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3 years ago

Which of the following statements holds true for a chemical change

2 answers:

7 0

A chemical change takes place when reactants are consumed and converted into a product which is different in composition and characteristics from the initial compounds.

shusha [124]3 years ago

6 0

A chemical change is when the change is unseen. In other words, the change is between the bonds, which changes the substance completely.

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What is measured by the heat of reaction?

bixtya [17]

Answer:

The heat of reaction is basically the energy that is being released and or absorbed when chemicals are transformed in a type of chemical reaction. However, the heat of reaction or also called reaction enthalpy is mostly or typically expressed as a molar enthalpy in kJ/mol and or as just a specific enthalpy in kJ/kg or kJ/L.

6 0

3 years ago

Why are groups 1 and 2 referred to as the s-block of the periodic table

qwelly [4]

Answer: This is because their valence electrons are located in the S - orbital

Explanation:

This is because their valence electrons are located in the S - orbital.

3 0

3 years ago

What is the pH of a 75.0 mL solution that is 0.045 M in weak base and 0.053 M in the conjugate weak acid

noname [10]

Answer:

7.07

Explanation:

HA = weak acid = 0.053

A+ = conjugate base = 0.045

Ka = 7.2x10^-8

Ka = [H+][A-]/HA

7 2x10^-8 = [H+][0.045]/0.053

[H+] = 7.2x10^-8 x 0.053/0.045

= 8.48x10^-8

PH = -log[H+]

= -log[8.48x10^-8]

PH = -[login.48 + log10^-8]

PH = -0.928 - (-8)log10

= 7.07

3 0

3 years ago

The image shows the representation of an unknown element in the periodic table. A square is shown. Inside the square twelve is w

Ludmilka [50]

<u>Answer:</u> The correct answer is the mass number of the most common isotope of the element is 24.

<u>Explanation:</u>

We are given:

An element having atomic number 12 is magnesium and atomic mass of the element is 24.305

The image corresponding will be $_{24.305}\textrm{Mg}^{12}\\\text{Magnesium}$

The number '24.305' is the average atomic mass of magnesium element.

Average atomic mass is defined as the sum of masses of each isotope each multiplied by their natural fractional abundance.

Formula used to calculate average atomic mass follows:

$\text{Average atomic mass }=\sum_{i=1}^n\text{(Atomic mass of an isotopes)}_i\times \text{(Fractional abundance})_i$

Average atomic mass of magnesium = 24.305 amu

As, the average atomic mass of magnesium lies closer to the mass of Mg-24 isotope. This means that the relative abundance of this isotope is the highest of all the other isotopes.

The 'Mg-24' isotope is the most common isotope of the given element.

Hence, the correct answer is the mass number of the most common isotope of the element is 24.

4 0

3 years ago

A sample of a pure substance with a density of 3 g/mL is separated into two pieces. One piece has a mass of 50 g and the other p

pshichka [43]

Answer:

8.3ml

Explanation:

to get volume u have to divide 25g over the density, i rounded to the nearest tenth, if you don't want to then write out the full number with all the decimals

4 0

2 years ago