October 10, 2015

Homework Help: chemistry

Posted by Stacy on Wednesday, December 8, 2010 at 9:37pm.

Determine the number of bromide ions in solution when 4.23 g of magnesium bromide and 1.21 g of potassium bromide are dissolved in 120mL of water.

Please explain not sure how to even start this problem, thanks!

chemistry - DrBob222, Wednesday, December 8, 2010 at 7:57pm
Convert 4.23 g MgBr2 to moles and multiply that by 2 to obtain moles Br^- from MgBr2. moles = grams/molar mass.

Convert 1.21 g KBr the same way. Add the moles Br^- together to obtain total moles, then remember that 1 mole of Br^- ions will contain 6.022E23 ions.

chemistry - Stacy, Wednesday, December 8, 2010 at 8:58pm
4.23g MgBr2 Moles= grams/molar mass

4.23/184.113 = 0.023 moles

1.21g KBr Moles= grams/molar mass

1.21/119.002 = 0.033

and than what? I add those two #'s together? 0.033 + 0.023 = 0.033

and I dont know what you mean by 1 mole of Br- ions will contain 6.022e23 ions where did you get that info?


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