Question

Which solutions have a concentration of $1M$ ?
i. $74$ grams of calcium hydroxide dissolved to make $1$ liter of solution.
ii. $74.5$ grams of potassium chloride dissolved to make $1$ liter of solution.
iii. $87$ grams of lithium bromide dissolved to make $1$ liter of solution.
A. i only
B. iii only
C. i and iii only
D. ii and iii only
E. i, ii and iii

Answer 1

Concentration refers to the amount of solute that is dissolved in the unit amount of the solution or the solvent. Concentration of a solution can be represented in many forms such as the amount of solute dissolved in a given mass or volume of solvent or the amount of solute present in a given amount (volume or mass) of solution.

Complete step by step answer:
From your chemistry lessons you have learned about the concentration of a solution and what it refers to. Concentration of a solution is defined as the quantity of the solute that is present in the particular quantity of solution or the solvent. There are many different methods to define the concentration of the solution such as Molarity, Molality, etc.
The most common unit among the concentration terms is molarity. It is very much important and useful for calculating the stoichiometry of the reaction in solution. It is defined as the number of moles of solute that is present in the $1$ litre of the solution. And it is given as:
$molarity(M)=\dfrac{moles(solute)}{litres(solution)}$ and $concentration(solution)=\dfrac{Amount(solute)}{Amount(solution)}$
All three solutions have a concentration of $1M,$
$74$ grams of calcium hydroxide dissolved to make $1$ liter of solution
The molar mass of calcium hydroxide is $74g/mol$ . Hence, $74$ grams of calcium hydroxide corresponds to $1$ mole. When 1 mole of solute is dissolved in $1L$ of solution, the concentration is $1\text{ }M.$
$concentration(solution)=\dfrac{74g}{\left( 74g/mol \right)\times \left( 1L \right)}$
concentration(solution)=1M
$74.5$ grams of calcium hydroxide dissolved to make $1$ liter of solution
The molar mass of calcium hydroxide is $74.5g/mol$ . Hence, $74.5$ grams of calcium hydroxide corresponds to $1$ mole. When 1 mole of solute is dissolved in $1L$ of solution, the concentration is $1\text{ }M.$
$concentration(solution)=\dfrac{74.5g}{\left( 74.5g/mol \right)\times \left( 1L \right)}$
concentration(solution)=1M
$87$ grams of calcium hydroxide dissolved to make $1$ liter of solution
The molar mass of calcium hydroxide is $87g/mol$ . Hence, $87$ grams of calcium hydroxide corresponds to $1$ mole. When 1 mole of solute is dissolved in $1L$ of solution, the concentration is $1\text{ }M.$
$concentration(solution)=\dfrac{87g}{\left( 87g/mol \right)\times \left( 1L \right)}$
concentration(solution)=1M

So, the correct answer is Option E.

Note: The concentration of a solution is a type of macroscopic property. It can be expressed in many forms such as both quantitatively and qualitatively. It can be qualitatively expressed as the dilute solution or the concentration solution and quantitatively it can be expressed as saturated or unsaturated.