Question

_____ g of MnSO4 H2O are needed to prepare a solution of 100.00 mL of 0.700 M MnSO4 Dilution of 1.00mL of 0.7 M MnSO4 solution to 20.00 mL aqueous solution gives a new concentration of _____ M .

Answer 1

You want 0.700 M MnSO4 so you want 0.700 moles MnSO4 in 1 L of soln. For 100 mL, you will want 0.1 of that. You want to know grams and moles = grams/molar mass. You know moles and you know molar mass; calculate grams.
Then on the dilution, the easy way is to do it this way.
0.7 M x 1.00/20.00 = ?? but sometimes the easiest to understand is to change 0.7 M x 0.001 L (that's 1 mL) to moles, then put that number of moles in 20 mL, divide moles/L to convert to M. You should get the same answer.