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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. Would you mind writing your comment up and posting it as an answer? Asking for help, clarification, or responding to other answers. The molarity of NaF (sodium fluoride) in a brand of toothpaste was found to be 3.16*10 -4 M. How do I determine the %w/v (percent weight by volume) of fluoride ion in the toothpaste from the molarity? A linear regression line was obtained; $$\log(\ce{[NaF]})~(\mathrm{mol~L^{-1}})~ \mathrm{vs~EMF}: How to solve a linear problem A x = b in PETSC when matrix A has zero diagonal enteries? @JasonPatterson I think you already pretty much gave the answer. 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. Considers the theory behind the operation of the ion-selective electrode and its application to determine the fluoride in toothpaste. h�bbd``b`Z $�� �rH0��$*A�pn.�x ⶁX� B��H�e`$��ϸ�@� n� Working with your numbers gives me the same result through moles of $\ce{NaF}$. Examples of back of envelope calculations leading to good intuition? Since we know the original mass of this sample, we can calculate the concentration in ppm based on that value. 49 0 obj <>/Filter/FlateDecode/ID[<1F6A54D718C2F8DE468B1D676AB45DF7><81D22B0591931F4CB526DBD73E3CFDA0>]/Index[34 28]/Info 33 0 R/Length 76/Prev 143969/Root 35 0 R/Size 62/Type/XRef/W[1 2 1]>>stream Has the European Union taken any concrete steps towards reducing its economic dependency on China? Analysis of Fluoride in Toothpaste The toothpaste sample should be prepared and analyzed at the same time the standards and your prepared unknown. To learn more, see our tips on writing great answers. I then multiplied by the factor: $\frac{198}{0.750}$ to obtain $0.074454015~\mathrm{g}$ of $\ce{F-}$ in the $198~\mathrm{g}$ of toothpaste. Thanks for contributing an answer to Chemistry Stack Exchange! [��&��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�� It will be the same concentration as in the larger sample. How can I label staffs with the parts' purpose, Two PhD programs simultaneously in different countries. 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 what is the ppm of $\ce{F-}$ in $198~\mathrm{g}$ of toothpaste? Determine the ppm F-in your unknown and in the toothpaste from the calibration curve. &�R ��]@,����gd0 ��� Regular OTC fluoride toothpastes are effective cavity preventers too. 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. It's similar in concept to percent mass, but instead of … y = 59.8x +600.8$$ endstream endobj 38 0 obj <>stream @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? 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 analyte concentration (μg/mL) in the original unknown solution (Cunk) can then be determined by dividing by the volume of the unknown fluoride solution (Vunk). endstream endobj startxref hޤVmo�8�+��b��b�/�P m�.����: �7�R�����#%+qr����E��DJ�CEq�. 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�. i get the same answer. 4Ҹ��߂�����˺%|ݒ��῝A ��n?�[æ��^���������/w^9J��Z��j'x�? ���(܃`ٰ�f��?r�f��>D���[�a�ԕ�$�&�~�����p�FکRDl\�����}}]��*J`�s�\�Վ�MQ�.f�F�����z�W�V��o4�T��iv?���4�,_�C�l��=�hBfb�X�u������WH��Ȕ�m�������M�:o5ټ��m��WE�fOE5��b�Mkn^�y� a�N毼�qĲφb�5?� jN�2/�\*A@GMO�I4�FU���V�4��߽�K���98�! Construct a polyhedron from the coordinates of its vertices and calculate the area of each face. My strands of LED Christmas lights are not polarized, and I don't understand how that works. How come it's actually Black with the advantage here? I get the following: 61 0 obj <>stream =�-�n ��|�R�,/3T�̢%�%i#G]��q&J6��%�1��d8�.2k�%dV��F�� kҋ5�͚! It only takes a minute to sign up. First you need to take the equation for molarity: �'b:ژ1s�q���+���>4�C�O��[U� How many pawns make up for a missing queen in the endgame? %%EOF ���G���RN�TCP��=3��\i��m`lp�s�j��T�l~Zk�ny!2�F��ms�5E ��_��}�� Find the coordinates of a hand drawn curve. endstream endobj 39 0 obj <>stream Chemistry Stack Exchange is a question and answer site for scientists, academics, teachers, and students in the field of chemistry. 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? By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy. � �9� If a person is dressed up as non-human, and is killed by someone who sincerely believes the victim was not human, who is responsible? I multiplied by $18.998~\mathrm{g~mol^{-1}}$ to obtain $0.000283527~\mathrm{mol}$ of $\ce{F-}$. Accurately weigh about 0.2 g of toothpaste into a 100 mL beaker. Making statements based on opinion; back them up with references or personal experience. Use MathJax to format equations. h�b```f``2d`a`��� �� @ �X�$��'���\�L��g�^`�`��``h�� ��109�Ҽ@�6����9�ё*��_\�>(t>��a��u� To subscribe to this RSS feed, copy and paste this URL into your RSS reader. I follow your method through moles of fluoride, but at that point, your units get messed up. ���� *�H��>M�����MN5�������6�n�s}l;�v���UO*EV��&��o��>���ծ Express the fluoride ion concentration in the toothpaste as %F. MathJax reference. I'm stuck here, how can I calculate the ppm? By using our site, you acknowledge that you have read and understand our Cookie Policy, Privacy Policy, and our Terms of Service. $0.7540~\mathrm{g}$ of toothpaste was diluted in a$50~\mathrm{mL}$ and tested to obtain a EMF value of $390$. KEYWORDS (Audience): Second-Year Undergraduate; KEYWORDS (Domain): Analytical Chemistry ; KEYWORDS (Pedagogy): Hands-On Learning / Manipulatives; KEYWORDS (Subject): Fluorine; Cited By This article is cited by 21 publications. 1. 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. $\frac{0.0002835 \textrm{ g } \ce{F-}}{0.7540 \textrm{ g toothpaste}}\times 1000000 = 376.0\textrm{ ppm }\ce{F-}$. It's similar in concept to percent mass, but instead of parts per hundred, it uses parts per million. The expected value of fluoride in toothpaste is $1000~\mathrm{ppm}$. Parts per million is a mass-based concentration measure. Stack Exchange network consists of 176 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

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