Semester BCR's Flashcards
- list lab equipment
- explain how each item is used in the procedure
- list any safety equipment needed and how it is used in the procedure
- describe how this procedure might be used in a situation outside the chemistry classroom
Filter funnel + paper
Test tube OR conical flask OR beaker
Place the suspension in a filter funnel lined with filter paper, and collect the filtrate with a beaker/conical flask/test tube if the aqueous solution is required for further use or dispose of the filtrate over a sink and then rinse the sink. Give the residue time to dry by leaving the filter paper in the sun for a few minutes making sure there would be no wind to blow the residue.
There would not really be any safety equipment used in this procedure outside the usual goggles, lab coat and rubber gloves.
You could use this technique on a small scale to purify drinking water known to be contaminated with toxic barium ions or on a larger scale to purify a small lake with the same problem (but in that case there would be no need/possibility of filtering)
Two solids, A and B, are located in the same family on the periodic table. A sample of each is placed in a beaker of HCL. Substance A produces few bubbles, while substance B bubbles vigorously.
- what the bubbles indicate
- where the substances are located in relation to one another on the periodic table and the activity series
- the name of a family the substances could belong to
- which substance will have a larger atomic radius
- which substance will have a larger first ionization energy
The alkali metals (Na, K, Rb…) react violently with water, producing enough heat to ignite the hydrogen that is produced.
The alkaline earth metals, on the other hand, react with water to produce hydrogen gas, which bubbles to the surface, but do so much less violently. Clean Ca, Sr, and Ba will react vigorously with water to produce H2 gas, while clean Mg will barely react.
A can be Mg
B can be Ca
Ca is below Mg on the PT, and Ca is above Mg in the activity series, indicating that Ca will reduce Mg2+, but Mg will not reduce Ca2+.
Clearly, Ca is larger than Mg since Ca has an additional energy level. Mg has the greater first ionization energy since the outter electrons are closer to the nucleus.
Students’ observations of three chemical reactions are shown in the table below. Use their data and the solubility table to classify each of the types of reactions.
Be sure to include
• the name of each type of reaction
• evidence that supports how each type is classified
• the reactants and products for each reaction
Reaction Initial Observations / Notes Final Observations / Notes
1. Clear, colorless KI solution is added to clear, colorless Pb(NO3)2 solution in a beaker. A yellow solid appears in a clear liquid.
The yellow solid is lead (II) iodide.
2. Magnesium (Mg), a solid silver-colored ribbon, is ignited in the flame of a Bunsen burner.
The Mg burns with a bright white light. White ashes remain after the Mg burns.
Magnesium oxide is produced.
3. Mercury (II) oxide, a red, powdery solid, is heated in a test tube. Mercury metal condenses on the walls of the test tube. A glowing splint inserted into the mouth of the test tube burns brightly.
- This is a double replacement reaction. It is double replacement because the two compounds sort of “swap” ions, check the balanced equation:
2KI + Pb(NO3)2 –> 2KNO3 + PbI2 - This is a synthesis reaction because In a synthesis reaction two or more chemical species combine to form a more complex product
2Mg + O2 –> 2MgO - This is a decomposition reaction, it is so because upon heating the compound decomposes into the elements that it is made of. The splint glows because of the excess oxygen released from the HgO.
2HgO –> 2Hg + O2
Propane is used as a fuel in most gas grills to cook food on during the warm summer months. When the propane is burned, the following reaction takes place:
C3H8(l) + 5O2(g) (arrow) 3CO2(g) + 4H2O(g)
A standard propane tank contains 6804 g of propane. Determine how many molecules of carbon dioxide gas are released into the atmosphere when an entire tank of propane is burned.
In your answer be sure to:
• Describe the type of chemical reaction the propane undergoes
• Calculate the number of moles of propane used in the reaction
• Explain the mole ratio between propane and carbon dioxide in this reaction
• Calculate the number of moles of carbon dioxide produced
• Calculate the number of molecules of carbon dioxide produced
It is a combustion of a hydrocarbon.
The equation is balanced, so 1 mol C3H8 reacts with 5 mol oxygen to produce 3 mol CO2 and 4 mol H2O
Molar mass C3H8 = 12.01 x 3 + 1.01 x 8 = 44.11 g C3H8 / mol C3H8
Number of mol C3H8 in tank = 6804 g C3H8 / [44.11 g C3H8 / mol C3H8]
= 154.25 mol C3H8
Now 1 mol C3H8 produces 3 mol CO2
so 154.25 mol C3H8 produces 462.75 mol CO2
Number of molecules of CO2 produced when the whole tank burns = [462.75 mol CO2] x [6.022 x 10^23 molecules CO2 / mol CO2]
= 2.79 x 10^26 molecules CO2
A student burns a small amount of six solutions in the flame of a Bunsen burner and records the color for each. Her data are shown in the table below.
Solution Color Lithium chloride Red Sodium chloride Yellow Potassium chloride Violet Calcium chloride Red-orange Strontium chloride Red-orange Barium chloride Green
Analyze the results of the flame test colors. Be sure to include
• An explanation of the flame test results in terms of energy and electron movement
• An explanation of how the flame test can be used to identify ions
• The limitations of the flame test in identifying ions
When solutions of metals are heated in a flame, some of their electrons gain energy. These electrons move to higher energy levels, also known as their excited state. As the electron(s) return to their previous state, also known as the ground state, they give off energy in the form of light. The flame test can be used to identify ions because many metal ions produce characteristic colors once exposed to a flame. Limitations of using the flame test when identifying ions are the colors can typically be up to interpretations, and more than one metal may show the same color.
bobs chemistry teacher gives him a solid compound to use in a chemical reaction. the teacher tells him the compound is either sodium carbonate or sodium bicarbonate. Bob must determine the identity of the compound. He reacts the compound with excess HCl and measures the mass of the product. his data are shown here.
Mass of beaker: 50.52g
Mass of beaker and solid compound: 52.43g
Mass of beaker and dried product (NaCl): 52.63g
the balanced chemical equations are show below
- Na2CO3 + 2HCL —> H20 +CO2 +2NaCl
- NaHCO3 +HCl ——> H20 +CO2 + NaCL
Check what the two balanced equations are telling you:
1) 1mol Na2CO3 will produce 2 mol NaCl
2) 1 mol NaHCO3 will produce 1 mol NaCl
Check mol of NaCl produced:
Mass NaCl produced = 52.63-50.52 = 2.11g NaCl
Molar mass aCl = 58.44g/mol
2.11g NaCl = 2.11/58.44 = 0.036 mol NaCl
Mass of starting material = 52.43-50.52 = 1.91g
Molar mass Na2CO3 = 106g/mol
1.91g = 1.91/106 = 0.018 mol
From the equation , this will produce 0.018*2 = 0.036 mol NaCl
Which is what you have
Therefore the unknown compound is Na2CO3
I know it's not NaHCO3 because: Molar mass NaHCO3 = 84g/mol 1.91g = 1.91/84 = 0.023 mol NaHCO3 From the equation this will produce 0.0233 mol NaCl Which is not what you got. Therefore the compound is not NaHCO3
