Question

Experiment 8 Conservation of Mass kussion: action: 170 Mole wt. g/mol Aqual the combined masses of all the reactants that were initially present. Furthermore, we fter any chemical reaction, the total mass of new products and any left over reactants) will a predict the mass of each product that will be formed if we know the molecular weight or the formula (from which we can predict the molecular weight). As an example, consider the dissolve the two substances in water, mix the solutions and then compare the masses (weights) of To confirm the identification of each product, we will perform a chemical test for AgNO3 + KBr → AgBr + KNO3 119 188 101 289g 289g the products with those of the reactants. The reaction is: carbonate and a flame test for the strontium. Total weight If we weigh 170 grams of AgNO3 and dissolve it in water and do the same for 119 grams of KBr, we can combine the two solutions and cause the reaction to occur. A white precipitate iams, which settles to the bottom of the beaker if left undisturbed, because one of the two products, either AgBr or KNO3, is water insoluble. The other is soluble in water and we are not stating beforehand which is which. Then, suppose we filter the solution, collecting the precipitate on the filter paper and the solution in a beaker. After the precipitate has dried and the water boiled from the solution, we may determine the weights of each solid. If the precipitate has a mass of 188 grams (or near this), it can be positively identified as the silver bromide. Conversely, if it has a mass of 101 frams, it must be potassium nitrate. The other solid will show the alternate mass. In this experiment, we will not actually use silver nitrate because of its cost. Instead, we will use strontium nitrate Sr(NOx), and potassium carbonate (K,CO2) and the quantities will be scaled down by a factor of 100. But the idea is the same as in our other example; that is, we will + 2 KNO Sr(NO3)2 + K2CO3 → SrCoz