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3 years ago

Which of the following is evidence of a chemical change?

Chemistry

2 answers:

krek1111 [17]3 years ago

5 0

the formation of a gas

larisa86 [58]3 years ago

5 0

Answer:

the formation of a gas

Explanation:

The chemical change is one in which some chemical reaction occur.

a) Phase change : it is simply change of one state of matter to another.

For example conversion of ice to liquid water, where there is no change in chemical composition of water and only the physical state is changing.

b) formation of gas: it is possible when some substance breaks into some other components or some substance reacts with other. This is definitely a chemical change as bonds will break and may be new bonds will form.

For example decomposition of calcium carbonate gives carbon dioxide (a gas) and calcium oxide.

c) mass change: it could be due to evaporation of water from a substance. Which must be a physical change.

d) surface area: change in surface is area must be due to change in state or physical modifications in state of a substance.

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Reactivity and flammability are are examples of properties.

nika2105 [10]

Answer:

they are eamples of chemical properties

Explanation:

flammibility is the chemical makeup of the element that makes it flamable and reactivitie is the chemical makeup of an element that is able to reacte to another element

3 0

3 years ago

Inside a flashbulb, oxygen surrounds a thin coil of magnesium. When the flashbulb is set off, a chemical reaction takes place in

hoa [83]

Answer:

Oxygen and magnesium come together in a chemical reaction to form this compound. After it burns, it forms a white powder of the magnesium oxide. Magnesium gives up two electrons to oxygen atoms to form this powdery product. This is an exothermic reaction.

6 0

3 years ago

Suppose you have 81.8 g of Cd. How many Cd atoms are present? Report your answer in scientific notation using the format of 6.02

Lostsunrise [7]

Answer:

1. number of Cd atoms = 4.384 × 10²³

2. number of moles of Ti = 0.817 mol

3. molar mass of C₇H₆O₃ = 138.077 g/mol

4. moles of Sildenafil = 0.249 mmol

Explanation:

1. given data

mass of Cd = 81.8 g

number of Cd atoms = ?

molar mass of Cd = 112.411 g/mol

Solution

1st we find out the number of moles of Cd

number of moles = mass / molar mass

number of moles of Cd = 81.8 g / 112.411 g.mol⁻

number of moles of Cd = 0.728 mol

Now we find out the number of Cd atoms

number of atoms = moles × 6.022 × 10²³

number of Cd atoms = 0.728 (6.022 × 10²³)

number of Cd atoms = 4.384 × 10²³

2. Given data

Mass of Ti = 39.1 g

moles = ?

molar mass Ti = 47.867 g/mol

Solution

Now we will find out the number of moles

number of moles = mass / molar mass

number of moles of Ti = 39.1 g / 47.867 g.mol⁻

number of moles of Ti = 0.817 mol

3. Given data

chemical formula of Salicylic acid = C₇H₆O₃

molar mass of salicylic acid = ?

molar mass of carbon = 12.011

molar mass of hydrogen = 1.008

molar mass of oxygen = 15.999

molar mass of molecule = number of moles of atoms × molar mass of atoms

molar mass of C₇H₆O₃ = 7 (12.011) + 6 (1) + 3 (16)

molar mass of C₇H₆O₃ = 84.077 g + 6 g + 48 g

molar mass of C₇H₆O₃ = 138.077 g/mol

4. Given data

molar mass of Sildenafil = 474.5828 g/mol

mass given = 0.118 g

moles of Sildenafil = ?

Solution

Now we find out the number of moles

number of moles = mass / molar mass

number of moles Sildenafil = 0.118 g / 474.5828 g/mol

number of moles Sildenafil = 0.0003 mol

as this is very small amount we convert it into millimoles

millimoles = moles × 1000

millimoles of Sildenafil = 0.000249 × 1000

millimoles of Sildenafil = 0.249 mmol

4 0

3 years ago

An atom is described as a nucleus of protons and neutrons surrounded by a

Vlad1618 [11]

Answer:

Explanation:

The nucleus (center) of the atom contains the protons (positively charged) and the neutrons (no charge). The outermost regions of the atom are called electron shells and contain the electrons (negatively charged). Atoms have different properties based on the arrangement and number of their basic particles.

6 0

3 years ago

Read 2 more answers

If an atom should form from its constituent particles,

tia_tia [17]

Answer:

(b) matter is lost and energy is released

Explanation:

When atoms are being formed from its constituent components it weighs less this is called mass defect so the answer would be (b) matter is lost and energy is released.

8 0

3 years ago