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# AS Parts per million calculation Watch

1. The data on a 50 g tube of toothpaste states that it contains
“1450 ppm fluoride”; ppm means “parts per million” i.e. therewould be 1450g of fluoride ions in 106 (1,000,000)g of toothpaste.Use the following headings to work out the concentration ofsodium fluoride in the toothpaste. The density of the toothpaste is1.6 g cm–3.
Mass of fluoride ions in the 50 g tube I know that the answer is;
(1450/1000000) x 50

but i don't understand how. This is easy question but I don't understand how 1450/1000000 = mass of fluorine per gram of toothpaste. I understand all the remaining parts of the question

Can someone explain how to do this question?
2. (Original post by ozmo19)
The data on a 50 g tube of toothpaste states that it contains
“1450 ppm fluoride”; ppm means “parts per million” i.e. therewould be 1450g of fluoride ions in 106 (1,000,000)g of toothpaste.Use the following headings to work out the concentration ofsodium fluoride in the toothpaste. The density of the toothpaste is1.6 g cm–3.
Mass of fluoride ions in the 50 g tube I know that the answer is;
(1450/1000000) x 50

but i don't understand how. This is easy question but I don't understand how 1450/1000000 = mass of fluorine per gram of toothpaste. I understand all the remaining parts of the question

Can someone explain how to do this question?
1450/10^6 is not the mass of fluorine per gram specifically, it's the amount of fluoride per amount of toothpaste. So if we talk about it in mass terms, as you did at the beginning, there would be 1450(mass units) per 10^6(mass unit) of fluoride. So when you divide them, you get the ratio of fluoride to toothpaste (which is essentially what ppm means in the first place)
Multiplying it by the 50g will therefore give you the mass of fluoride, in grams, in the toothpaste.
Does that make sense? Not sure if I just repeated myself without actually explaining

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