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Difficulty: EasyAcid-Base Titrations, Indicators, and Volumetric Calculations

A standard solution is prepared by dissolving 4.0 g4.0\text{ g} of pure solid sodium hydroxide (NaOH\text{NaOH}) in distilled water to make 1.0 dm31.0\text{ dm}^3 of solution. What is the molar concentration of this solution? [Na=23, O=16, H=1][\text{Na} = 23,\text{ O} = 16,\text{ H} = 1]

  1. A
    4.00 mol dm−34.00\text{ mol dm}^{-3}
  2. 0.10 mol dm−30.10\text{ mol dm}^{-3}Answer
  3. C
    0.40 mol dm−30.40\text{ mol dm}^{-3}
  4. D
    160 mol dm−3160\text{ mol dm}^{-3}

Answer

The molar concentration of the sodium hydroxide solution is 0.10 mol dm−30.10\text{ mol dm}^{-3}.
The solution containing 4.0 g4.0\text{ g} of NaOH\text{NaOH} per dm3\text{dm}^3 is converted to molar concentration by dividing by the molar mass of NaOH\text{NaOH} (40 g mol−140\text{ g mol}^{-1}), yielding 0.10 mol dm−30.10\text{ mol dm}^{-3}.

Step-by-Step Solution

1
Calculate the molar mass of sodium hydroxide (NaOH\text{NaOH}).
Molar mass =23+16+1=40 g mol−1= 23 + 16 + 1 = 40\text{ g mol}^{-1}.
Molar mass is required to convert mass to moles.
2
Calculate the concentration in mol dm−3\text{mol dm}^{-3} by dividing mass concentration by molar mass.
\text{Molar concentration} = \frac{4.0\text{ g dm}^{-3}}{40\text{ g mol}^{-1}} = 0.10\text{ mol dm}^{-3}.
Molar concentration is defined as moles of solute per unit volume of solution in dm3\text{dm}^3.

Key Concept

Conversion from mass concentration (g/dm³) to molar concentration (mol/dm³)
Estimated Time:45s
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Topics

Acid-Base Titrations, Indicators, and Volumetric Calculations

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