Answer: A index fossil is any animal or plant preserved in the rock record of the earth that is characteristic of a particular span of geologic time or environment. A useful index fossil must be distinctive or easily recognizable, abundant, and have a wide geographic distribution and a short range through time.
Explanation:
Answer:
The cubic centimeter of boron is 2.
Explanation:
Density:
Density is equal to the mass of substance divided by its volume.
Units:
SI unit of density is Kg/m3.
Other units are given below,
g/cm3, g/mL , kg/L
Formula:
D=m/v
D= density
m=mass
V=volume
Symbol:
The symbol used for density is called rho. It is represented by ρ. However letter D can also be used to represent the density.
Given data:
mass of boron = 4.68 g
density of boron = 2.34 g/cm³
volume = ? (cm³)
Solution:
d = m/ v
v = m/d
v = 4.68 g/ 2.34 g /cm³
v = 2 cm³
Answer:
pH = 12.08
Explanation:
First we <u>calculate how many moles of each substance were added</u>, using <em>the given volume and concentration</em>:
- HBr ⇒ 0.05 M * 75 mL = 3.75 mmol HBr
- KOH ⇒ 0.075 M * 74 mL = 5.55 mmol KOH
As HBr is a strong acid, it dissociates completely into H⁺ and Br⁻ species. Conversely, KOH dissociates completely into OH⁻ and K⁺ species.
As there are more OH⁻ moles than H⁺ moles (5.55 vs 3.75), we <u>calculate how many OH⁻ moles remain after the reaction</u>:
- 5.55 - 3.75 = 1.8 mmoles OH⁻
With that<em> number of moles and the volume of the mixture</em>, we <u>calculate [OH⁻]</u>:
- [OH⁻] = 1.8 mmol / (75 mL + 74 mL) = 0.0121 M
With [OH⁻], we <u>calculate the pOH</u>:
With the pOH, we <u>calculate the pH</u>:
Answer:
The correct answer is "D. The difference in their electronegativities is greater than 1.7"
Explanation:
An ionic bond is produced between metallic and non-metallic atoms, where electrons are completely transferred from one atom to another. During this process, one atom loses electrons and another one gains them, forming ions. Usually, the metal gives up its electrons forming a cation to the nonmetal element, which forms an anion.
So, this type of bond consists of the attraction of atoms with electric charges of different signs, that is, the bond is established when atoms of low electronegative elements (metals) are bonded with atoms of highly electronegative elements (nonmetals).
So you can say that atoms of electronegativity difference equal to or greater than 1.7 participate in this type of bond (with its exceptions).
<u><em>The correct answer is "D. The difference in their electronegativities is greater than 1.7"</em></u>
Perspex and polythene are good examples of insulators.
