Ответ:
2%
Объяснение:
200 г =100%
4 г =?
200/100=2
4 г = 2%
Ответ: в 200 г песке 2% примесей
<span>а)Ba(OH)2+HCI=>BaCl(+)+H(OH)2(-)
</span><span>б)K2S+H2SO4=>K2SO4(0)+ H2S(0)
</span><span>в)BaCI2+MgSO4=>BaSO4(0)+MgCl2(0)
</span><span>г)NaNO3+MgCI2=>NaCl2(-)+MgNO3(+)
</span><span>д)AgNO3+AICI3=>AgCl3(2-)+AlNO3(2+)
</span><span>е)CaCO3+HCI=>CaCl(+)+HCO3(-)
</span><span>ж)Cu(OH)2+H2SO4=>CuSO4(0)+H2(OH)2(0)
</span><span>з)FeCI2+NaOH =>FeOH(+)+NaCl2(-)</span>
CaO + H2O = Ca(OH)2
P2O5 + H2O = 2HPO3
Na2CO3 = Na2O + CO2
CO2 + NaOH = NaHCO3
Fe + 2HCl = FeCl2 + H2
Na2CO3 + 2HCl = 2NaCl + CO2 + H2O
<span>Ca<span>(OH)</span>2</span> + CuCl2 =Cu(OH)2 + CaCl2
<span>2Fe<span>(OH)</span>3</span> = Fe2O3 + 3H2O
Fe + CuSO4 = FeSO4 + Cu
<span>К2СО3 + ВаСl2=ВаСО3 + 2КСl</span>
CH2CHO + O2 → 2 CHC3OOH;K2co3+ COOH= CH3OOH