Which substance yields hydroxide ion as the only negative ion in aqueous solution?

Missing question:
a. Mg(OH)2.
b. CH3Cl.
c. MgCl2 .
d. C2H4(OH)2.
Answer is: a. Mg(OH)₂.
An Arrhenius base is a substance that dissociates in water to form hydroxide ions (OH⁻).
In this example magnesium hydroxide is an Arrhenius base:
Mg(OH)₂(aq) → Ba²⁺(aq) + 2OH⁻(aq).
CH₃Cl and C₂H₄(OH)₂ are organic compound and will not give hydroxide ions in water, MgCl₂ is neutral salt and it will give Cl⁻ ions.

-

12.41 g

Explanation: -

Mass of CO₂ = 42 g

Molar mass of CO₂ = 12 x 1 + 16 x 2 = 44 g / mol

Number of moles of CO₂ =

= 0.9545 mol

The balanced chemical equation for this process is

2C₆H₆ + 15O₂ → 12CO₂ + 6H₂O

From the balanced chemical equation we see

12 mol of CO₂ is produced from 2 mol of C₆H₆

0.9545 mol of CO₂ is produced from

= 0.159 mol of C₆H₆

Molar mass of C₆H₆ = 12 x 6 + 1 x 6 =78 g /mol

Mass of C₆H₆ =Molar mass x Number of moles

= 78 g / mol x 0.159 mol

= 12.41 g