Verified answer

Exercice 1

1) Cm = m/V

Cm = 2/5

Cm = 0,4 g/L

2) Calculons la masse molaire de NaOH

M(NaOH) = M(Na) + M(O) + M(H)

M(NaOH) = 23 + 16 + 1

M(NaOH) = 40 g/mol

C = Cm / M

C = 0,4/40

C = 0,01 mol/L

3)

m = n×M et n = C×V

m = C×V×M

m = 0,04 × 1,5 × 40

m = 2,4 g

Exercice 2

1)

Calculons la masse molaire de NaOH

M(NaOH) = M(Na) + M(O) + M(H)

M(NaOH) = 23 + 16 + 1

M(NaOH) = 40 g/mol

C = Cm / M

C = 2,5/40

C = 0,0625 mol/L

C = 6,3.10⁻² mol/L

2)

m = Cm × V

m = 2,5 × 2,5

m = 6,25

m = 6,3 g ( à 2 chiffres significatifs)

n = m/M

n = 6,3/40

n = 0,15625

n = 1,6.10⁻¹ mol (à 2 chiffres significatifs)