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Naddika [18.5K]
3 years ago
8

In one experiment, magnesium metal melts. In a second experiment, magnesium metal ignites as it combines with oxygen. Classify t

he change in each experiment as chemical or physical. Explain your reasoning.
Chemistry
1 answer:
joja [24]3 years ago
8 0

Answer:

magnesium metal melts = physical change

magnesium metal ignites = chemical change

Explanation:

<em>Physical changes</em> are those in which the identity of the subtance <u>remains unaltered</u>. No new compounds are formed. They involve generally changes in <u>agreggation states of matter</u>: solid, liquid or gas. The first experiment, in which magnesium metal melts is a physical change because it only changes the state of matter, from solid to liquid, but it is still magnesium metal.

Conversely, <em>chemical changes</em> involve atoms combinations to form new compounds. The second experiment, in which magnesium metal ignites, is a chemical change. After the change, magnesium metal is no longer the metal but a metal oxide.

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Light elements with an atomic number less than 20 generally have a neutron to proton ratio equal to
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Atomic elements consist of a nucleus that contains protons and neutrons. Protons carry a positive charge whilst neutrons are electrically neutral. In light elements with an atomic number less than 20, the neutron to proton ratio is generally equal to 1:1. This changes for heavier elements since the Coulomb interaction between many protons gets stronger and demands more neutrons for the nucleus to remain stable. 
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3 years ago
You are starting with 2 pounds of 30% acetic acid solution. You want to dilute
Tpy6a [65]

Answer:

The mass of water to be added is 2 pounds

Explanation:

The given parameters are;

The mass of the given solution = 2 pounds

The concentration of the given solution = 30%

The desired concentration of the solution = 15%

The mass, m of the acetic acid in the given solution = 30% × 2 pounds

m = 30/100 × 2 pounds = 0.6 pounds

To make a 15% acetic acid solution of acetic acid, the mass X of the required volume, is given as follows;

15% of X = 0.6 pounds

15/100 × X = 3/20 × 0.6 pounds

∴ The mass of the solution required  X = 0.6 × 20/3 = 4 pounds

The mass of the solution that will contain 0.6 pounds of acetic acid giving a 15% acetic acid solution is 4 pounds

Therefore, the mass of water to be added to the original solution to make the a 15% acetic acid solution is 2 pounds.

8 0
3 years ago
The reaction of hydrogen(g) with fluorine(g) to form hydrogen fluoride(g) proceeds as follows: H2(g) + F2(g) 2 HF(g) When 0.647
Nata [24]

<u>Answer:</u> The value of \Delta H for the reaction will be -537 kJ

<u>Explanation:</u>

To calculate the number of moles, we use the equation:

\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}

Given mass of hydrogen gas = 0.647 g

Molar mass of hydrogen gas = 2 g/mol

Putting values in above equation, we get:

\text{Moles of hydrogen gas}=\frac{0.647g}{2g/mol}=0.324mol

We are given:

Energy released for 0.324 moles of hydrogen reacted is 174 kJ

For the given chemical reaction:

H_2(g)+F_2(g)\rightarrow 2HF(g)

By Stoichiometry of the reaction:

When 0.324 moles of hydrogen gas is reacted, the energy evolved is 174 kJ

So, when 1 mole of hydrogen gas will react, the energy evolved will be = \frac{174kJ}{0.324mol}\times 1mol=537kJ

<u>Sign convention of heat:</u>

When heat is absorbed, the sign of heat is taken to be positive and when heat is released, the sign of heat is taken to be negative.

Hence, the value of \Delta H for the reaction will be -537 kJ

6 0
3 years ago
Two angles with measures (6x + 60) (90)<br> are supplementary. What is the value of x?
fredd [130]
Supplementary angles add up to 180, so
6x+60+90 = 180 and solve for x
6x= 30
x=5
5 0
3 years ago
Read 2 more answers
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