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3 years ago

Read the following, and answer the questions below. Remember to read the question carefully.

Chemistry

1 answer:

andreev551 [17]3 years ago

8 0

<h3>Question #1:</h3>

False.

Melting is a type of chemical change.

<h3>Question #2:</h3>

True.

If the substance's atoms change in any way, it is a chemical change.

<h3>Question #3:</h3>

True.

If a substance is broken or torn, it's still the same substance. (Take tearing paper, for example)

<h3>Question #4:</h3>

False.

Take boiling water for example, when you boil water, it is still water, right?

<h3>Question #5:</h3>

False.

<em><u>Every</u></em> chemical or physical change in matter includes change in energy. <u><em>Not most.</em></u>

<h3>Question #6</h3>

True.

Hydrogen peroxide (H2O2), has turned into water (H2O) and oxygen (O). The substance has change chemically, therefore it is an chemical change.

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I hoped this helps! If you have any questions, feel free to ask! ^^

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Write the balanced chemical equation for the following reaction. Phases are optional. Solid calcium chlorate decomposes to form

Tanya [424]

Answer:

Ca(ClO₃)₂ (s) → CaCl₂ (s) + 3O₂ (g)

Explanation:

1)<u> Word equation (given)</u>

<em>calcium chlorate (solid) → solid calcium chloride (solid) + oxygen (gas)</em>

2) <u>Chemical formulae of the reactant and products</u>:

<em><u>Calcium chlorate</u></em><em>: </em>

The most common oxidation states of chlorine are -1, +1, +3, +5, +7.

The suffix ate in chlorate means that chlorine atom is with the third lowest oxidation state (counting only the positive states). So, this is +5.

The oxidation state of calcium is +2.

Hence, the chemical formula of calcium chlorate is Ca(ClO₃)₂

<u><em>Calcium chloride</em></u>

The suffix ide in chloride means that chlorine is with oxidation state -1. Again the oxidation state of calcium is +2.

Hence, the chemical formula of calcium chloride is CaCl₂

<u><em>Oxygen</em></u>

Oxygen gas is a diatomic molecule, so its chemical formula is O₂.

<u><em>Phases</em></u>

The symbols s and g (in parenthesis) indicate the solid and gas phases respectively.

3) <u>Chemical equation</u>:

Ca(ClO₃)₂ (s) → CaCl₂ (s) + O₂ (g)

That equation is not balanced becasue the number of O atoms in the reactant side and in the product side are different.

4)<u> Balanced chemical equation:</u>

Add a 3 as coefficient in front of O₂(g), in the product side to balance:

Ca(ClO₃)₂ (s) → CaCl₂ (s) + 3O₂ (g)

Verify that all the atoms are balanced:

Atom Reactant side Product side

Ca 1 1

Cl 2 2

O 3×2 = 6 2×3 = 6

Conclusion: the equation is balanced and the final answer is:

Ca(ClO₃)₂ (s) → CaCl₂ (s) + 3O₂ (g)

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3 years ago

A standard solution of FeSCN2+ is prepared by combining 9.0 mL of 0.20 M Fe(NO3)3 with 1.0 mL of 0.0020 M KSCN . The standard so

Xelga [282]

Answer : The equilibrium concentration of $SCN^-$ in the trial solution is $4.58\times 10^{-8}M$

Explanation :

First we have to calculate the initial moles of $Fe^{3+}$ and $SCN^-$ .

$\text{Moles of }Fe^{3+}=\text{Concentration of }Fe^{3+}\times \text{Volume of solution}$

$\text{Moles of }Fe^{3+}=0.20M\times 9.0mL=1.8mmol$

and,

$\text{Moles of }SCN^-=\text{Concentration of }SCN^-\times \text{Volume of solution}$

$\text{Moles of }SCN^-=0.0020M\times 1.0mL=0.0020mmol$

The given balanced chemical reaction is,

$Fe^{3+}(aq)+SCN^-(aq)\rightleftharpoons FeSCN^{2+}(aq)$

Since 1 mole of $Fe^{3+}$ reacts with 1 mole of $SCN^-$ to give 1 mole of $FeSCN^{2+}$

The limiting reagent is, $SCN^-$

So, the number of moles of $FeSCN^{2+}$ = 0.0020 mmole

Now we have to calculate the concentration of $FeSCN^{2+}$ .

$\text{Concentration of }FeSCN^{2+}=\frac{0.0020mmol}{9.0mL+1.0mL}=0.00020M$

Using Beer-Lambert's law :

$A=\epsilon \times C\times l$

where,

A = absorbance of solution

C = concentration of solution

l = path length

$\epsilon$ = molar absorptivity coefficient

$\epsilon$ and l are same for stock solution and dilute solution. So,

$\epsilon l=\frac{A}{C}=\frac{0.480}{0.00020M}=2400M^{-1}$

For trial solution:

The equilibrium concentration of $SCN^-$ is,

$[SCN^-]_{eqm}=[SCN^-]_{initial}-[FeSCN^{2+}]$

$[SCN^-]_{initial}$ = 0.00050 M

Now calculate the $[FeSCN^{2+}]$ .

$C=\frac{A}{\epsilon l}=\frac{0.220}{2400M^{-1}}=9.17\times 10^{-5}M$

Now calculate the concentration of $SCN^-$ .

$[SCN^-]_{eqm}=[SCN^-]_{initial}-[FeSCN^{2+}]$

$[SCN^-]_{eqm}=(0.00050M)-(9.17\times 10^{-5}M)$

$[SCN^-]_{eqm}=4.58\times 10^{-8}M$

Therefore, the equilibrium concentration of $SCN^-$ in the trial solution is $4.58\times 10^{-8}M$

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lidiya [134]

Answer

Gymnastics

Explanation:

for the simple fact that they do cool stuff

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How might a cave an ant and a lake each meet the needs of an oranism

PIT_PIT [208]

The organism could live in the cave, eat the ant, and drink from the lake.

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