#### Answer

2.5 g

#### Work Step by Step

A 0.25% sucrose solution means that a 100. g solution contains 0.25 g $C_{12}H_{22}O_{11}$.
$\implies( 100\,g\times10=1000\,g= 1.0\,kg)$ solution contains $(0.25\,g\times10)$ $C_{12}H_{22}O_{11}$.
That is, the mass in grams of sucrose is= 2.5 g.