A piece of glassware labelled A in the diagram below was filled with a standard solution of hydrochloric acid (HCl) that had a concentration of 0.13 M - Leaving Cert Chemistry - Question 2 - 2014
Question 2
A piece of glassware labelled A in the diagram below was filled with a standard solution of hydrochloric acid (HCl) that had a concentration of 0.13 M. This solution... show full transcript
Worked Solution & Example Answer:A piece of glassware labelled A in the diagram below was filled with a standard solution of hydrochloric acid (HCl) that had a concentration of 0.13 M - Leaving Cert Chemistry - Question 2 - 2014
Step 1
Explain the underlined term.
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Answer
The underlined term 'solutions of known concentration' refers to solutions that have a precise, measured concentration of a solute, allowing accurate calculations and comparisons during chemical reactions, particularly in titrations.
Step 2
Name the pieces of equipment A, B and C.
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Name another piece of glassware required to carry out the titration experiment.
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Answer
A conical flask (also known as a beaker, depending on the experiment requirements) is used to contain the solution being tested during the titration process.
Step 4
What use is made in the experiment of the piece of glassware you have named?
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The conical flask is used to mix the reactants and allow for the titration process to occur, providing a stable environment for the reactions and making it easier to swirl and mix without spilling.
Step 5
Describe the procedure for rinsing B before using it to measure the sodium hydroxide solution.
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To rinse the pipette (B), first fill it with deionised (distilled) water and allow it to drain out completely. Then, rinse it with the sodium hydroxide solution by drawing a small amount into the pipette and then expelling it back into the source container. This ensures that any residual water is removed, and the pipette is conditioned for accurate measurement.
Step 6
State one use of C during the titration.
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C, the wash bottle, is used to rinse down the sides of the titration flask with deionised (distilled) water to ensure all reagents are brought together and mixed effectively during the titration.
Step 7
Name a suitable indicator for this titration.
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Answer
Methyl orange is a suitable indicator for this titration.
Step 8
State the colour change of the indicator at the end point.
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The colour changes from yellow (in alkaline solution) to red (in acidic solution) at the end point of the titration.
Step 9
Find the concentration of the sodium hydroxide solution (i) in moles per litre.
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Answer
To calculate the moles of HCl used:
Moles of HCl = Concentration × Volume = 0.13 M × 0.0174 L = 0.002262 mol
Since the reaction ratio is 1:1, moles of NaOH = 0.002262 mol.
Now, to find concentration of NaOH:
Concentration of NaOH = Moles / Volume = 0.002262 mol / 0.025 L = 0.09048 M.
Step 10
Find the concentration of the sodium hydroxide solution (ii) in grams per litre.
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To find the grams per litre of NaOH:
First, calculate the molar mass of NaOH = 23 (Na) + 16 (O) + 1 (H) = 40 g/mol.
Now, using the concentration:
Grams per litre = Concentration × Molar Mass = 0.09048 mol/L × 40 g/mol = 3.6192 g/L.
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