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Numerade Educator



Problem 127 Medium Difficulty

Citric acid (right) is concentrated in citrus fruits and plays a central metabolic role in nearly every animal and plant cell. (a) What are the molar mass and formula of citric acid? (b) How many moles of citric acid are in 1.50 qt of lemon juice $(d=1.09 \mathrm{g} / \mathrm{mL})$ that is 6.82$\%$ citric acid by mass?


$\mathrm{C}_{6} \mathrm{H}_{8} \mathrm{O}_{7}$
$\operatorname{Mr}\left(\mathrm{C}_{6} \mathrm{H}_{8} \mathrm{O}_{7}\right)=192,12 \mathrm{g} / \mathrm{mol}$
$\mathrm{n}($ citric acid $)=0,55 \mathrm{mol}$


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Video Transcript

the image given is what's called the structural formula, and it tells us the atoms present on a molecule as well as how they're connected. So to write the molecular formula, we simply add up the different elements. You can see that there's carbon, and if you count them, there are six the blue or the hydrogen. 12345678 And finally the oxygen's. The reds are seven, so the molecular formula is C six, h, 807 and the molar masses simply adding up the individual more masses and multiplying by how Muneer present so six times the moulder massive carbon I just found on the periodic table, plus eight times the molar mass of hydrogen also on the periodic table, and seven times 15.999 which is more math of oxygen. This equals 192 0.12 grams per mole. So that's the molar mass, and we can use this information to make a conversion about different types of solutions. If we have, for example, 1.5 quarts of a solution, that's 6.8% citric acid, 6.82%. We can determine how many moles of the actual citric acid or present. We also know the density of the solution is 1.9 grams per mil. We'll start with their given quantity and we'll convert to milliliters using the conversion. We can then find grams using the density which we can then find grams of the citric acid and using the percentage. And finally we confined the moles using molar mass. There are 946.35 milliliters in every court and the density is 109 grams per milliliter. And we know that we need to multiply this fire percent 4.0 682 This gives us 105 0.7 grams of C six h, 807 to change two moles. We use the molar mass that we found a bug and we divide for everyone. Mole, there are 100 and 92.12 grams or our final answer is 0.549 moles of citric acid