(c) Cu + S → CuS is classified as a redox reaction
Explanation:
The following reactions are presented:
(a) K₂CrO₄ + BaCl₂ → BaCrO₄ + 2 KCl
(b) Pb²⁺ + 2 Br⁻ → PbBr₂
(c) Cu + S → CuS
Reaction (c) represents a redox reaction, as the oxidation states of the elements are changing. In this case:
Cu + S → CuS
In its elemental form, Cu has an oxidation state of 0, while in CuS (copper sulfide), its oxidation state changes to +2.
Similarly, S in its elemental form has an oxidation state of 0 and is -2 in CuS (copper sulfide).
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redox reactions
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<span>Quarks exist inside protons and neutrons but are not components of electrons.
Quarks are subatomic particles that possess mass and fractional (non-integer) electric charge.
Protons and neutrons are composed of quarks, whereas electrons are not, since electrons are considered energy carriers with charge rather than massive matter. Because quarks have mass, they cannot be part of electrons.</span>
We are tasked with determining the heat required to elevate the temperature of water from 85.0 ⁰F to 50.4 ⁰F.
To increase the temperature from 50.4 ⁰F to 85.0 ⁰F, a heat amount of 10.857 kJ is necessary.
The needed heat for the temperature increase can be calculated using the equation H = m×s×(t₂-t₁).
In this equation, H is the heat, s represents specific gravity at 4.184 J/g.⁰C, m is the mass of 135.0 g, t₁ (the initial temperature) is 50.4 ⁰F or 10.222 ⁰C, and t₂ (final temperature) stands at 85.0⁰F or 29.444 ⁰C.
After inputting these values, we find:
H = 135.0 g × 4.184 J/g.⁰C × (29.444 - 10.222) ⁰C
Simplifying gives us H = 10857.354 J or 10.857 kJ.
Thus, to elevate the temperature, 10857.354 J or 10.857 kJ of heat is necessary.
To determine the mass of salt using Avogadro's number, we find the moles of NaCl: 8.24x10²² molecules NaCl divided by 6.022x10²³ molecules NaCl per mole gives 0.14 mole NaCl. We can convert moles to grams of NaCl by multiplying 0.14 mole by 58g NaCl per mole, yielding a total of 8.12 g NaCl.
