I think it is "Known".
Radioactive decay is measured using a formula where the half-life <span>of an isotope is the time it takes for the original nuclei to decay half of its original amount.</span>

so:



so:

it means that
in

of acid there is

moles of acid

so:

it means that:
in

of water there is

moles of water
therefore:

So your answers are:

and the mole fraction is:
Answer:

Explanation:
Hello there!
In this case, according to the given STP (standard pressure and temperature), it is possible for us to realize that the equation to use here is the Avogadro's law as a directly proportional relationship between moles and volume:

In such a way, given the initial volume and both initial and final moles, we can easily compute the final volume as shown below:

Best regards!
Cu(s) + 2 AgNO3 = Cu(NO3)2 + 2 Ag 63.5 g Cu ---------------- 2 x 169.87 g AgNO3 ( mass Cu ?) -------------- 4.00 g AgNO3 mass Cu = 4.00 x 63.5 / 2 x 169.87 mass Cu = 254 / 339.74 = 0.747 g of Cu
Hope this helps