#### • Class 11 Physics Demo

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#### • how to dilute phosphoric acid

Question:How many mL of concentrated nitric acid (HNO3, 16.0 M) should be diluted with water in order to make 2.00 L of 2.00 M solution? a. 250. mL b. 125 mL c. 32.0 mL d. 500. mL e. 62.5 mL

Answers:Concentration 1 * Volume 1 = Concentration 2 * Volume 2 V1 = C2 * V2/ C1 V1 = 2.00 mol/L * 2.00 L/16.0 mol/L = 0.25 L = 250 ml

Question:In dilute nitric acid, HNO3, copper metal dissolves according to the following equation. 3Cu(s) + 8HNO3(aq) 3Cu(NO3)2(aq) + 2NO(g) + 4H2O(l). How many moles of HNO3 are needed to dissolve 67.27 g of Cu according to this equation? *The answer I got was 177.8 grams HNO3?

Answers:It asks for how many moles of HNO3 you need...you found the mass. from the equation we see that for 3 mol of Cu that react we need 8 mol of HNO3 to react. therefore for every 1 mol of Cu we get 8/3 mol of HNO3. the molar mass of Cu is 63.54 so we divide 67.27 g Cu/ 63.54 g/mol and we get 1.06 mol Cu. so the mol of HNO3 that react needs to be (8/3)*1.06 = 2.83 mol of HNO3. If you convert the moles of HNO3 to grams of HNO3 then you should get your answer of 177.8 or there about. The question asks for moles though.

Question:I've got 25% how do I concentrate it to a higher concentration?

Answers:If you distill the nitric acid solution, it will form an azeotrope with water. The concentrated nitric acid of commerce consists of the maximum boiling azeotrope of nitric acid and water. Technical grades are normally 68% HNO3, (approx 15 molar). This occurs when the boiling temperature is 120.5 C. Beware!!!, This is extremely dangerous and must only be attempted in properly equiped laboratories, with proper safety equipment in use. It is definitely not something that you should try to do at home.

Question:Doing a lab for AP Chem and this question has stumped me. We were finding out how to determine the mass of silver in an alloy and this is during the filtration process. Sorry if it is too vague but help would be great!

Answers:hmmm Since ur NItric acid in water will be dilute, and Silver chloride is insoluble in many solutions...maybe u should use a more concentrated NItric acid, if u want to dissolve the chloride. Have u checked into the solubility of Silver Chloride in Acidic solutions?