Balancing Synthesis and Decomposition reactions



Review for Unit 5 and 6 Exam

Due: February 8th/9th (before exam begins)

1. Describe what happens in a synthesis reaction.

2. Balance the following synthesis reactions, each time showing that mass was conserved.

a. Chemical equation: ____Mg (s) + ____O2 (g) ( ____MgO (s)

Molecular weight: _________g + ________g = _________g

3. Describe what happens in a decomposition reaction.

4. Balance the following decomposition reactions, each time ensuring that the law of conservation of mass applies.

a. Chemical equation: ____HgO (s) ( ____Hg (l) + ____O2 (g)

Molecular weight: __________g = ________g + ________g

5. Balance the following equations and label them as either a synthesis or decomposition reaction.

a. ____ Ba(OH)2 ( ____BaO + ____H2O

Type of reaction:

b. ____H2 (g) + ____O2 (g) ( ____H2O (l)

Type of reaction:

c. ____Na (s) + ____O2 (g) ( ____Na2O (s)

Type of reaction:

d. ____Al2O3 (s) ( ____Al (s) + ____O2 (g)

Type of reaction:

6. Describe what happens in a single replacement reaction.

7. Balance the following single replacement reaction and calculate the molecular weight of each compound to prove that the law of conservation of mass applies.

a. Chemical equation: ____Fe (s) + ____CuCl2 (aq) ( ____FeCl3 (aq) + ____Cu (s)

Molecular weight: _______g + _________g = __________g + _________g

Total weight: ________________g = ________________g

8. Describe what happens in a double replacement reaction.

9. Balance the following double replacement reaction and calculate the molecular weight of each compound to prove that the law of conservation of mass applies.

a. Chemical equation: ___Na2SO4 (aq) + ___CaCl2 (aq) ( ___CaSO4 (s) + ___NaCl (aq)

Molecular weight: __________g + ___________g = _________g + __________g

Total weight: _________________g = _________________g

10. Balance the following chemical equations and label each as either synthesis, decomposition, single replacement, or double replacement.

a. ___Ca (s) + ___H2O (l) ( ___Ca(OH)2 (aq) + ___H2 (g)

Type of reaction:

b. ___KOH (aq) + ___H2SO4 (aq) ( ___K2SO4 (aq) + ___H2O (l)

Type of reaction:

c. ___K (s) + ___Cl2 (g) ( ___KCl (s)

Type of reaction:

d. ___Cl2 (g) + ___NaBr (aq) ( ___NaCl (aq) + ___Br2 (l)

Type of reaction:

e. ___Na2O (s) + ___H2O (l) ( ___NaOH (aq)

Type of reaction:

f. ___NaClO3 (s) ( ___NaCl (s) + ___O2 (g)

Type of reaction:

g. ___Al(NO3)3 (aq)+ ___H2SO4 (aq) ( ___Al2(SO4)3 (aq)+ ___HNO3 (aq)

Type of reaction:

11. Describe what happens in a combustion reaction.

12. Balance the following combustion reactions and calculate the molecular weight of each compound to prove that the law of conservation of mass applies.

a. Chemical equation: ____CH4 (g) + ____O2 (g) ( ____CO2 (g) + ____H2O (g)

Total weight: ________________g = ________________g

Word Equations

For each of the following write:

A. Substitute symbols and formulas for names.

B. Write the state of matter for each compound or element in the reaction.

C. Balance the reaction.

D. Identify the type of reaction.

1. Solid aluminum metal reacts with aqueous zinc chloride to produce solid zinc metal and aqueous aluminum chloride.

2. Solid iron and solid sulfur produce iron (II) sulfide in a solid form.

3. When solid potassium nitrate is heated, it forms solid potassium nitrite and oxygen gas.

4. Aqueous lead (II) nitrate and aqueous sodium iodide react to produce solid lead (II) iodide and aqueous sodium nitrate.

5. Liquid methane reacts with oxygen gas to form gaseous carbon dioxide and gaseous water.

6. Solid elemental zinc reacts with solid aluminum oxide to form solid zinc oxide and solid elemental aluminum.

7. Aqueous lead (II) nitrate reacts with a solution of lithium fluoride to form a solution of lithium nitrate and solid lead (II) fluoride.

8. Solid sodium oxide breaks down to produce solid elemental sodium and oxygen gas.

Work the following mole problems. SHOW YOUR WORK FOR COMPLETE CREDIT!

1. 254.45 atoms of KCl = ________________________ moles of KCl

2. 0.567 moles of CO = _______________________ grams of CO

3. How many grams are there in 7.4 moles of Ammonium nitrate (NH4NO3)?

4. How many atoms are there in .45 moles of Magnesium chloride (MgCl2)?

5. How many grams are there in 7.5 x 1023 molecules of Magnesium chloride?

6. A group of students are conducting an experiment. There are two beakers, one empty and one with some solid sodium chloride (NaCl) in it. The empty beaker weighs 29.5g while the beaker with the sodium chloride has a mass of 250.5g. How many moles of sodium chloride are contained within the beaker?

Find the % composition of each of the elements within the following compounds:

1. sodium chloride

2. magnesium sulfate

3. aluminum hydroxide

4. diphosphorus trichloride

7. NutraSweet is 57.14% C, 6.16% H, 9.52% N, and 27.18% O.  Calculate the empirical formula of NutraSweet and find the molecular formula.  (The molar mass of NutraSweet is 294.30 g/mol)

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