Lithium Cocentration Question

Question

The lithium concentration in serum taken from a patient being treated with lithium for manic-depressive illness was analyzed using flame emission spectroscopy. A sample of the serum gave a reading of 305 units for the intensity of the 671 nm red emission line. Then, 1.00 mL of a 11.31 mM lithium standard was added to 9.00 mL of serum. This spiked serum gave an intensity reading of 789 units at the 671 nm emission line. What is the original concentration of Li+ in the serum?

Li+ =. units mM

how would I solve for the concentration?

Answer 1

1.00mL(11.31mM Li+)=10mL(XmM Li+)

so... x=1.131mM Li+ in spiked sample

Unknown sample=305 units

Spiked sample= 789 units

take difference in reading 789-305=484

1.131 mM Li+=484 units

484units/305 units=1.131mM Li+/X mM Li+

x=0.826 mM Li+ in original sample