could someone please explain how i would work this out??
You need 100 ml of 50 mM NaH2PO4 (sodium dihydrogen
orthophosphate, Mw = 156)
• How much to weigh out?
To calculate the amount of NaH2PO4 you need to weigh out, you'll need to use the molecular weight of NaH2PO4, the desired concentration, and the desired volume.
First, convert the desired concentration from millimoles per liter (mM) to moles per liter (M), since the molecular weight is given in grams per mole. Divide the desired concentration by 1000 to convert mM to M. In this case, 50 mM NaH2PO4 is equal to 0.05 M NaH2PO4.
Next, multiply the desired concentration in moles per liter by the desired volume in liters to get the amount in moles. In this case, the desired volume is 100 ml, so the amount in moles would be 0.05 M x 0.1 L = 0.005 moles.
Finally, multiply the amount in moles by the molecular weight of NaH2PO4 to get the amount in grams. In this case, the molecular weight of NaH2PO4 is 156 g/mol. So the amount to weigh out would be 0.005 moles x 156 g/mol = 0.78 grams.
Therefore, you would need to weigh out 0.78 grams of NaH2PO4 to obtain 100 ml of 50 mM NaH2PO4 solution.