Question

A mixture of {\rm NaCl} and {\rm NaBr} has a mass of 2.10{\rm g} and is found to contain 0.71{\rm g} of {\rm Na} What is the mass of {\rm NaBr} in the mixture?

Answer 1

Let X = mass NaCl and
let Y = mass NaBr
two equation in two unknowns.
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X + Y = 2.10g
X(atomic mass Na/molar mass NaCl) + Y(atomic mass Na/molar mass NaBr) = 0.71g

Solve for X and Y.