Question

How many grams of solid Na2CO3 are required to neutralize exactly 2 liters of an HCI solution of pH 2.0?

Answer 1

Answer:

The answer is 1.06g.

Explanation:

Analysis of question:

1. Identify the information in the question given.

• volume of HCl is 2 dm3
• pH of HCl is 2.0

2. What the question want?

• mass of Na2CO3 is ?(unknown)
• 3. Do calculation.
• 1st-Write a balanced chemical equation:

Na2CO3 + 2HCl (arrow) 2NaCl + H20 + CO2

• 2nd-Determine the molarity of HCl with the value of 2.0.

pH= -log[H+]

2.0= -log[H+]

log[H+]= -2.0

[H+]= 10 to the power of negative 2(10-2)

=0.01 mol dm-3

molarity of HCl is 0.01 mol dm-3

• 3rd-Find the number of moles of HCl

n=MV

=0.01 mol dm-3 × 2 dm3

=0.02 mol of HCl

• 4th-Find the second mol of it.

Based on the chemical equation,

2.0 mol of HCl reacts with 1.0 mol of Na2CO3

0.02 mol of HCl reacts with 0.01 mol of Na2CO3

Na2CO3>a=1 mol

2HCl>b=2 mol

• 5th-Find the mass of it.

mass= number of mole × molar mass

g=0.01 × [2(23)+ 12+ 3(16)]

g=0.01 × 106

# =1.06 g.