V₁ = initial Volume of the balloon after it is blown up = 365 L
V₂ = new Volume of the balloon after it is taken outside = ?
T₁ = initial temperature of the balloon = 283 K
T₂ = new temperature of the balloon = 300 K
using the equation
V₁/V₂ = T₁/T₂
365/V₂ = 283/300
V₂ = 387 L
Given, half life of a certain radioactive element = 800 years.
Amount of substance remaining at time t = 12.5%
Lets consider the initial amount of the radioactive substance = 100%
Using the half life equation:
A = A₀(1/2)^t/t₁/₂
where A₀ is the amount of radioactive substance at time zero and A is the amount of radioactive substance at time t, and t₁/₂ is the half-life of the radioactive substance.
Plugging the given data into the half life equation we have,
12.5 = 100 . (1/2)^t/800
12.5/100 = (1/2)^t/800
0.125 = (0.5)^t/800
(0.5)^3 = (0.5)^t/800
3 = t/800
t = 2400 years
Thus the object is 2400 years old.
15. D is correct, exothermic reactions release heat
I am not sure about 16
Answer:
The law of conservation of mass states that in a closed system, mass is neither created nor destroyed during a chemical or physical reaction. The law of conservation of mass is applied whenever you balance a chemical equation.
Explanation:
According to the law of conservation of mass, the mass of the products in a chemical reaction must equal the mass of the reactants.
The law of conservation of mass is useful for a number of calculations and can be used to solve for unknown masses, such the amount of gas consumed or produced during a reaction.
It is applicable in a chemical when the the mass of the products in a chemical reaction is equal to the mass of the reactants.
But it is not applicable in a nuclear fusion as some of the mass is generated as energy.
<span>The first method to determine the chemical composition of a substance in space was using light. By determining red shift in the observed spectrum of light they could determine the elements they were observing. Different elements change the way light behaves and from this scientists can determine the makeup of things such as stars and nebulas.</span>
