as pH = - log [H⁺] (to make it easier).

2)So, you have to know how to use your scientific calculator to do log function (check Youtube).

3) This question also requires that you know: pOH = - log [OH^-].

4) This question also requires that you know: [H₃O⁺][OH^-] = 1.0 x 10^-14 or pH + pOH = 14

5) First step, determine the concentration of OH^- in 0.03M NaOH when it dissociates or breaks up into Na⁺ and OH^-.

6) This will give you [OH^-]. You can plug this into pOH = - log [OH^-] to get pOH.

7) Once you get pOH, then use (pH + pOH = 14) to get pH.

4. Balance the chemical reactions shown below and then write equilibrium expressions for each. All reactants and all products are in the gas phase.

CO + F₂ ------> COF₂

CH₄ + O₂ ------> CO₂ + H₂O

N₂O₄ -----> Br₂ + NO

BrNO -----> Br₂ + NO

1)This problem requires that you know how to balance chemical equations.

2)After you balance the equation, you need to know the equilibrium expression

5. Determine the oxidation states of each element comprising the following ionic compounds:

KClO₄

NaMnO₄

Sr(NO₃)₂

NaHCO₃

CH₄

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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CHM 101 Lecture Notes - Lecture 3: Limiting Reagent, Empirical Formula, Chemical Formula

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