Answer:
6.8g of solute are needed
Explanation:
Percent by mass, (w/w%) is defined as the mass of solute in 100g of solution. A solution that is 3.4% contains 3.4g of solute in 100g of solution. That means to make 200g of solution are required:
200g solution * (3.4g solute / 100g solution) = 6.8g of solute are needed
