Answer:
0.12 M
Explanation:
Step 1: Write the balanced equation
NaOH + HCl ⇒ NaCl + H₂O
Step 2: Calculate the reacting moles of NaOH
10 mL of a 0.30 M NaOH solution react.

Step 3: Calculate the reacting moles of HCl
The molar ratio of NaOH to HCl is 1:1. The reacting moles of HCl are 1/1 × 3.0 × 10⁻³ mol = 3.0 × 10⁻³ mol.
Step 4: Calculate the concentration of HCl
3.0 × 10⁻³ mol of HCl are in 25 mL of solution.

The mole fraction of HNO3 is 0.225
<u>Explanation:</u>
<u>1.</u>Given data
Density = 1.429 /ml
Mass% = 63.01 g HNO3 / 100g of solution
The mass of 63.01 g is in 100 / 1.142 /ml of solution
Or 63.01 g in 55.7 mL
Molarity = 15.39 moles / L
Mass of water in 100g = 100 - 63.01=36.99 g
So 63.01 grams in 36.99 grams of water
So mass of HNO3 in 1000grams of water = 63.01* x 1000 / 36.99 = 1703
Moles of HNO3 in 1000g = 1703 / 63.01 = 27.03 moles
Molality = 27.03 molal (mole / Kg)
Mole fraction = Mole of HN03 / Moles of water + mole of HNO3
Mole of water = 62/ 18 = 3.44
Moles of HNO3 = 63.01 / 63.01 = 1.000
Mole fraction = 1.000 / 3.44 + 1.000 = 0.225
The mole fraction of HNO3 is 0.225
10 decigrams are equivalent to 1 gram, so 2,100 grams are equivalent to 2100 x 10. This makes 21,000.