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3 years ago

When two substances are mixed and light is produced is it a chemical or physical change?

Chemistry

2 answers:

ziro4ka [17]3 years ago

8 0

Chemical because its mixing two chemicals which are substances

ASHA 777 [7]3 years ago

7 0

It is a chemical change. Because energy was released and when a chemical change happens bonds are broken of formed.

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Question List (4 items) (Drag and drop into the appropriate area) Find the volume of HCl that will neutralize the base. Find the

expeople1 [14]

The question is incomplete, the complete question is:

The solubility of slaked lime, $Ca(OH)_2$ , in water is 0.185 g/100 ml. You will need to calculate the volume of $2.50\times 10^{-3}$ M HCl needed to neutralize 14.5 mL of a saturated

Answer: The volume of HCl required is 290mL, the mass of $Ca(OH)_2$ is 0.0268g, the moles of

Explanation:

Given values:

Solubility of $Ca(OH)_2$ = 0.185 g/100 mL

Volume of $Ca(OH)_2$ = 14.5 mL

Using unitary method:

In 100 mL, the mass of $Ca(OH)_2$ present is 0.185 g

So, in 14.5mL. the mass of $Ca(OH)_2$ present will be = $\frac{0.185}{100}\times 14.5=0.0268g$

The number of moles is defined as the ratio of the mass of a substance to its molar mass.

The equation used is:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$ ......(1)

Given mass of $Ca(OH)_2$ = 0.0268 g

Molar mass of $Ca(OH)_2$ = 74 g/mol

Plugging values in equation 1:

$\text{Moles of }Ca(OH)_2=\frac{0.0268g}{74g/mol}=0.000362 mol$

Moles of $OH^-$ present = $(2\times 0.000362)=0.000724mol$

The chemical equation for the neutralization of calcium hydroxide and HCl follows:

$Ca(OH)_2+2HCl\rightarrow CaCl_2+2H_2O$

By the stoichiometry of the reaction:

Moles of $OH^-$ = Moles of $H^+$ = 0.000724 mol

The formula used to calculate molarity:

$\text{Molarity of solution}=\frac{\text{Moles of solute}\times 1000}{\text{Volume of solution (mL)}}$ .....(2)

Moles of HCl = 0.000724 mol

Molarity of HCl = $2.50\times 10^{-3}$

Putting values in equation 2, we get:

$2.50\times 10^{-3}mol=\frac{0.000724\times 1000}{\text{Volume of solution}}\\\\\text{Volume of solution}=\frac{0.000725\times 1000}{2.50\times 10^{-3}}=290mL$

Hence, the volume of HCl required is 290mL, the mass of $Ca(OH)_2$ is 0.0268g, the moles of

5 0

3 years ago

(more then one answer) As a form of energy, light has specific properties such as color and brightness. Some properties can only

Lelu [443]

Answer:

Light travels in a straight line until it strikes an object.

As white light passes through a prism , it bends and separates into different colors

3 0

3 years ago

Read 2 more answers

The model on the right looks bumpy, but when you break a large salt crystal in two, the edges of the split often look straight a

emmasim [6.3K]

There is no problem with the model formed by atoms as solid spheres for macroscopic measurements because the atoms are extremely small.

<h3>What is Dalton's atomic model?</h3>

This was formulated in 1808 and states that atoms with spheres cannot be divided. It also states that solids are formed by contact between the spheres and chemical compounds from joining of atoms of two or more elements.

The size of the atoms in the form of sphere is very small as it is known that it is of the order of 10⁻⁹ m, therefore, having a macroscopic crystal more than 10⁻⁶ m in length which is why the model of the atom as solid spheres for macroscopic measurements has no problem.

Read more about Dalton's atomic theory here brainly.com/question/13157325

#SPJ1

5 0

1 year ago

The method used in this experiment is sometimes called the vapor density method. The ideal gas equation can be rearranged to sol

TiliK225 [7]

The correct answer for the question that is being presented above is this one: "B) Temperature."
Here are the following choices:

A) all of these measurements are needed

B) Temperature

C) Molar Mass

D) Pressure

E) Mass

6 0

3 years ago

If 84.1 g of NaOH and 51.0 g of Al and 25.0 g H20 react which chemical is the limiting reactant?

12345 [234]

Answer:

H₂O

Explanation:

1. Chemical quation

The reaction of aluminium, sodium hydroxide and water is represented by the balanced chemical equation:

2Al(s) + 2NaOH(s) + 6H₂O(l) → 2Na[Al(OH)₄] (aq) + 3H₂(g) ↑

The coefficients of each reactant and product give the theoretical mole ratios.

To find the limiting reactant you compare the theoretical ratios with the ratio of the available substaces.

2. Theoretical mole ratio:

2 mol Al : 2 mol NaOH : 6 mol H₂O

Equivalent to

1 mol Al : 1 mol NaOH : 3 mol H₂O

3. Actual ratio

a) Convert each mass to number of moles

Formula:

number of moles = mass in grams / molar mass

Al:

molar mass = atomic mass = 26.982g/mol

number of moles = 51.0g / 26.982g/mol = 1.89 mol

NaOH:

molar mass = 39.997g/mol

number of moles = 84.1g / 39.997g/mol = 2.10 mol

H₂O:

molar mass = 18.015g/mol

number of moles = 25.0g / 18.015g/mol = 1.39 mol

Divide all the mole amounts by the least number:

Al: 1.89/1.39 = 1.36
NaOH: 2.10 = 1.52
H₂O: 1.39 = 1.00

1.36 mol Al : 1.52 mol NaOH : 1.00 mol H₂O

4. Comparison

Theoretical ratio:

1 mol Al : 1 mol NaOH : 3 mol H₂O

Actual ratio:

1.36 mol Al : 1.52 mol NaOH : 1.00 mol H₂O

Multiply by 3:

4.08 mol Al : 4.56 mol NaOH : 3.00 mol H₂O

Now, yo can see that the first two are in excess with respect the third one, making that the water consumes first, before any of the other two consumes. Therefore, the limiting reactant is the water.

8 0

3 years ago