a) Tetraphosphorus (P4), commonly known as white phosphorus, forms different compounds with chlorine (Cl2) depending on the amount of chlorine present. If chlorine is limited, phosphorus trichloride (PCl3) is formed. If there is an excess of chlorine, phosphorus pentachloride (PCl5) is formed.Write balanced equations for the two reactions of white phosphorous with chlorine.
b) Design an experiment that could be performed to verify each synthesis reaction. Include a hypothesis relating to whether PCl3 or PCl5 will be produced, information about the initial masses you would use, and possible problems that might arise.
c) Explain how your experiment will confirm the conservation of matter for each reaction.
d) Based on the ratio of moles of reactants in each case, predict the product of each trial of your experiment (PCl3 or PCl5) using your chosen initial masses. Explain your reasoning, and show any calculations.
e) Suppose you choose the initial masses so that both reactions produce PCl3. Explain how both of these chemical reactions obey the law of definite proportions, even though they produce different numbers of moles of the product. Justify your answer with calculations.
I know the answers to a and b
What is it?
a) Balanced equations for the two reactions are as follows:
For the reaction between white phosphorus and limited chlorine (PCl3 formation):
P4 + 6Cl2 -> 4PCl3
For the reaction between white phosphorus and excess chlorine (PCl5 formation):
P4 + 10Cl2 -> 4PCl5
b) To verify each synthesis reaction, you can design the following experiments:
Experiment 1 (PCl3 formation):
Hypothesis: If white phosphorus reacts with limited chlorine, then phosphorus trichloride (PCl3) will be produced.
Procedure: Take a known mass of white phosphorus and chlorine in a container. Carefully control the amount of chlorine to limit it. Allow the reaction to occur under controlled conditions.
Possible Problems: Ensuring the complete consumption of reactants, maintaining controlled conditions of temperature and pressure.
Experiment 2 (PCl5 formation):
Hypothesis: If white phosphorus reacts with an excess of chlorine, then phosphorus pentachloride (PCl5) will be produced.
Procedure: Take a known mass of white phosphorus and chlorine in a container. Introduce an excess of chlorine. Allow the reaction to occur under controlled conditions.
Possible Problems: Ensuring the complete consumption of reactants, maintaining controlled conditions of temperature and pressure.
c) The conservation of matter can be confirmed for each reaction through experimental observation. By measuring the masses of the reactants before the reaction and the masses of the products after the reaction, you can compare them to confirm that the total mass remains unchanged. Any minor discrepancies can be attributed to experimental errors.
d) Based on the ratio of moles of reactants, we can predict the product of each trial of the experiment using the chosen initial masses. Assuming the reaction goes to completion:
In the case of PCl3 formation:
Given the balanced equation: P4 + 6Cl2 -> 4PCl3
If you start with a known mass of white phosphorus (P4) and calculate the moles, you can use the stoichiometric ratio of P4 to PCl3 to determine the expected number of moles of PCl3 produced.
Example calculation:
Suppose the mass of white phosphorus (P4) is 5 grams.
Molar mass of P4: 123.88 g/mol
5 grams of P4 is equal to: 5 g / 123.88 g/mol = 0.04032 moles of P4
From the balanced equation, we see that 1 mole of P4 reacts to produce 4 moles of PCl3. Therefore, for 0.04032 moles of P4, we would expect: 0.04032 moles x 4 moles/mole = 0.16128 moles of PCl3.
e) If you choose the initial masses so that both reactions produce PCl3, the law of definite proportions is still obeyed. This law states that a chemical compound will always contain the same elements in the same fixed proportions by mass.
To justify this, let's consider two scenarios where PCl3 is the product:
Scenario 1:
Starting with 5 grams of white phosphorus (P4), we calculate the moles and determine the expected moles of PCl3 (as shown in part d).
Scenario 2:
Starting with 10 grams of white phosphorus (P4), we calculate the moles and determine the expected moles of PCl3.
Even though the initial mass of white phosphorus is different in each scenario, both reactions produce the same number of moles of PCl3 (0.16128 moles in the example). Therefore, the mass ratio of P to Cl in the product (PCl3) remains the same, demonstrating the law of definite proportions.