Asolid sample contains about 200ppm (w/w) of ca. how many mg of sample must be dissolved in 100ml in order to give a solution that is about 1ppm (w/v) of ca after dilution?

We need to add mg

Explanation:

Remember first:

To calculate this mass, we need to calculate the concentration as follows:

Here we have the concentration of the sample in terms of x, being x the mg needed to have a solution of 1ppm (w/v). Therefore, we solve the system as follows:

Finally we need mg of sample to have a Ca concentration of 1ppm (w/v) in the final solution.