Giúp với ạ mk đg cần gấp . CẢM ƠN NHIỀU

7.

`150ml=0,15l;100ml=0,1l;50ml=0,05l`

`n_{HCl}=0,05.x(mol)`

`n_{Ba(OH)_2}=0,15.0,2=0,03(mol)`

`n_{HCl}=0,1.0,1=0,01(mol)`

Dễ thấy `A` chứa `Ba(OH)_2` dư

`2HNO_3+Ba(OH)_2->Ba(NO_3)_2+2H_2O`

`0,05x->0,025x(mol)`

`->n_{Ba(OH)_2(du)}=0,03-0,025x(mol)`

`2HCl+Ba(OH)_2->BaCl_2+2H_2O`

`0,01->0,005(mol)`

`->0,03-0,025x=0,005`

`->x=1`

`Vậy `x=C_{M\ HNO_3}=1(mol // l)`

8.

`n_{Na_2O}={155}/{62}=2,5(mol)`

`Na_2O+H_2O->2NaOH`

`2,5->`   `2,5->`     `5(mol)`

`->m_{dd\ spu}=155+145=300(g)`

`->C\%_{NaOH}={5.40}/{300}.100\%\approx 66,67\%`