When it is summer in the Northern Hemisphere, it is winter in the Southern Hemisphere. It could be A I’m not sure if this helps.
Since, the options have not been given the question is incomplete.
What is Darwin's name for species that do not appear to have changed for millions of years?
a.
Dinosaurs
b.
Living fossils
c.
Old souls
d.
Ancient moderns
Answer: b. Living fossil
Explanation:
In 1859 Charles Darwin proposed the term living fossil, that means a species or group of species that had not changed in terms of evolutionary context thus can be useful in tracing the extinct or previously existing forms of life. The examples of the living fossils are horseshoe crabs, ginkgo (Conifers) and tuatara. These group of animals were existed unchanged in the Ordovician, Permian, and Triassic periods respectively with few surviving species.
molar mass of PF5 = 125.966 g/mol
125 g PF5 × (1 mol PF5/125.966 g PF5) = 0.992 mol PF5
0.992 mol PF5 × (6.022 × 10^23 molecules PF5);
= 5.97 × 10^23 molecules PF5
Since there 5 fluorine atoms per molecule of PF5,
(5.97.× 10^23 molecules PF5) × (5 atoms F/1 molecule PF5)
= 2.99 × 10^24 atoms F
For the whole set of problems, always remember the Avogadro’s
number is 6.023*10^23 units per mole of a substance. Units could be atoms,
molecules or formula units.
The first question asks for the number of molecules of NaNO3.
The molar mass of NaNO3 is 85 grams per mole. So,
<span>150g NaNO3(1mole NaNO3/85 grams NaNO3)(6.023*10^23
molecules/1mole NaNO3)=1.063*10^24 molecules of NaNO3</span>
<span>5.7*10^46 molecules of NaNO3(1mole NaNO3/6.023*10^23
molecules)(85 grams NaNO3/1mole NaNO3) = 8.044*10^24 grams NaNO3</span>
For the molar mass of water, we have 18.02grams per mole.
301 moles H2O(18.02 grams H2O/1
mole H2O) = 5424.02 grams H2O
For the molar mass of sulfuric
acid, we have 98.08 grams per mole.
25g H2SO4(I mole H2SO4/98.08g H2SO4) =
0.2549 mole H2SO4
For the molar mass of Ca(OH)2,
we have 74.1 grams per mole.
252gCa(OH)2(1mol/74.1g)(6.023*10^23/1mol)
= 2.048*10^24 molecules of Ca(OH)2
For the molar mass of calcium,
we have 40 grams of Ca per mole.
6.7*10^35 atoms Ca(1 mole
Ca/6.023*10^23 atoms)(40g Ca/1mol Ca) = <span>4.45*10^13 grams Ca</span>
