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Explain the term molality

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प्रश्न

Explain the term molality

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उत्तर

Molality is the number of moles of solute present in 1 kg of solvent. It is denoted by m.
Molality is expressed as follows:
Molality (m) = `"Number of moles of solute"/"Mass of solvent in kilograms"`

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पाठ 2: Introduction to Analytical Chemistry - Exercises [पृष्ठ २३]

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बालभारती Chemistry [English] Standard 11 Maharashtra State Board
पाठ 2 Introduction to Analytical Chemistry
Exercises | Q 2. (G)(c) | पृष्ठ २३

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Calculate the amount of carbon dioxide that could be produced when 2 moles of carbon are burnt in 16 g of dioxygen.


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A sample of drinking water was found to be severely contaminated with chloroform, CHCl3, supposed to be carcinogenic in nature. The level of contamination was 15 ppm (by mass).

  1. Express this in percent by mass.
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Why does the molarity of a solution depend upon temperature?


Solve the following problem:

Write the following number in ordinary decimal form:

43.71 × 10−4


Solve the following problem:

Write the following number in ordinary decimal form:

14.3 × 10−2


Solve the following problem:

Perform the following calculation. Round off your answer to two digits.

`33/(9.00xx10^-4)`


Perform each of the following calculations. Round off your answers to three digits.

(3.26104) (1.54106)


Solve the following problem:

Perform the following calculation. Round off your answer to three digits.

`(8.94xx10^6)/(4.35xx10^4)`


Solve the following problem:

Perform the following calculation. Round off your answer to three digits.

`((9.28xx10^9)(9.9xx10^-7))/((511)(2.98xx10^-6))`


A 1.000 mL sample of acetone, a common solvent used as a paint remover, was placed in a small bottle whose mass was known to be 38.0015 g.
The following values were obtained when the acetone-filled bottle was weighed: 38.7798 g, 38.7795 g and 38.7801 g. How would you characterise the precision and accuracy of these measurements if the actual mass of the acetone was 0.7791 g?


Solve the following problem:

Your laboratory partner was given the task of measuring the length of a box (approx 5 in) as accurately as possible, using a metre stick graduated in milimeters. He supplied you with the following measurements:

12.65 cm, 12.6 cm, 12.65 cm, 12.655 cm, 126.55 mm, 12 cm.

Give your reason for rejecting each of the others.


Solve the following problem:

What weight of calcium oxide will be formed on heating 19.3 g of calcium carbonate?
(At. wt.: Ca = 40; C = 12; O = 16)


When light is passed through water containing a few drops of milk, it shows a bluish tinge. This is due to the ______ of light by milk and the phenomenon is called ______. This indicates that milk is a ______ solution.


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(ii) Name the technique used by the child.

(iii) Suggest one more application of this technique.


Calculate the mass of sodium sulphate required to prepare its 20% (mass percent) solution in 100g of water?


What will be the molarity of a solution, which contains 5.85 g of NaCl(s) per 500 mL?


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If the concentration of glucose \[\ce{(C6H12O6)}\] in blood is 0.9 g L–1, what will be the molarity of glucose in blood?


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(ii) \[\ce{0.5 mol of KCl in 200 mL of solution}\]

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(iv) \[\ce{20 g of KOH in 200 mL of solution}\]


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Physical quantity Unit
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(iv) Molality (d) Unitless
(v) Pressure (e) mol L–1
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(vii) Density (g) mol kg–1
(viii) Mass (h) Nm–1
  (i) kg

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(Given: Atomic weights are H, 1u; C, 12u; O, 16u)


Molarity is ______.


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