1. I have 2% NaCl solution. From this I want to prepare a solution to contain 0.1 g of the sodium compound in 2 mL of water.

Question

Thanks

Answer 1

2% NaCl means 2g NaCl/100 ml solution.
0.1g NaCl/2 mL is a 5% solution; therefore, this is not a dilution problem but a concentration problem. So you need to boil away x mL H2O to make the final volume what to make 5%.
2%*(100/x) = 5%
x = ?