Answer:
1.806 × 10²⁴ atoms
Explanation:
To obtain the number of atoms a substance contain, we have to multiply the number of moles in that substance (n) by Avogadro's number, which is 6.02 × 10²³.
According to this question, a sample of carbon tetrachloride (CCl4) contains 3 moles of the substance. The number of atoms in CCl4 is calculated thus:
number of atoms = 3 × 6.02 × 10²³
number of atoms = 18.06 × 10²³
number of atoms = 1.806 × 10²⁴ atoms.
Unfortunately, we have not fully solved the 'nitrogen problem'. To do this, we must halve the amount of nitrogen we dump into the environment by mid-century or our ecosystems will face epidemics of toxic tides, lifeless rivers, and dead oceans. And that to do that will require, among other things, almost doubling the efficiency of nitrogen use on the world’s farms.
False
Although we use many of their ideas to describe atoms today, such as the existence of a tiny, dense nucleus in an atom (proposed by Rutherford), or the notion that all atoms of an element are identical (proposed by Dalton), some of their ideas have been rejected by the modern theory of the atom.
For example, Thompson came up with the plum pudding model to describe an atom, which resembled a sphere of positive charge with electrons embedded in it. We know now, however, that atoms are mostly empty space with a tiny, dense nucleus.
Another example is Dalton's atomic theory, which stated that atoms are indivisible particles. However, this was disproved by the discovery of subatomic particles.
Answer:
C. The reaction can be broken down and performed in steps
Explanation:
Hess's Law of Constant Heat Summation states that irrespective of the number of steps followed in a reaction, the total enthalpy change for the reaction is the sum of all enthalpy changes corresponding to all the steps in the overall reaction. The implication of this law is that the change of enthalpy in a chemical reaction is independent of the pathway between the initial and final states of the system.
To obtain MgO safely without exposing magnesium to flame, the reaction sequence shown in the image attached may be carried out. Since the enthalpy of the overall reaction is independent of the pathway between the initial and final states of the system, the sum of the enthalpy of each step yields the enthalpy of formation of MgO.
Although 1013.25 mb (760 mm Hg) is considered to be the standard atmospheric pressure at sea level, it does not mean that the pressure at this level has this value, actually this being 1011 mb.
