Answer:
A. there is an isotope of lanthanum with an atomic mass of 138.9
Explanation:
By knowing the different atomic masses of both Lanthanum atoms, we can not tell anything about their occurence in nature. Therefore, all the last three options are incorrect. Because, the atomic mass does not tell anything about the availability or natural abundance of an element.
Now, the isotopes of an element are those elements, which have same number of electrons and protons as the original element, but different number of neutrons. Therefore, they have same atomic number but, different atomic weight or atomic masses.
Hence, by looking at an elements having same atomic number, but different atomic masses, we can identify them as isotopes.
Thus, the correct option is:
<u>A. there is an isotope of lanthanum with an atomic mass of 138.9.</u>
Use the ideal gas formula-----> PV= nRT
P= 2.50 atm
V= 250 mL= 0.250 L
n= 0.100 moles
R= 0.0821 atmxL/molesxK
T= ?
T= PV/nR
T= (2.50 atm x 0.250 L) / (0.100 moles x 0.0821)= 76.1 K
Answer:
i need a picture or more info to understand
<h3>
Answer:</h3>
2.83 g/cm³
<h3>
Explanation:</h3>
- Density of a substance is the ratio of mass of the substance to its volume.
Therefore;
- Density is given by dividing mass of a substance by its volume.
- It is measure in g/cubic centimeters or kg per cubic meters.
In this case;
Density of Al = 2830 Kg/m³
We are required to convert is to g/cm³
We use the relationship;
1 g/cm³ = 1000 kg/m³
Therefore;
= 2830 kg/m³ ÷ 1000 kg/m³
= 2.83 g/cm³
Hence, 2830 kg/m³ of Aluminium is equivalent to 2.83 g/cm³
