Question
(b) Potassium chloride can be made by reacting potassium with chlorine. The equation for the reaction is 2K+Cl_(2)arrow 2KCl Calculate the mass of potassium needed to make 1.492 g of potassium chloride. (Relative formula mass of potassium chloride=74.6) (Relative atomic mass of potassium=39.1) Show your working.
Answer
4.1
(191 Votes)
Preston
Elite · Tutor for 8 years
Answer
1. Calculate the number of moles of potassium chloride: 1.492 g / 74.6 g/mol = 0.02 moles2. Given the reaction's 1:1 ratio, also have 0.02 moles potassium.3. Mass of potassium = (0.02 moles K * 39.1 g/mol K) = 0.78 g
Explanation
In this question, you are asked to find the mass of the reactant potassium needed to produce 1.492 g of a product, in this case potassium chloride (KCl). The balanced chemical equation tells us that for every two molecules of KCl produced, two atoms of potassium (K) are needed.1. Firstly, there's a need to determine the number of moles of KCl that could be obtained. This requires dividing the mass of potassium chloride by its relative formula mass. Formula: no. of moles = mass/relative formula mass2. Realize that the reaction exhibits a 1:1 ratio in the balanced chemical equation. This implies that the number of moles for the potassium needed is the same as the number of moles for KCl since there's a 1:1 stoichiometric ratio between potassium and KCl, according to the given equation.3. Lastly, get the mass of the potassium i.e. multiply the relative atomic mass and calculate the mass of potassium. The formula is: mass = no. of moles x relative atomic massRemember, the overall aim is to help assess understanding of concepts relating to the realms of stoichiometry and molar mass calculation.