Chemistry Quarter 4 MCA Review
Critical Thinking and Mastery Problems:
1. Write a balanced equation for each of the following reactions.
a. Strontium reacts with water to form strontium hydroxide and hydrogen gas
b. Iron and oxygen are prepared by heating iron (II) oxide.
c. Aluminum sulfide and water form aluminum hydroxide and hydrogen sulfide.
d. Tetra phosphorous decaoxide and water form phosphoric acid
2. Calculate the molecular formulas for the following compounds.
a. C2H4O and the gmm is 88g/mol
b. CH and the gmm is 104 g/mol
c. Percent composition is 26.7%C, 71.1%O, and 2.2% H.
3. Graph the heating curve of water, identify the dependent and independent variables, the regions of the graph where temperature is constant, indicate where phases exist, identify where the heat of fusion, vaporization, and specific heats would apply.
4. Calculate the number of kilojoules needed to change 17.0g of ice at -15.00 oC to steam at 100 oC
5. Calculate the enthalpy change, DH in kJ, for the following reaction
2NO + O2 ------2NO2
DH = 90.25 kJ for NO
DH = 33.18 kJ for NO2 Remember ( product – reactant )
6. When 70g of N2 are reacted with excess H2, 77.0g of NH3are formed. Calculate the percent yield. N2 + 3H2 ------2NH3
7. For the reaction 2Al + 3Cl2 ------2AlCl3 if 100g of Al reacts with 223g of Cl2 calculate the mass of AlCl3 formed. Remember to find the limiting reactant first!
8. Answer the following problems using the following equation.
4NH3 + 6NO ------5N2 + 6H2O
a. How many moles of H2O are formed by the reaction of 4.50 moles of NH3 with an excess of NO?
b. What mass of N2 is formed by the reaction of 12.0g of NO with excess NH3?
c. Calculate the volume of N2 formed by the reaction of 7.50L of NH3 with excess NO.
d. Using the heats of formation given, calculate DH of this reaction. Remember it is the sum of the products – reactants. H2O = -241.8kJ/mol NH3 = -46.2kJ/mol, and NO = 90.4kJ/mol
e. Calculate DH if 12.0g of NO react with an excess NH3
Multiple Choice:
1. What is the molecular mass of nitrogen gas ______
2. The boiling point on the Kelvin scale is ______
3. A unit of heat in the SI system is ______
4. The gram atomic mass of Nitrogen is ______
5. The unit of volume in the SI system is ______
6. How much heavier is benzene than water?
7. The mass of one mole of Sulfuric acid is ______
8. The mass of three moles of carbon dioxide is ______
9. The number of molecules in 4 moles of sodium phosphate is ______
10. The mass of 45 liters of chlorine gas at STP is ______
11. The amount of moles in 4.00g of sodium is ______
12. The mass of one molecule of carbon monoxide is ______
13. The number of moles in 35.7 liters of oxygen gas at STP is ______
14. The number of molecules in 7.89 liters of carbon dioxide at STP is ______
15. Which is the lighter particle water or carbon monoxide?
16. The mass percentage of oxygen in sulfur trioxide is ______
17. Give the mass of copper contained in a 35g sample of copper (II) oxide is ______.
18. The mass percentage composition of acetic acid is 40.0% C, 6.73% H, and 53.0% 0. What is its simplest formula?
19. Give the formula of a compound composed of 22.6% N and 77.4 % O.
20. Give the simplest formula for a substance composed of 27% C and 73% O.
21. List some possible molecular formulas for the empirical formula CH2Cl2
22. Find the molecular formula if the mass is 28.0 amu and the compound contains 14.3% H and 85.7% C.
23. Use the following equation: 2C + 02 ----- 2CO
a. The number of moles of CO formed by the reaction of 7 moles of oxygen in an excess of carbon
b. The number of moles formed by the reaction of 4.30g of carbon with an excess of oxygen
c. The number of grams of CO formed by the reaction of 14g of oxygen with an excess of carbon
d. The volume of oxygen needed to produce 5.34 liters of CO at STP
24. Balance and use the following equation: K + 02 ------K20
a. The moles of potassium oxide formed by the reaction of 5 moles of K with an excess of oxygen gas.
b. The mass of potassium oxide formed by the reaction of 0.233 moles of potassium with an excess of oxygen
c. The mass of potassium oxide formed by the reaction of 4.65g of potassium with an excess of oxygen.
d. The volume of oxygen at STP needed to react with 7.22g of potassium
25. Write the balanced equation of the decomposition of potassium chlorate.
a. if 40g of potassium chlorate produces 10L of oxygen, what is the percent yield?
26. A chemical reaction that produces heat is called ______
27. As the temperature of a fixed volume of a gas increases, the pressure will ______
28. As the temperature of a gas increases at a constant pressure, the volume of a gas ______
29. The law which predicts how the volume of a gas changes as the pressure changes at a constant temperature is known as ______
30. The standard temperature at STP is ______
31. Substances that speed up chemical reactions but are not permanently changed are ______
32. If 7g of nitrogen gas is contained in a 5L flask at 880mmHg, what is the temperature of the gas?
33. An unknown gas is found to diffuse 2 times faster than SO3 gas under the same conditions, what is the molecular mass of the unknown gas?
34. Balance the following equation and answer the following questions.
H + N ------NH3 DH = -92.4kJ
a. Calculate DH if 0.488g of hydrogen gas react with an excess of nitrogen
b. Calculate the grams of nitrogen gas needed to produce 233kJ in an excess of Hydrogen.
c. Calculate DH if 12g of nitrogen gas react with an excess of hydrogen
35. What is the molecular mass of a gas which has a density 2.72 times that of nitrogen gas?
36. What is the density of C2H6 at STP?
37. Correct to STP: 6.00L at 42oC and 746mmHg
38. What pressure is needed to change the volume of 300L of oxygen at 3.52atm to 350L at the same temperature?