m (salt) = 170 g
w% (salt) = 42%
V (H2O) = 40 ml
w% (salts in the final solution) -?
1) Find the mass of salt in the originally given solution:
m (salt) = 170 g * 0.42 = 71.4 g;
2) Find the mass of added water:
m (H2O) = p * V = 1 g / ml * 40 ml = 40 g;
3) Find the mass of the solution after adding water:
m (solution) = 170 g + 40 g = 210 g;
4) Find the mass fraction of salt in the resulting solution:
w% (salt) = m (salt): m (solution) * 100% = 71.4 g: 210 g * 100% = 34%.
Answer: w% (salt) = 34%.
One of the components of a person's success in our time is receiving modern high-quality education, mastering the knowledge, skills and abilities necessary for life in society. A person today needs to study almost all his life, mastering everything new and new, acquiring the necessary professional qualities.