Answer:
A. 2
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A scientific theory is a well tested explanation of a natural phenomenon.
Answer:
2.5 g
Explanation:
Given data:
Masses of sample = 0.12 g, 1.8 g, 0.562 g
Combine mass of samples = ?
Solution:
When we add or subtract the values the number of significant figures after decimal in result must be equal to the given measurement having less number of decimal places.
0.12 g + 1.8 g + 0.562 g
2.482 g
In given three measurements 1.8 has less number of significant figure after decimal point which is only one digit. Thus the final value must contain one digit after decimal.
we will round of 2.482 g.
2.5 g
because the next digit after 4 is 8 that's why we will round 4 to 5.
Lead is a toxic metal that affects the central nervous system. A Pb-contaminated water sample contains 0.0011% Pb by mass. 13.6 × 10³ ml water contains 150 mg of Pb.
<h3>How to calculate the mass of solution ? </h3>
Given percentage of Pb present in the sample solution is 0.0011%
That means 0.0011 grams of Pb present in the 100g of solution.
So,
= 
= 13.6 × 10³ g water
<h3>What is Density ? </h3>
The mass per unit volume is called density. Density is represented as D or ρ.
It is expressed as:

where,
ρ = Density
m = mass of the object
V = Volume of object
Now put the value in above expression we get


V = 13.6 × 10³ ml
Thus from the above conclusion we can say that Lead is a toxic metal that affects the central nervous system. A Pb-contaminated water sample contains 0.0011% Pb by mass. 13.6 × 10³ ml water contains 150 mg of Pb.
Learn more about the Density here: brainly.com/question/1354972
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Answer:
Ea = 177x10³ J/mol
ko =
J/mol
Explanation:
The specific reaction rate can be calculated by Arrhenius equation:

Where k0 is a constant, Ea is the activation energy, R is the gas constant, and T the temperature in Kelvin.
k depends on the temperature, so, we can divide the k of two different temperatures:


Applying natural logathim in both sides of the equations:
ln(k1/k2) = Ea/RT2 - Ea/RT1
ln(k1/k2) = (Ea/R)x(1/T2 - 1/T1)
R = 8.314 J/mol.K
ln(2.46/47.5) = (Ea/8.314)x(1/528 - 1/492)
ln(0.052) = (Ea/8.314)x(-1.38x
-1.67x
xEa = -2.95
Ea = 177x10³ J/mol
To find ko, we just need to substitute Ea in one of the specific reaction rate equation:



ko =
J/mol