Question

Can someone show me step my step solution to this question... A mixture of NaCl and NaBr has a mass of 2.00 g and contains 0.75 g of Na. What is the mass of NaBr in the mixture?

Answer 1

Molar mass of NaCl = 58.44 g/mol

molar mass of NaBr =102.89 g /mol

mass of total mixture = 2.00 g

molar mass of Na =23g/mol

moles of Na present in the mixture = 0.75 /23 = 0.0326 mol

so the mixture must contain total of Cl + Br moles = 0.0326

mass of Cl and Br in the mixture = 1.25 g

let the moles of Cl is a and the moles of Br = b ,then

33.5 xa + 79.9 x b = 1.25

now we have,

a + b = 0.0326 , multiplying it by 35.5 we get

35.5 x a + 35.5 x b = 1.16

substracting the above two equations we get

44.4 x b = 0.09

b = 0.002 mol

then, a = 0.0306 moles

moles of Br are = 0.002 so the moles of Na must also be 0.002 so the mass of NaBr will be =0.002 x 102.89 = 0.206 g of NaBr