Consider the following species when answering the following question: (i) NF3
Of the molecules below, only ________ is nonpolar.
Only BF₃ is non polar.
The non polar molecule is one which will have zero dipole moment.
This zero dipole moment is possble if
a) the bonds are non polar (completely) and there is no lone electrons
b) the bonds are polar but the overall dipole moment cancel each other due to planar geometry of molecule
i) BF₃ : This is trigonal planar molecule. The overall dipole moment is zero due to symmetric distribution of electrons and thus dipole cancel each other.
ii) NF₃ : there is lone pair of electron and the bonds are polar.
iii) PBr₃: Again presence of lone pair of electrons and thus ssymmetric distribution of electrons
iv) BrCl₃ : The bonds are polar and molecule is not planar.
v) IF₃ : bonds are polar.
A fossil is found to have a 14 C 14C level of 70.0 70.0 % compared to living organisms. How old is the fossil?
The age of the fossil be .
Formula used :
= initial mass of isotope C-14 = x
N = mass of the parent isotope left after the time, (t) = 70.0% of x=0.07x
= half life of the isotope C-14 = 5730 years
= rate constant
Let the age of the fossil be t.
Now put all the given values in this formula, we get t :
The age of the fossil be .
549.8 expressed in standard form is
The standard form of a number can be expressed in term of exponent of 10. The standard form of 549.8 is 5.49 × 10².What is scientific notation?
Scientific notation of a number means to express values that are either too big or too little to be conveniently stated in decimal form (typically would result in a long string of digits).
It is also known as standard form in the UK and scientific form, standard index form, and standard form. Scientists, mathematicians, and engineers frequently utilize this base ten notation because it can make some mathematical operations simpler.
It is typically referred to as "SCI" display mode on scientific calculators. In the decimal system non-zero values are written in the form in scientific notation as:
m ×10ⁿ, or m times ten multiplied by n, where n is an integer.
Similarly the decimal place of 549.8 can be placed to two as written by 5.498 × 10² , thus multiplying with 100 make the original value 549.8.
To find more on scientific notation, refer here:
3.15 g of an unknown gas at 35 °C and 1.10 atm is stored in a 1.85-L flask. What is the density of the gas? what is the molar mass of the gas?
In this case, one uses the ideal gas equation:
By solving for moles in terms of mass and molar mass one obtains:
On the other hand, the density is easily computed as shown below: