Option no. 2 subtracting the atomic number from the mass number
Example: Zn - 65 atomic weight or mass/mass number
30 atomic number
65-30 = 35 number of neutrons
Rare earth metals are a group of 17 elements - lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium, yttrium - that appear in low concentrations in the ground
1 CH4 (g) + 2 O2 (g) -----> CO2 (g) + 2H2O(l) ΔH= - 890 kJ
1 mol 2 mol
1) If ΔH has minus, it means "release". We need only "release" choices.<span>
2) From reaction
1 mol </span>CH4 (g) "releases" ΔH= - 890 kJ - We do not have this choice.
2 mol O2 (g) "release" ΔH= - 890 kJ, so
1 mol O2 (g) "release" ΔH= - 445 kJ
Correct answer is B.
Answer:
True.
Explanation:
Btw ya spelled mitosis wrong...
Answer:
H-O-H polar
O-C-O nonpolar
H-C-N polar
Explanation:
Looking up the electronegativities of the atoms involved in this question, we have:
Atom Electronegativity
H 2.2
C 2.55
N 3.04
O 3.44
All of the atoms differ in electronegativity resulting in individual dipole moments in H-O, O-C, H-C and C-N bonds. To find if the molecules will be polar we need to consider the structure of the compound to see if there is a resultant dipole moment.
In H-O-H, we have 2 lone pairs of electrons around the central oxygen atom which push the angle H-O-H of the ideal tetrahedral structure to be smaller than 109.5 º resulting in an overall dipole moment making it polar.
In O-C-O, we have two dipole moments that exactly cancel each other in the linear molecule since the central carbon atom does not have lone pairs of electrons since it has 2 double bonds. Therefore the molecule is nonpolar.
In H-C-N, again we have have a central carbon atom without lone pairs of electrons and the shape of the molecule is linear. But, now we have that the dipole moment in C-N is stronger than the H-C dipole because of the difference in electronegativity of nitrogen compared to hydrogen. The molecule has an overall dipole moment and it is polar.
