PLEASE HELP!! Mole Practice 1. How many moles of HCl are in 7.80 X 10^22 molecules?
___0.13 moles of HCI_

2. How many atoms are in 5.6 moles of Na?
3.2 E 24 atoms of Na

3. A chemical reaction produces 3.81g potassium chloride (KCI). How many formula units of
potassium chloride are there?*Find molar mass of KCI
Answer_3.08 E 22 formula units of KCI

4. Calculate the molar mass of Fe2(SO2)3. Then calculate the mass of iron(III) sulfate of 4.05X1023
formula units.
_269g Fe2(SO4)3_

5. Determine the number of liters in 4.32 grams of water (H2O)
__ 5.37LH2O___

electron microscopy and scanning tunneling microscopes gives us a greater understanding of atoms by being able to see the atom itself, and lets us see some atomic reactions.

explanation:

part 1: the half-life of the element is 22 years.

part 2: it will take 132.02 year for the sample to decay from 308.0 g to 4.8125 g.

explanation:

part 1: there are two ways to determine the half life time.

first way: the half life time can be determined directly from its definition as it is the time required for the sample to decay to its half concentration.

from the data the initial concentration was 45.0 g and decayed to its half value (22.5 g) in 22.0 years.

second way: the radio active decay is considered first order reaction so we can use the laws of first order reactions.

k = (1/t) ln (a/a-x), where k is the rate constant of the reaction,

t is the time of the reaction

a is the initial concentration of the reactant

a-x is the remaining concentration at time (t)

a = 45.0 g the initial concentration at t = 0 year.

at t = 22 year, a-x = 22.5 g

then k = (1/22 year) ln (45.0 g/ 22.5 g) = 0.0315 year-1.

the half-life time (t1/2) = ln 2/ k = 0.693/ k =0.693/ 0.0315 = 22 years.

part 2:

using the same law k = (1/t) ln (a/a-x),

using the given data; a = 308.0 g and a-x = 4.8125 g and the calculated k from the part 1 (k = 0.0315 year-1)

t = (1/k) ln (a/a-x) = (1/0.0315) ln (308.0/ 4.8125) = 132.02 years

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