AS level chemistry question.. titrations HELP PLEASE

Work out the number of moles of Sulphuric Acid in the solution (using the equation Moles= Volume x Concentration, and remembering to put the concentration in dm^3). Then write a balanced equation, from which it should become apparent how many moles of Sodium Carbonate are required to react with this number of moles. Then multiply this by 10 to get the number of moles in the full 250cm^3. Then use the equation Mass= Molar Mass x Number of moles, which will give you the mass of Sodium Carbonate in the soda crystals. Then divide this by 5.125, and multiply by 100, to get the Sodium Carbonate in the crystals.

why multiplying 10 get your no. of moles in full 250cm³ solution

Imagine the original 250 cm3 solution had 10 mol in it and you took out 25 cm3 of that solution, it would contain 1 mol.

Now imagine you took 25 cm3 out of a 250 cm3 solution and you found that the 25 cm3 had I don't know 0.0125 mol in. Surely the 250 cm3 would contain 0.125 mol?!?

Three words : 11 years ago

11 isn't a word and the thread is only ten years old?

I was replying to Nan8903, who was asking a Q about a thread they have somehow found. Perhaps they were doing a past paper with this Q and googled "5.125 g of washing soda crystals" and found this thread.

I usually say something along the lines of "let the dead rest", but was too sleepy this morning to be sarcastic. When people reply to threads giving solutions to an OP from many many years ago, then they get both barrels. My favorite is when people give solutions that are wrong to threads that already have the correct solution posted.