Chemistry · Some Basic Concepts Of Chemistry · NEET
ppm means parts per million. Imagine you split the whole solution into 1,000,000 (one million) equal parts. ppm tells you how many of those parts are the solute. So 5 ppm means 5 parts of solute for every 1,000,000 parts of solution. It is just like percent, but percent is 'per hundred' and ppm is 'per million'.
ppm = (Number of parts of the component / Total number of parts of all components of the solution) x 10^6. This is equation 1.3 from NCERT. You multiply by 10^6 (one million) because you are counting parts out of a million, not out of a hundred.
When the solute is present in a very small (trace) amount, mass percent gives an awkward tiny number like 0.0005%. ppm turns it into an easy number like 5 ppm. NCERT says ppm is used 'when a solute is present in trace quantities', for example pollutants in water or air.
It can be both. Just like percentage, ppm can be expressed as mass-to-mass (w/w), volume-to-volume (v/v), or mass-to-volume (w/V). In NEET problems, ppm 'by mass' is the most common. Always read whether the question says 'by mass' or 'by volume'.
Percent is per hundred and ppm is per million. Million is 10,000 times bigger than hundred. So to go from ppm to percent, divide by 10,000. Example: 15 ppm = 15 / 10,000 = 0.0015%. To go from percent to ppm, multiply by 10,000.
Yes, for dilute water solutions. 1 litre of water is about 1000 g = 1,000,000 mg. So 1 mg of solute in 1 L means 1 part in a million parts by mass, which is 1 ppm. This shortcut (1 ppm approximately equals 1 mg/L) works because dilute water has a density near 1 g/mL. NCERT also notes pollutant concentration is often given in mg mL^-1 or ppm.
No. NCERT clearly states that mass %, ppm, mole fraction and molality are independent of temperature, while molarity depends on temperature. This is because temperature changes volume but not mass, and ppm by mass uses only masses.
In the NCERT chloroform example, 15 ppm by mass means 15 g of chloroform (CHCl3) is present in 10^6 g (one million grams) of the water sample. It is a very small, trace amount, which is why ppm is used instead of percent.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
ppm stands for parts per million. It is a concentration term that tells how many parts of a solute are present in one million (10^6) parts of the total solution. It is used for very small (trace) amounts.
ppm = (Number of parts of the component / Total number of parts of all components) x 10^6. Multiply the ratio by 10^6 because you are expressing parts out of a million.
No. ppm, along with mass percent, molality and mole fraction, is independent of temperature. Only molarity depends on temperature because volume changes when temperature changes.
Divide by 10,000. 15 ppm = 15 / 10,000 = 0.0015% by mass. This is because percent is per hundred and ppm is per million.
Yes, approximately. In dilute water solutions 1 litre weighs about 10^6 mg, so 1 mg of solute per litre is about 1 ppm by mass.
