Boron's atomic number is 5
Answer:
Option B. 176g/mol
Explanation:
We'll begin by writing the chemical formula for hexasodium difluoride. This is given below:
Hexasodium means 6 sodium atom
Difluoride means 2 fluorine atom.
Therefore, the formula for hexasodium difluoride is Na6F2.
The relative formula mass of a compound is obtained by simply adding the atomic masses of the elements present in the compound.
Thus, the relative formula mass of hexasodium difluoride, Na6F2 can be obtained as follow:
Molar mass of Na = 23g/mol
Molar mass of F = 19g/mol
Relative formula mass Na6F2 = (23x6) + (19x2)
= 138 + 38
= 176g/mol
Therefore, the relative formula mass of hexasodium difluoride, Na6F2 is 176g/mol
Answer:
The new pressure of the gas is 57.69atm
Explanation:
P1 = 50 atm
T1 = 390K
T2 = 450K
P2 = ?
This problem requires pressure law.
Pressure law states that the pressure of a fixed mass of gas is directly proportional to its temperature provided volume remains constant.
Mathematically,
P = kT, k = P / T
P1 / T1 = P2 / T2 = P3 / T3 .......Pn /Tn
P1 / T1 = P2 / T2
Solve for P2,
P2 = (P1 * T2) / T1
P2 = (50 * 450) / 390
P2 = 57.69atm
The new pressure of the gas is 57.69atm
Answer:
C.5
Explanation:
A number of electrons present in valence shell of penultimate Shell represents the group of elements.
For s block elements: no.of group=number of valence shell electron.
p block elements: no. of group= 2 + 10 + number of valence electrons.
d block elements: no. of group= number(n-1)d electrons + number of electrons in nth shell.
Here, the differential electron is in p orbital hence, it belongs to p block
No. of group= 2+ 10 + 3=15 i.e 15th group or VA group.