Question:

The mass of $CaCO_3$ is required to react with 25 mL of 0.75 M HCl is

Updated On: Jul 7, 2022
  • 0.94 g
  • 9.4 g
  • 0.094 g
  • 0.49 g
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The Correct Option is A

Solution and Explanation

$CaCO_{3}+2HCl \to CaCl_{2}+CO_{2}+H_{2}$ $25\, mL$ of $0.75\, M\, HCl$ $=\frac{25}{100}L\times (0.75\,mol\,L^{-1})$ $= 0.01875 \,mol$ Moles of $CaCO_{3}$ required $=\frac{\text{Moles of HCl}}{2}$ $=\frac{0.01875}{2}=9.375\times10^{-3}\,mol$ Mass of $CaCO_{3}$ required $=9.375\times10^{-3}\,mol\times 100\,g\,mol^{-1}$ $=0.9375\,g=0.94\,g$
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Concepts Used:

Mole Concept

In the field of chemistry, a mole is defined as the amount of a substance that contains exactly 6.02214076 * 1023 β€˜elementary entities’ of the given substance.

The number 6.02214076*1023 is popularly known as the Avogadro constant and is often denoted by the symbol β€˜NA’. The elementary entities that can be represented in moles can be atoms, molecules, monoatomic/polyatomic ions, and other particles (such as electrons).

For example, one mole of a pure carbon-12 (12C) sample will have a mass of exactly 12 grams and will contain 6.02214076*1023 (NA) number of 12C atoms. The number of moles of a substance in a given pure sample can be represented by the following formula:

n = N/NA

Where n is the number of moles of the substance (or elementary entity), N is the total number of elementary entities in the sample, and NA is the Avogadro constant.

The word β€œmole” was introduced around the year 1896 by the German chemist Wilhelm Ostwald, who derived the term from the Latin word moles meaning a β€˜heap’ or β€˜pile.

The mole concept refers to the atomic mass of a mole that is measured in grams. The gram atomic mass of an element is known as a mole. The mole concept combines the mass of a single atom or molecule in a.m.u. to the mass of a large group of comparable molecules in grams. Atomic mass is the mass of a single atom, whereas molecular mass is the mass of a group of atoms. 

The Formula of Mole Concept

The number of units that make up a mole has been calculated to be 6.022 Γ—10Β²Β³. The fundamental constant is also known as Avogadro's number (NA) or Avogadro constant. This constant is appropriately represented in chemistry using an explicit unit termed per mole.

Number of Moles = (Mass of the Sample)/(Molar Mass)

Read More: Mole Fraction