94.6 g. You must use 94.6 g of 92.5 % H_2SO_4 to make 250 g of 35.0 % H_2SO_4.
We can use a version of the dilution formula
m_1C_1 = m_2C_2
where
m represents the mass and
C represents the percent concentrations
We can rearrange the formula to get
m_2= m_1 × (C_1/C_2)
m_1 = 250 g; C_1 = 35.0 %
m_2 = ?; _____C_2 = 92.5 %
∴ m_2 = 250 g × (35.0 %/92.5 %) = 94.6 g
