Answer:
6.73g
Explanation:
T½ = 5.2days
No = 80g
N = ?
T = 20.8days
We'll have to find the disintegration constant first so that we can plug it into the equation that will help us find the mass of the sample after 20.8 days
T½ = In2 / λ
T½ = half life
λ = disintegration constant
λ = In2 / T½
λ = 0.693 / 5.8
λ = 0.119
In(N / No) = -λt
N = final mass of the radioactive sample
No = initial mass of the sample
λ = disintegration constant
t = time for the radioactive decay
In(N/No) = -λt
N / No = e^-λt
N = No(e^-λt)
N = 80 × e^-(0.119 × 20.8)
N = 80 × e^-2.4752
N = 80 × 0.0841
N = 6.728g
The mass of the sample after 20.8 days is approximately 6.73g
Answer:
Percent by mass of water is 56%
Explanation:
First of all calculate the mass of hydrated compound as,
Mass of Sodium = Na × 2 = 22.99 × 1 = 45.98 g
Mass of Sulfur = S × 1 = 32.06 × 1 = 32.06 g
Mass of Oxygen = O × 14 = 16 × 14 = 224 g
Mass of Hydrogen = H × 20 = 1.01 × 20 = 20.2 g
Mass of Na₂S0₄.10H₂O = 322.24 g
Secondly, calculate mass of water present in hydrated compound. For this one should look for the coefficient present before H₂O in molecular formula of hydrated compound. In this case the coefficient is 10, so the mass of water is...
Mass of water = 10 × 18.02
Mass of water = 180.2 g
Now, we will apply following formula to find percent of water in hydrated compound,
%H₂O = Mass of H₂O / Mass of Hydrated Compound × 100
Putting values,
%H₂O = 180.2 g / 322.24 g × 100
%H₂O = 55.92 % ≈ 56%
It is clearly (a) is Einstein's equation
Answer;
1.6 kg.
Solution;
The density is 1.36 g/ml;
The volume is 1.25 qt
However; 1 qt = 946.35 ml
Mass is given by; density × volume;
= 1.25 qts × 946.25 ml/qt × 1.36 g/ml =1609 g
but; 1 kg = 1000 g
Hence the mass = 1609/1000 = 1.609 Kg or 1.61 (sig figs)
An introduced species could be invasive if it can outcompete native species for resources. Examples are light, nutrients, water, food etc.
