Can someone help me to answer this correctly, please, and explain it. Please answer these 3 short questions, I don't have more money to buy more questions. These 3 questions are different.

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A stock solution of Pb(CN)2 is available to prepare solutions that are more dilute. Calculate the volume, in mL, of a 2.0-M solution of Pb(CN)2 required to prepare exactly 250mL of a 0.870M solution of Pb(CN)2. You wish to make a 0.306M nitric acid solution from a stock solution of 6.00M nitric acid. How much concentrated acid must you add to obtain a total volume of 175mL of the dilute solution? In the laboratory you dilute 4.01mL of a concentrated 12.0M perchloric acid solution to a total volume of 150mL. What is the concentration of the dilute solution? M