Hi there! Air and sunlight can definitely be reused. Those are abundant and renewable resources. Therefore, A and D are eliminated. There is a limited amount of water, however, it's impossible to run out of it to the point that there's no more on Earth. C is out. The only answer choice that makes sense is coal, because it's a nonrenewable resource, and it takes millions of years to make more of. It's a fossil fuel, so once we use them up, we can't get anymore during our lives. The answer is B: coal.
Answer:
Mg
Explanation:
The standard reduction potentials are
<u>E°/V
</u>
Au³⁺(aq ) + 3e⁻ ⟶ Au(s); 1.42
Hg²⁺(aq) + 2e⁻ ⟶ Hg(l); 0.85
Ag⁺(aq) + e⁻ ⟶ Ag(s); 0.80
Cu²⁺(aq) + 2e⁻ ⟶ Cu(s); 0.34
Mg2+(aq) + 2e- ⟶ Mg(s); -2.38
The more negative the standard reduction potential, the stronger the metal is as a reducing agent.
Mg is the only metal with a standard reduction potential lower than that of Cu, so
Only Mg will react spontaneously with Cu²⁺.
E=mc (square) E= mass times capacity squared
<u>Given</u> :
- Amount = 20 kg
- Heat energy absorbed = 237,000 J
- Temperature change = 15 °C
<u>Formula applied</u> :
- Q = absorbed heat
- m = mass
- c = specific heat capacity
- ΔT = temperature change
Let's solve for c !
⇒ 237,000 = 20 × c × 15
⇒ c = 237,000 ÷ 300
⇒ 
∴ The specific heat capacity of granite is <u>790 J kg⁻¹ K⁻¹</u>.
The characteristic bright-line spectrum of an element is produced when its electrons return to lower energy levels To be in the ground state all electrons must be in their lowest energy state; all excited atoms must lose energy. The lost energy appears in the form of light. Hope this helped :)
