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# examples of molarity and molality

Answers:ur ans is correct.no need more explanation.

Question:What happens to molarity, molality, and concentration of a solution when more solute is added? What happens when more solvent is added?

Answers:When more solute is added M , m and concentration of the solution increase When more solvent is added M , m and concentration decrease

Question:1. A bottle of phosphoric acid is labeled "85.0% H3PO4 by mass; density = 1.680 g/cm3." Calculate the MOLARITY of phosphoric acid in the solution? 2. A bottle of phosphoric acid is labeled "85.0% H3PO4 by mass; density = 1.680 g/cm3." Calculate the MOLALITY of phosphoric acid in the solution?

Answers:formula: M=mol/L know: 1 cm^3=1 L step 1: assume % is g step 2: find mol, start with 85 g, go to mol step 3: find L, start with 85 g, go to cm^3, go to L step 4: use M eqn and solve formula: m=mol/kg know: 1 kg=1000 g step 1: find g solute, start with 85 g, go to mol, go to g step 2: g obtain in step 1 subtract from g sln density which gives you g solvent step 3: g to kg step 4: use m eqn and solve good luck.

Question:The electrolyte in a car battery is a 3.75 M sulfuric acid solution with a density of 1.23 g/mL. i'm completely lost on how to find mass percent, normality, and formality, and i still don't completely understand the difference between molarity and molality.

Answers:Molarity= moles of solute/L of solution Molality=moles of solute/kg of solvent So, first let's figure out the mass percent: (which would be grams of solute/grams of solution multiplied by 100) You have 3.75M sulfuric acid. M=Mol Sulfuric Acid/L solution To make life easier, let's assume you have 3.75mol sulfuric acid in 1L of solution, which would give us 3.75M To find the amount of grams of sulfuric acid that you have, multiply the moles by the molecular weight. So: 3.75 mol * 68.03 g (molecular weight): About 255 grams. To find out how many grams of solution, convert the amount of solution in liters to grams using the density. So, we assumed we had 1L of solution. Convert 1L to mL (because the density is in g/mL): 1L * 1000 mL/1L= 1000mL solution So density=mass/volume. Plug in the information: 1.23 g/mL = mass/1000mL 1.23g/mL * 1000mL=1230 grams solution. So, mass percent= (255 grams H2SO4/1230 grams solution)*100%=20.7% Now let's calculate the molality: Molality= moles of solute/kg of solvent So, we already assumed that there are 3.75 mol H2SO4 in the solution, so we have the moles solute. To determine the amount of solvent: -We know there are 255g solute in the solution and 1230 grams in total. And we know, Solute + Solvent = Solution. So plug in, and solve for the solvent: 255g + Solvent = 1230g Solvent=1230g-255g Solvent=975g Now, we have to convert that to kg by dividing by 1000 (because molality is in kg). So to recap: We have 3.75 mol H2SO4 and .975 kg Solvent. Thus, the molality of the solution is: mol solute/kg solvent= 3.75 mol/.975 kg= 3.85m Ok, so for normality: n mol equivalent of solute/L solution I found the following on the internet (because I find the concept difficult to explain: "Normality, N, is similar to molarity, moles of solute per liter of solution. However, instead of the entire solute, the normality is based on the number of moles of the active part of the solute, called a chemical equivalent. For an acid, the chemical equivalent is the number of moles of H+1 ion. For a base, the chemical equivalent is the number of moles of OH-1 ions. For an oxidation-reduction solution, the chemical equivalent is the number of moles of electrons transferred. The normality of hydrochloric acid, HCl, is the same as the molarity of hydrochloric acid, because there is one mole of H+1 ions for every one mole of hydrochloric acid. The normality of sulfuric acid, H2SO4, is twice the molarity because there are two moles of H+1 ions per mole of sulfuric acid. The advantage to using normality is that it gives an effective concentration (3M sulfuric acid is twice as acidic as 3M hydrochloric acid this is clear if they are labeled 6N and 3N, respectively)." Therefore, the normality for H2SO4 will be twice the molarity. 3.75*2= 7.50 N I don't remember how to calculate formality, but I think it is 3.75 F because H2SO4 is not an ionic compound. This paragraph from the website I cited helped: Formality, F, is the number of formula weight units of solute per liter of solution. Remember that one mole of a compound has a mass equal to the formula weight in grams. The number of formula weight units is equal to the number of moles for molecular substances. The purpose of formality is to distinguish the number of moles of a compound from the number of moles of ions in solutions of ionic compounds or weak electrolytes. I hope I've helped a little! Good luck!