Answer:
The energy released from food was once energy from the sun that was captured by plants in the chemical process that forms plant matter (from air and water). Food provides animals with the materials they need for body repair and growth and the energy they need to maintain body warmth and for motion.
<u>Answer: </u>The correct statement is X is the effective nuclear charge, and it increases across a period.
<u>Explanation:</u>
We are given that:
X = number of protons − number of core electrons
Effective nuclear charge is defined as the actual nuclear charge (Z = number of protons) minus the screening effect caused by the electrons present between nucleus and valence electrons. These electrons are the core electrons.
The formula used for the calculation of effective nuclear charge given by Slater is:

where,
= effective nuclear charge
Z = atomic number or actual nuclear charge or number of protons
= Screening constant
The effective nuclear charge increases as we go from left to right in a period because nuclear charge increases with no effective increase in screening constant.
Hence, the correct answer is X is the effective nuclear charge, and it increases across a period.
The mass in grams of 8.94×10²² formula units of CuF₂ is 15.07 g
<h3>Avogadro's hypothesis </h3>
6.02×10²³ formula units = 1 mole of CuF₂
But
1 mole of CuF₂ = 101.5 g
Thus,
6.02×10²³ formula units = 101.5 g of CuF₂
<h3>How to determine the mass of 8.94×10²² formula units of CuF₂</h3>
6.02×10²³ formula units = 101.5 g of CuF₂
Therefore,
8.94×10²² formula units = (8.94×10²² × 101.5 ) / 6.02×10²³
8.94×10²² formula units = 15.07 g of CuF₂
Thus, 8.94×10²² formula units are present in 15.07 g of CuF₂
Learn more about Avogadro's number:
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Answer: (2)3.0 mol
Explanation: 222.3g= 222.3/74= 3.0 mol
1mol Ca(OH)2 is 74g
Fe (iron) has 26
protons,30 neutrons and 26 electrons. In order to calculate the binding energy,
first you need to find the total mass of all particles in the nucleus:
<span>
<span>26 x mass of proton + 30 x mass of neutron ( all in a.m.u.) =
say "m" </span></span>
<span>
Mass defect is m- 55.9207 amu, then convert it into grams and
put in equation E = mc2 to get binding energy of Fe.</span>
<span> Divide it by number of nucleons to get binding
energy per nucleon</span>.