Question

If 255 g of water has 10.0 g of NaCl dissolved into initially, how much NaCl must be added in order to raise the mass percent of NaCl by 10%?

Answer 1

original mass percent = (mass of salt/total mass)*100% = (10.0/[255+10.0])*100%

if we add some mass x of NaCl the equation becomes
([10.0 + x]/[255+10.0 + x])*100%

so if we want to increase the mass percent by 10% that means old mass % + 10% = new mass %, or in other words


(10.0/[255+10.0])*100% + 10% = ([10.0 + x]/[255+10.0 + x])*100%

solve for x