Answer;
Molarity = 0.25 M
Explanation;
Molarity is given by moles/Liter.
First we find moles:
Number of moles = Mass /molar mass
= (10.7g NH4Cl)/(53.5g/mol NH4Cl)
= 0.200 moles NH4Cl
Then we convert to liters:
= (800mL)*(1L/1000mL) = 0.800L
Therefore; molarity = 0.2moles/0.8L
= 0.25M