Problem One
<em><u>Formula</u></em>
N(t) = No * (1/2)^[t/t_1/2]
<em><u>Givens</u></em>
N(t) = the current mass of the sample = 2.10 grams
No = The original mass of the sample = No [We're trying to find this].
t = time elapsed which is 2.6 billion years or 2.6 * 10^9 years.
t1/2 = the 1/2 life time which is 1.3 billion years of 1.3 *10^9
<em><u>Solution</u></em>
2.10 grams = No (1/2)^(2.6*10^9/1.3 * 10^9)
The 10^9s cancel and you are left with 2.6/1.3 = 2
2.10 grams = No (1/2)^2
2.10 grams = No (1/4) Multiply both sides by 4
2.10 * 4 = No (1/4)*4
8.4 grams = No
which is how many grams you originally had.
Answer B.
Problem Two

Solve for y
2 + 2 = y + 1
4 = y + 1
y = 3
Solve for z
1 + 1 = z + 0
z = 2
The 2 tells you that it is the second member on the periodic table. That's Helium. So the answer looks like this.

The mass of the Helium is 3 and its number is two.
All of the energy from the reactants will be lost to the surroundings.The energy found in the reactants remains in the system, and the reactants also take energy from the
surroundings is true of energy in reactants during endothermic reaction.
<h3>What is Endothermic reaction?</h3>
Endothermic reaction is a reaction in thermochemistry where the reactants absorb heat from the surrounding to form the products.
In an endothermic reaction, the products have more energy than the reactants, that is they absorbed more energy. The reactants have less energy,that is they loss energy . Therefore, the change in enthalpy is positive, heat is absorbed from the surroundings during the reaction.
Therefore, All of the energy from the reactants will be lost to the surroundings.
The energy found in the reactants remains in the system, and the reactants also take energy from the
surroundings is true of energy in reactants during endothermic reaction.
For more details on endothermic reaction check the link below.
brainly.com/question/6506846
Answer:
1. Ca(NO3)2 and AgCl3
2. AgCl3
3. Ca(NO3)2
4. a solid that forms out of a solution
Explanation:
1.
3CaCl2 + 2Ag(NO3)3 --> 3Ca(NO3)2 + 2AgCl3
idek what that is but i have the question on my homework rn