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4 years ago

Help please ASAP 10 point

Chemistry

1 answer:

charle [14.2K]4 years ago

5 0

6a. physical reaction
6b. endothermic reaction
7a. physical reaction
7b. the reactants are carbon dioxide, water and light energy. the product is starch
7c. exothermic reaction

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1. Which is not an example of a physical change to a wooden stick?

Anvisha [2.4K]

The answer is C. burning the stick. This is because burning the stick will change the chemical properties of the wood, and it will not be wood anymore, it will be ash and the rest will be heart or gas.

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3 years ago

Describe the changed that happened in the crayon and candle when they cooled after 3 to 5 minutes.

AleksandrR [38]

Answer:

The change was physical, meaning it went from liquid to solid, or the other way around.

Explanation:

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3 years ago

The molar mass of KCl is 74. 55 g/mol. If 8. 45 g KCl are dissolved in 0. 750 L of solution, what is the molarity of the solutio

rosijanka [135]

Molarity is the strength of the solution or the ratio of the moles and the volume of the solution. The molarity of the solution is 0.1516 mol per Liter.

<h3>What is molarity?</h3>

Molarity is the molar concentration of the solution that tells about the amount of the solute or the substance dissolved in the given amount of the solution.

Given,

Mass of potassium chloride = 8.45 g
Molar mass of potassium chloride = 74. 55 g/mol
Volume of the solution = 0.750 L

Moles can be calculated by:

$\begin{aligned}\rm Moles &= \rm \dfrac{Mass }{\rm Molar \;mass}\\\\&= \dfrac{8.45}{74.55}\\\\&= 0.1133\;\rm mol\end{aligned}$

Calculate molarity by:

$\rm Molarity = \dfrac{moles}{\text{Volume in L}}$

Substituting values in the equation:

$\begin{aligned}\rm Molarity &= \dfrac{0.1133}{0.750}\\\\&= 0.1516 \;\rm mol\;L^{-1}\end{aligned}$

Therefore, the molarity of the solution is 0.1516 mol per Liter.

Learn more about molarity here:

brainly.com/question/2560307

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2 years ago

A 35.0-mL solution of 0.075 M CaCl2 is mixed with 25.0 mL of 0.090 M BaCl2.

Korolek [52]

Answer:

The fluoride which precipitates first is CaF₂

Explanation:

When F⁻ is added, CaF₂ and BaF₂ are produced following the ksp equation:

For CaF₂:

Ksp = 3.2x10⁻¹¹ = [Ca²⁺] [F⁻]²

<em>Where [Ca²⁺] = 0.075M * {35mL / (25mL + 35mL)} = 0.04375M</em>

3.2x10⁻¹¹ = [0.04375M] [F⁻]²

[F⁻]² = 7.31x10⁻¹⁰

[F⁻] = 2.7x10⁻⁵M

<h3>CaF₂ begins precipitation when [F⁻] = 2.7x10⁻⁵M.</h3>

For BaF₂:

Ksp = 1.5x10⁻⁶ = [Ba²⁺] [F⁻]²

<em>Where [Ba²⁺] = 0.090M * {25mL / (25mL + 35mL)} = 0.0375M</em>

1.5x10⁻⁶ = [0.0375M] [F⁻]²

[F⁻]² = 4x10⁻⁵

[F⁻] = 6.3x10⁻³M

BaF₂ begins precipitation when [F⁻] = 6.3x10⁻³M

Thus, the fluoride which precipitates first is CaF₂

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3 years ago

Which of the following is a correct lewis structure for sulfur dioxide, so2?

pshichka [43]

The correct Lewis structure of SO2 is the Lewis structure that shows all the 12 valence electrons in the molecule.

A Lewis structure shows the number of valence electrons on the valence shell of all the atoms in a compound. The electrons are shown as dots around the symbol of each element or a dash to indicate shared electrons in a covalent bond.

Looking at the Lewis structure of SO2 attached to this answer, we can see the twelve valence electrons in the molecule and how they are distributed around each atom as shown.

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2 years ago