The answer is 0.62g.
Solution:
From year 1960 to year 2030, it has been
2030-1960 = 70 years
The half-life of the radioactive element is 28 years, then the sample will go through
70 years * (1 half-life/28 years) = 2.5 half-lives
Starting with a 3.5 gram sample, we will have
3.5*(1/2) after one half-life passes
3.5*(1/2) * (1/2) = 3.5*(1/4) after two half-lives pass
3.5*(1/4) * (1/2) = 3.5*(1/8) after three half-lives pass and so on
Therefore, we can write the remaining amount of the sample after the number n of half-lives have passed as
mass of sample = initial mass of sample/2^n
The mass of the remaining sample for n = 2.5half-lives can be now calculated as
mass of sample = 3.5 grams / 2^2.5 = 0.62 g
Answer:
its a strong nuclear force
Answer:
Explanation:
1. A measure of how quickly velocity is changing is the acceleration
Acceleration is the rate of change of velocity with time. The rate at which a body is changing its velocity is known as the acceleration.
It is measured in the unit m/s²
2. Speed in a given direction is the velocity
Velocity is a vector quantity which measures the magnitude of motion in a specific direction. It is simply speed in a given direction.
When we say a motorcycle travels at the rate of 5m/s due east, we are describing the velocity of such body.
3. Force that resists moving one object against another is the friction
Friction is a force that opposes motion. It prevents a body from moving.
4. Measure of the pull of gravity on an object Weight
Weight is a measure of the amount of gravitational force on a body. It is mathematically expressed as;
W = mg
W is the weight, m is the mass and g is the acceleration due to gravity
5 Tendency of an object to resist a change in motion is inertia
Inertia is the tendency of body to resist change in motion. It is the ability of a body to remain in a perpetual state of rest.
6 Size is the magnitude
Basically, the arrangement of electrons in electronic configuration follows three principles:
1. Aufbau Principle
You start from the highest energy level to the lowest. The arrangement is: <span>1s<2s<2p<3s<3p<4s<3d<4p<5s<4d<5p<6s<4f<5d<6p<7s<5f<6d<7p.
2. Hund's Rule
Each box in the configuration can hold up to 2 electrons. This rule tells you to fill all boxes of one particular subshell with 1 electron first, before double occupying them.
3. Pauli's Exclusion Principle
This rule tells you that the two electrons in a box shall always have opposite spins, represented by one half-arrow up and one half-arrow down.</span>
Best Answer: <span>(a)
8.9 x 10^-7 = x^2 / 0.15-x
x = [OH-] = 0.00037 M
pOH = 3.4
pH = 14 - 3.4 = 10.6
(b)
Ka = Kw/Kb = 5.6 x 10^-10 = x^2 / 0.20-x
x = [H+] = 0.000011 M
pH = 5.0</span>
