• To have equilibrium in a certain structure, the parameters x, y, z, w must satisfy the following equations. Find the values of x, y, z, w (problem from D.R.Green, J.Lewis - "Science with Pocket Calculators").

Rounding: x = 1.719·10^{−3}, y = 8.680·10^{−4}, z = 1.314·10^{−3},
w = 5.182·10^{−4}

• Find *x, y, z, w *integers such that
*x* Cu + *y* H_{2}SO_{4} → *z* CuSO_{4} + *w* H_{2}O + SO_{2}

Looking at the elements that appear on the two sides of the relationship, we have that it must be (for, in order, Cu, H, S, O):

Cu: x - z = 0 H: 2y - 2w = 0 S: y - z = 1 O: 4y - 4z - w = 2

Cu + 2H_{2}SO_{4} → CuSO_{4}+ 2H_{2}O + SO_{2}