One half-life: 5 grams
Two half-lives: 2.5 grams
Answer:
The specific heat of iron is 0.45 J/g.°C
Explanation:
The amount of heat absorbed by the metal is given by:
heat = m x Sh x ΔT
From the data, we have:
heat = 180.8 J
mass = m = 22.44 g
ΔT = Final temperature - Initial temperature = 39.0°C - 21.1 °C = 17.9°C
Thus, we calculate the specific heat of iron (Sh) as follows:
Sh = heat/(m x ΔT) = (180.8 J)/(22.44 g x 17.9°C) = 0.45 J/g.°C
One thing to notice in the question is, we are asked about molecular oxygen that has formula O2 not atomic oxygen O.
As we are asked about molecular oxygen, we will answer the question in terms of number of molecules that are present in 16 grams of molecular oxygen.
To get the number of molecules present in 16 grams of O2, we will use the formula:
No. of molecules = no. of moles x Avogadro's number (NA)----- eq 1)
As we know:
The number of moles = mass/ molar mass of molecule
Here we have been given mass already, 16 grams and the molar mass of O2 is 32 grams.
Putting the values in above formula:
= 16/32
= 0.5 moles
Putting the number of moles and Avogadro's number (6.02 * 10^23) in eq 1
No. of molecules = 0.5 x 6.02 * 10^23
=3.01 x 10^23 molecules
or 301,000,000,000,000,000,000,000 molecules
This means that 16 grams of 3.01 x 10^23 molecules of oxygen.
Hope it helps!
Answer:
The 197Au isotope has 79 protons, 79 electrons and 118 neutrons
Explanation:
Step 1: The isotope = 197Au
Step 2: Calculate neutrons, electrons and protons
197 = Number of protons + number of neutrons
Isotopes always have the same proton number ( is the same as the atomic number). For Gold (Au) is this 79.
The number of electrons is equal to the number of protons in a neutral atom. Since we have 79 protons, there are also 79 electrons.
All isotopes of Au have a different number of neutrons.
The number of neutrons = 197 -79 = 118 neutrons
The 197Au isotope has 79 protons, 79 electrons and 118 neutrons
