a) 2NaHCO3 → Na2CO3 + H2O + CO2

​b) 84,0g NaHCO3 = 53,0g Na2CO3 + 9,0g H2O + m(CO2)

c) m(CO2) = m(NaHCO3) - [m(Na2CO3) + m(H2O )]

= 84,0 - (53,0 + 9,0) = 84,0 - 62,0 = 22,0 (g)

a) 3Fe + 2O2 to→to​→→  Fe3O4 

b)  CuSO4 + 2NaOH → Cu(OH)2 + Na2SO4

c) CaCO3 + 2HCl → CaCl2 + CO2 + H2O

d. 2K + 2H2O → 2KOH + H2

a) hóa trị - phân tử

b)  đơn chất - kí hiệu hóa học

a)\(\text{3x(x−1)−1+x=0}\)

=> \(3x\left(x-1\right)+\left(x-1\right)=0\)

=> \(\left(x-1\right)\left(3x+1\right)=0\)

=> \(x-1=0\) hoặc \(3x+1=0\)

=> \(x=1\) hoặc \(x=-\dfrac{1}{3}\)

b) \(x^2-9x=0\)

=> \(x\left(x-9\right)=0\)

=> \(x=0\) hoặc \(x-9=0\)

=> \(x=0\) hoặc \(x=9\)

a)\(x^2+25-10x\)=\(x^2-2\cdot5x+5^2\)=\(\left(x-5\right)^2\)

b)\(-8y^3+x^3\)=\(x^3-8y^3\)=\(x^3-\left(2y\right)^3\)=\(\left(x+2y\right)\left(x^2+x2y+4y^2\right)\)

a) \(\left(2x+1\right)^2\) = \(4x^2+4x+1\)

b) \(\left(a-\dfrac{b}{2}\right)^3\)=\(a^3-\dfrac{3}{2}a^3b+\dfrac{3}{2}ab^2-b^3\)