However, at this point you can multiply by the molar mass of fluoride, 18.998 g/mol, to get grams of fluoride, not moles, specifically, 0.0002835 g $\ce{NaF}$. =�-�n
��|�R�,/3T�̢%�%i#G]��q&J6��%�1��d8�.2k�%dV��F�� kҋ5�͚! Parts per million is a mass-based concentration measure. I plugged in $390$ into the eqn to get $-3.525$, taking the antilog to obtain $0.0002985$, and times it by the volume $0.05~\mathrm{L}$ to get the moles of $\ce{NaF}$. It only takes a minute to sign up. A toothpaste sample is prepared as follows: weigh the beaker plus the sample of toothpaste to determine the net weight of the toothpaste sample. h�b```f``2d`a`��� �� @ �X�$��'���\�L��g�^`�`��``h�� ��109�Ҽ@�6����9�ё*��_\�>(t>��a��u� Accurately weigh about 0.2 g of toothpaste into a 100 mL beaker. �'b:ژ1s�q���+���>4�C�O��[U� 1. How many pawns make up for a missing queen in the endgame? First you need to take the equation for molarity: what is the ppm of $\ce{F-}$ in $198~\mathrm{g}$ of toothpaste? rev 2020.11.24.38066, The best answers are voted up and rise to the top, Chemistry Stack Exchange works best with JavaScript enabled, Start here for a quick overview of the site, Detailed answers to any questions you might have, Discuss the workings and policies of this site, Learn more about Stack Overflow the company, Learn more about hiring developers or posting ads with us, I'm having difficulty getting your expected answer. How come it's actually Black with the advantage here? @Spencer-Trinh I'd guess you're past caring at this point, but I'm curious, was this a word problem or a lab experiment? }c)!�b�ZY ��N����I�Z�^gC^$��kR;/�c����I��[��H��:)~#7�G?oO'����y���Λ�şrDsDF�qdp]���$J��� �3���ϣKxB)�M�?��8}N���:�A� n�P�-o�ca�V� ]�' �;tџd����=M�G@��R�f2« �����G�L;P�0�q\"��DG��v��t8���kh���p8~p�g�n��!x��k�{R}���kV�A�]LV�lav��Q���4���~֗�������7�0��&��|˼=9&��6�i{��+Pв�չ�*L����^*��s*B�y�������Z��n�����6���8��M��� H��SMs�0��W�Q:XH��6ЖN��qJrP� u�MmA��]�4�;�x�+���V�/K�>�d��1�M���$>cT�[ $\frac{0.0002835 \textrm{ g } \ce{F-}}{0.7540 \textrm{ g toothpaste}}\times 1000000 = 376.0\textrm{ ppm }\ce{F-}$. 34 0 obj
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@JasonPatterson I think you already pretty much gave the answer. MAINTENANCE WARNING: Possible downtime early morning Dec 2/4/9 UTC (8:30PM…, “Question closed” notifications experiment results and graduation, Calculating Redox Potential; Coupled Reactions, Calculating the pH of a saturated calcium fluoride solution. NMR detects the soluble fluoride content in toothpastes, which is the most important parameter in … %PDF-1.5
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The MQCbenchtop Nuclear Magnetic Resonance (NMR) analyser offers a simple, non-destructive and rapid method for the measurement of fluoride concentration in toothpastes. A linear regression line was obtained; $$\log(\ce{[NaF]})~(\mathrm{mol~L^{-1}})~ \mathrm{vs~EMF}: The ppm unknown can be determined using the following equation: Ppm F- unk= ppm F -from graph x (100 mL/5mL) = ppm F-(graph) x 20. It's similar in concept to percent mass, but instead of … Find the coordinates of a hand drawn curve. Examples of back of envelope calculations leading to good intuition? endstream
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By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy. y = 59.8x +600.8$$ Use MathJax to format equations. Multiplying by the molar mass gives you 0.0002835. thanks for your support, i guess it has to deal with the regression line, it must be wrong? I multiplied by $18.998~\mathrm{g~mol^{-1}}$ to obtain $0.000283527~\mathrm{mol}$ of $\ce{F-}$. H�lSM��0��W�іB ��V�^�[���+ǎl�i�}�Ƥ�v/0��]U�Z�]U#���V���z����.��4���ڠ���p�3߉5;p�a^Z�ۤ��[�+�cw8 �ۿ����N� �xT�i���HP��4F��Ο��*���g}R�. MathJax reference. 61 0 obj
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Working with your numbers gives me the same result through moles of $\ce{NaF}$. $0.7540~\mathrm{g}$ of toothpaste was diluted in a$50~\mathrm{mL}$ and tested to obtain a EMF value of $390$. A review of dental literature performed by Walsh concluded that a dentifrice must deliver a fluoride concentration of at least 1000 ppm to produce significant anticavity effects. The molecular weight of NaF is 41.99, and the density of the toothpaste is 0.9681g/cm 3. However, at this point you can multiply by the molar mass of fluoride, 18.998 g/mol, to get grams of fluoride, not moles, specifically, 0.0002835 g N a F. Parts per million is a mass-based concentration measure. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Thanks for contributing an answer to Chemistry Stack Exchange! ����
I follow your method through moles of fluoride, but at that point, your units get messed up. Analysis of Fluoride in Toothpaste The toothpaste sample should be prepared and analyzed at the same time the standards and your prepared unknown. Due to stoichiometry, this also equals $1~\mathrm{mol}$ of $\ce{F-}$. Boil the solution gently for 2-3 minutes. To learn more, see our tips on writing great answers. [��&��E!���P)t.�|�?�s%��`�C� �Ǘ��_4Q�&��ٮ���� �6`η{>�9��d�;�����[~h�PWQ�Ӓf��Qq?jd[���pl��v��ytP�n���I�v������3��XF}�"Z�8�t?sr0���q��,Oz塡$t���X�y���p�u�L���(�A�)#��]�i�M�v( ��/1�� Since we know the original mass of this sample, we can calculate the concentration in ppm based on that value. Asking for help, clarification, or responding to other answers. Sodium fluoride has a molecular weight of 42 MW Na (23) + F (19) = 42 NaF in toothpaste is 0.243% weight/volume of NaF (read the toothpaste tube) Convert % NaF to mg/g of NaF compound multiply by 10 = 0.243 x 10 = 2.43 mg NaF/g My strands of LED Christmas lights are not polarized, and I don't understand how that works. The expected value of fluoride in toothpaste is $1000~\mathrm{ppm}$. Would you mind writing your comment up and posting it as an answer? Determine the ppm F-in your unknown and in the toothpaste from the calibration curve. endstream
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