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junior college 1 | H2 Maths
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Good evening! Can someone please help me with this question? I have trouble finding the mass of NaCl, i could only find the moles of Hcl & NaOH and i’m stuck afterwards. Thank you so much
Date Posted: 4 years ago
Views: 260
Good evening Sonia! I will have a look later if I have the time.
Since 22.4 cm3 of 0.5 mol/dm3 HCl is used,
Number of moles of HCl used
= 0.0224 x 0.5
= 0.0112 mol
Since NaOH reacts with HCl in a 1 : 1 ratio, number of moles of NaOH reacted
= 0.0112 mol
This means that the residual quantity of NaOH before reaction with HCl must have been 0.0112 x 10 = 0.112 mol in the 250 cm3 solution, since there is 0.0112 mol in every 25 cm3.
Initially 100 cm3 of 2.00 mol/dm3 is used.
Number of moles of NaOH at first
= 0.1 x 2.00
= 0.2 mol
This means that 0.2 - 0.112 = 0.088 mol of NaOH must have been reacted with the ammonium chloride.
Equivalent mass of NH4Cl
= 0.088 * (14 + 4 * 1 + 35.5)
= 4.708 g
and as such, mass NaCl in the contaminated 5 g sample
= 5 g - 4.708 g
= 0.292 g
Number of moles of HCl used
= 0.0224 x 0.5
= 0.0112 mol
Since NaOH reacts with HCl in a 1 : 1 ratio, number of moles of NaOH reacted
= 0.0112 mol
This means that the residual quantity of NaOH before reaction with HCl must have been 0.0112 x 10 = 0.112 mol in the 250 cm3 solution, since there is 0.0112 mol in every 25 cm3.
Initially 100 cm3 of 2.00 mol/dm3 is used.
Number of moles of NaOH at first
= 0.1 x 2.00
= 0.2 mol
This means that 0.2 - 0.112 = 0.088 mol of NaOH must have been reacted with the ammonium chloride.
Equivalent mass of NH4Cl
= 0.088 * (14 + 4 * 1 + 35.5)
= 4.708 g
and as such, mass NaCl in the contaminated 5 g sample
= 5 g - 4.708 g
= 0.292 g
Sonia, I will write out a full explanation of my thoughts on this problem later by 2 am after I return home.
See 2 Answers
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Good evening Sonia! Here are my thought processes for this question. I will send in my remaining workings soon. Let me know if you need more explanation for my workings.
Date Posted:
4 years ago
done
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Good evening Sonia! This second page completes my working for this question. Let me know if my explanations and thought processes are not clear and I will do my best to explain them again.
Date Posted:
4 years ago
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