Answer:
-154KJ/mol
Explanation:
mole of 100ml sample of 0.2M aqueous HCl = Molarity × volume in Liter
= 0.2 × 100 / 1000 ( 1L = 1000 ml) = 0.02 mol and 0.02 mole of HCl solution require 0.02 mole of ammonia according to the mole ratio in the balanced equation.
Heat loss by the reaction = heat gain by calorimeter = mcΔT + 480 J/K
where m is the mass of water = 100g + 100g = 200g since mass of 100ml of water = 100g and it is in both of them and specific heat capacity of water 4.184 J/gK
heat gain by calorimeter = (4.184 × 200 + 480) × 2.34 = 3081.3 J
ΔH per mole = heat loss / number of mole = 3081.3 / 0.02 = 154065.6 = -154KJ/mol
For this problem, we use the formula for sensible heat which is written below:
Q= mCpΔT
where Q is the energy
Cp is the specific heat capacity
ΔT is the temperature difference
Q = (55.5 g)(<span>0.214 cal/g</span>·°C)(48.6°C- 23°C)
<em>Q = 304.05 cal</em>
1.Hans and Zacharias Janssen created the first microscope.
2.Robert Hooke was the first to use the word “cell.”
3.Anton van Leeuwenhoek observed small organisms he called “animalcules.”
4.Matthias Schleiden theorized that plants are made of cells.
5.Theodor Schwann theorized that animals are made of cells.
6.Rudolf Virchow theorized that cells come from other pre-existing cells.
Answer:
Explanation:
The changes in properties from metals to non-metals on a periodic table can be measured and determined by the metallicity or electropositivity of elements.
Metallicity is a measure of the tendency of atoms of an element to lose electrons.
a.
Down a periodic group, metallicity increases.
b.
Across a period from left to right electropositivity or metallicity decreases.
Metals are found in the left part of periodic table and the most reactive metal sits in the lower left corner. Non-metals are towards the right side of the table.
N₀ is the number of C-14 atoms per kg of carbon in the original sample at time = Os when its carbon was of the same kind as that present in the atmosphere today. After time ts, due to radioactive decay, the number of C-14 atoms per kg of carbon is the same sample which has decreased to N. λ is the radioactive decay constant.
Therefore N = N₀e-λt which is the radioactive decay equation,
N₀/N = eλt In (N₀.N= λt. This is the equation 1
The mass of carbon which is present in the sample os mc kg. So the sample has a radioactivity of A/mc decay is/kg. r is the mass of C-14 in original sample at t= 0 per total mass of carbon in a sample which is equal to [(total number of C-14 atoms in the sample at t m=m 0) × ma]/ total mass of carbon in the sample.
Now that the total number of C-14 atoms in the sample at t= 0/ total mass of carbon in sample = N₀ then r = N₀×ma
So N₀ = r/ma. this equation 2.
The activity of the radioactive substance is directly proportional to the number of atoms present at the time.
Activity = A number of decays/ sec = dN/dt = λ(number of atoms of C-14 present at time t) =
λ₁(N×mc). By rearranging we get N = A/(λmc) this is equation 3.
By plugging in equation 2 and 3 and solve t to get
t = 1/λ In (rλmc/m₀A).
