Calculating Moles & Molarity of KHP & NaOH

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Discussion Overview

The discussion revolves around the calculation of moles and molarity in a titration experiment involving potassium hydrogen phthalate (KHP) and sodium hydroxide (NaOH). Participants explore the significance of molar mass and the correct approach to calculating moles and molarity based on experimental data.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant describes their experimental procedure and calculations for determining moles of KHP and molarity of NaOH, initially using incorrect molar mass values.
  • Another participant questions the assumption that KHP contains phosphorus, suggesting that it may be an acid salt.
  • Some participants clarify that the correct molar mass of KHP is 204.22 g/mol, and that the mole ratio between NaOH and KHP is 1:1.
  • There is a discussion about whether the volume of distilled water added should be considered when calculating the molarity of NaOH.
  • One participant expresses uncertainty about the implications of the molar mass and the identity of KHP.
  • Another participant points out that KHP can refer to different compounds, which may lead to confusion in calculations.

Areas of Agreement / Disagreement

Participants generally agree on the need to use the correct molar mass for KHP and the 1:1 mole ratio with NaOH. However, there is disagreement regarding the identity of KHP and its implications for the calculations, leading to unresolved questions about the significance of the molar mass and the correct approach to determining molarity.

Contextual Notes

There are limitations in the assumptions made about the composition of KHP and its molar mass, as well as the potential impact of the volume of distilled water on molarity calculations. These aspects remain unresolved within the discussion.

Prone17
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what i did:

1) i put 0.737 g of KHP in a flask
2) then added ~25 mL of distilled water
3) and then titrated 34.06 mL of NaOH into it to get its equilibrium point,

how would i find: 1. the moles of KHP, and 2. the molarity of NaOH? and would the molar mass have any significance?

1. the moles of KHP
i thought i would turn .737 g into moles by dividing by the masses given in the periodic table (K=39.1g, H=1.01g, P=30.9g) = 71.08g in total

which gives 0.0104 moles of KHP

2. the molarity of NaOH

since I am pretty sure the mole ratio of NaOH and KHP is 1:1, i used 0.0104 moles of NaOH

M=moles/L
M= 0.0104/.03406
M= .305 M

is all this correct? and if so, why did they ask me for the molar mass of KHP (which i googled to be 204.22 g/mol) ? how is this even significant?

also, when doing the molarity part, would i have to take into consideration the 25mL of distilled water i added at the beginning of the experiment, or just the amount of NaOH i added?
 
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Prone17 said:
what i did:

1) i put 0.737 g of KHP in a flask
2) then added ~25 mL of distilled water
3) and then titrated 34.06 mL of NaOH into it to get its equilibrium point,

how would i find: 1. the moles of KHP, and 2. the molarity of NaOH? and would the molar mass have any significance?

1. the moles of KHP
i thought i would turn .737 g into moles by dividing by the masses given in the periodic table (K=39.1g, H=1.01g, P=30.9g) = 71.08g in total

which gives 0.0104 moles of KHP

2. the molarity of NaOH

since I am pretty sure the mole ratio of NaOH and KHP is 1:1, i used 0.0104 moles of NaOH

M=moles/L
M= 0.0104/.03406
M= .305 M

is all this correct? and if so, why did they ask me for the molar mass of KHP (which i googled to be 204.22 g/mol) ? how is this even significant?

also, when doing the molarity part, would i have to take into consideration the 25mL of distilled water i added at the beginning of the experiment, or just the amount of NaOH i added?

I don't think the KHP you're using here has any phosphorus in it, rather it's an acid salt as you later discover
 
sjb-2812 said:
I don't think the KHP you're using here has any phosphorus in it, rather it's an acid salt as you later discover

i'm not sure what that means. I'm just going by my lab book. i just know that the experiment was to titrate NaOH into KHP, and as far as i know, this was not a trick question. the bottle i took the KHP from said "KHP" on it.
 
When you calculated the number of moles of KHP in
1. the moles of KHP
i thought i would turn .737 g into moles by dividing by the masses given in the periodic table (K=39.1g, H=1.01g, P=30.9g) = 71.08g in total

you made an assumption that the compound in question was literally KHP (one atom of potassium, one of hydrogen, and one of phosphorus). However, the molecular mass you got from google is not consistent with this. KHP can mean different things, and it's not totally your fault. It seems to me you are doing something similar to http://www.google.co.uk/search?q=ktp+standardization+naoh
 
sjb-2812 said:
When you calculated the number of moles of KHP in


you made an assumption that the compound in question was literally KHP (one atom of potassium, one of hydrogen, and one of phosphorus). However, the molecular mass you got from google is not consistent with this. KHP can mean different things, and it's not totally your fault. It seems to me you are doing something similar to http://www.google.co.uk/search?q=ktp+standardization+naoh

yes i did assume that. but then i realized that to find the moles of KHP (part 1 of my question), i would divide the mass of KHP (0.737 g) by the molar mass of KHP (204.22 g/mol). is this correct? and yes, that link is exactly what i did in the experiment.
 
Just a guess: Are you abbreviating Potassium Biphthalate with "KHP"?
 

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