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3 years ago

13

Magnesium burns with a very bright light. When the flame goes out, a White powder is left behind. What is the name of that white

powder?

2 answers:

oksano4ka [1.4K]3 years ago

8 0

The white power is formed from the combustion of magnesium with oxygen. Therefore, the white powder remaining is MgO.

gavmur [86]3 years ago

6 0

The white powder is called Magnesium oxide. Or it's chemical symbol MgO

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3 years ago

Calculate the solubility of CaF2 in g/L (Ksp = 4.0 x 10-8). 2. What is the pH of a solution containing a hydrogen ion concentrat

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Answer:

$\large \boxed{1. \text{ 0.17 g/L; 2. 3.52; 3. Cl; 4. (a) +3; (b) +4; (c) +6}}$

Explanation:

1. Solubility of CaF_2

(a) Molar solubility

CaF₂ ⇌ Ca²⁺ + 2F⁻

$K_{\text{sp }} = \text{[Ca$^{2+}$]}\text{[F$^{-}$]}^{2}= 4.0 \times 10^{-8}\\s(2s)^{2}=4.0 \times 10^{-8}\\4s^{3} = 4.0 \times 10^{-8}\\s^{3} = 1.0 \times 10^{-8}\\s =2.2 \times 10^{-3}\text{ mol/L}$

(b) Mass solubility

$\text{Solubility} = 2.2 \times 10^{-3} \text{ mol/L} \times \dfrac{\text{78.07 g}}{\text{1 L }} = \text{0.17 g/L}\\\\\text{The solubility of CaF$_{2}$ is $\large \boxed{\textbf{0.17 g/L}}$}$

2. pH

pH = -log [H⁺] = -log(3.0 × 10⁻⁴) = 3.52

3. Oxidizing and reducing agents

Zn + Cl₂ ⟶ ZnCl₂

$\rm \stackrel{\hbox{0}}{\hbox{Zn}} + \stackrel{\hbox{0}}{\hbox{ Cl}_{2} }\longrightarrow \stackrel{\hbox{+2}}{\hbox{Zn}}\stackrel{\hbox{-1}}{\hbox{Cl}_{2}}$

The oxidation number of Cl has decreased from 0 to -1.

Cl has been reduced, so Cl is the oxidizing agent.

4. Oxidation numbers

(a) Al₂O₃

$\stackrel{\hbox{$\mathbf{+3}$}}{\hbox{Al}_{2}}\stackrel{\hbox{-2}}{\hbox{O}_{3}}$

1O = -2; 3O = -6; 2Al = +6; 1Al = +3

(b) XeF₄

$\stackrel{\hbox{$\mathbf{+4}$}}{\hbox{Xe}}\stackrel{\hbox{-1}}{\hbox{F}_{4}}$

1F = -1; 4F = -4; 1 Xe = +4

(c) K₂Cr₂O₇

$\stackrel{\hbox{${+1}$}}{\hbox{K}_{2}}\stackrel{\hbox{$\mathbf{+6}$}}{\hbox{Cr}_{2}}\stackrel{\hbox{-2}}{\hbox{O}_{7}}$

1K = +1; 2K = +2; 1O = -2; 7O = -14

+2 - 14 = -12

2Cr = + 12; 1 Cr = +6

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3 years ago

A chemist observes that a large molecule reacts as if it were much smaller. The chemist proposes that the molecule is folded in

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Answer:

Hypothesis

Explanation:

The following steps are applicable when we wish to prove a specific fact:

a hypothesis is made; this is a statement that we provide after some observations and we wish to either prove or deny it;
multiple experiments are carried out in order to gather significantly substantial amount of data that can be then further analyzed and any tendencies can be noticed;
based on the data gathered, conclusions are made: we either prove or deny the hypothesis. If hypothesis is proved, it may become a theory over long time.

In the context of this problem, we're at the first step where we make a hypothesis.

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Answer: Chemical composition modification (or, physical signal would be color).

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3 years ago

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