An aqueous solution has a mass of 490 grams containing 8.5 × 10-3 gram of calcium ions. the concentration of calcium ions in this solution is

1. 4.3 ppm
2. 8.5 ppm
3. 17 ppm
4. 34 ppm

To solve the concentration, it is equal to the mass of the calcium ions divided by the total mass of the solution.
C = mass of ions / mass solution
C = ( 8.5 x 10 ^-3 g ) / 490 g
C = 1.7 x 10^-5
since the choices are in ppm, multiply it by 10^6
C = (1.7 x 10^-5 ) 10^6
C = 17 ppm

The independent variable is the type of music.the dependent variable is the pulse rate.the intervening variable is the age of the subject.if the mother does not like rock, her pulse is likely to not increase.the same might be true for the sister.the friend may like rap and gets excited.to establish cause/effect relationship, all of the subjects must be consistent.hope i .