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When you are doing a large construction project, you have a good idea of how many nails you will need (lots! When you go to the hardware store, you don't want to sit there and count out several hundred nails.You can buy nails by weight, so you determine how many nails are in a pound, calculate how many pounds you need, and you're on your way to begin building.
\[2 \ce \left( g \right) 3 \ce \left( g \right) \rightarrow 2 \ce \left( g \right) 2 \ce \left( g \right)\] What mass of oxygen gas is consumed in a reaction that produces \(4.60 \: \text \: \ce\)?
Solution: Use the mole ratio to convert from \(\text \: \ce\) to \(\text \: \ce\). This will be done in a single two-step calculation.
From this, you are to determine the mass of another substance that will either react with or be produced from the given substance.
\[\text \rightarrow \text \rightarrow \text\] The moles of the given substance are first converted into moles of the unknown by using the mole ratio from the balanced chemical equation.
The mass of the impure sample is 0.1250 kg and it is composed of 87.00% (by mass) calcium carbonate.
Before Chris can use this calcium carbonate in a chemical reaction, Chris needs to know the amount, in moles, of calcium carbonate present in this sample.Let’s start really basic and ask how many moles there are in a certain number of things (atoms, ions, et al.). We know that there are 12 bagels per dozen, so we divide 36 by 12 to get 3 dozen. To find out the number of moles, divide the number of things by the number of things per mole (the Avogadro Constant) to get the number of moles.The mole is, in essence, just a number, just how we call 12, “a dozen”. The mole is used to take gargantuan numbers and make them into a more manageable size.where mass is in grams and the molar mass is in grams per mole.Moles to Mass Calculation We can use the above equation to find the mass of a substance when we are given the number of moles of the substance.Calculate the amount of calcium carbonate in moles present in this impure sample of calcium carbonate.Solving the Problem using the Sto PGo PS model for problem solving: ) = 100/87 × 100 = 115 g = 0.115 kg Since this approximate value for the mass of the sample is about the same as the mass of sample given in the question, we are reasonably confident that our answer is correct.Example 12.3.1 Tin metal reacts with hydrogen fluoride to produce tin (II) fluoride and hydrogen gas according to the following balanced equation.\[\ce \left( s \right) 2 \ce \left( g \right) \rightarrow \ce \left( s \right) \ce \left( g \right)\] How many moles of hydrogen fluoride are required to react completely with \(75.0 \: \text\) of tin?While the mole ratio is ever-present in all stoichiometry calculations, amounts of substances in the laboratory are most often measured by mass.Therefore, we need to use mole-mass calculations in combination with mole ratios to solve several different types of mass-based stoichiometry problems.