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3 years ago

Which of the following correctly describes a compound?

Chemistry

1 answer:

Nutka1998 [239]3 years ago

3 0

A compound is a pure substance formed by the chemical combination of two or more different elements.

A compound may be splitted into simpler substances by chemical reactions, and has different properties to those of the elements that form it.

The composition of a compound is fixed: every piece of a compound has the same kind of atoms, bonded in the same way and proportion.

Some examples of compounds are H₂O, NaCl, H₂O₂, CH₃COOH. As you see, they have a chemical formula which states the kind and number of the atoms that form them.

They are different to mixtures, which are formed by two or more compounds, in a variable proportion, and can be separated by physical media. Some examples of mixtures are the solutions (e.g. NaCl dissolved in H₂O), and some solid mixtures (e.g. a mixture of marbles and sand).

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142Pm > 142 Nd +<br> what is the answer to this equation

erastova [34]

Explanation:

nnbbnmkmknn bnnnbbtbbbbn' nn' t

4 0

2 years ago

1. NaOH mass of a solution of 200g in which its percentage is 25%. What mass of sulfuric acid solution is needed to completely n

Ede4ka [16]

Answer:

$m_{H2SO4$ = 61.25 g

$m_{Na2SO4}$ = 88.75 g

Explanation:

$m_{NaOH}$ = $\frac{200 . 25 }{100}$ = 50 g

⇒ $n_{NaOH}$ = $\frac{50}{40}$ = 1.25 (moles)

2NaOH + H2SO4 ⇒ Na2SO4 + 2H2O

2 : 1 : 1 : 2

1.25 (moles)

⇒ $n_{H2SO4}$ = 1.25 × 1 ÷ 2 = 0.625 (moles) ⇒ $m_{H2SO4}$ = 0.625 × 98 = 61.25 g

$n_{Na2SO4}$ = 1.25 × 1 ÷ 2 = 0.625 (moles) ⇒ $m_{Na2SO4}$ = 0.625 × 142 = 88.75 g

4 0

3 years ago

Chemistry omg need help plz I need plz. I real badly at it and try to get better but plz help me

Rufina [12.5K]

We all struggle in some subjects, you do badly when you don't try, and sometimes we try and can't get the answer, I'll help with that. :)

The first answer is CO2(g), CO2 is a gas, and all gas have... 4) No definite shape, no definite volume.

A piece of ice, a block of wood, and a ceramic cup are solids. They have shapes that do not change and volumes that can be measured. Any matter that is a solid has a definite shape and a definite volume.

A liquid takes the shape of what holds it, besides a flat surface, which will just evidently, take the shape of a flat surface. A liquid has a definite volume, because the volume of a liquid is constant because forces of attraction keep the particles loosely together.

Gases attempt to fill a container of any shape or size. Therefore, it has no definite shape.
There are forces of attraction among the particles in all matter, therefore, it has no definite volume.

The second question might become easier with the explanation above. A liquid has a definite volume because the forces of attraction are loosely together! Therefore, it has a definite volume, but it will take the shape of it's container.

This means... Yes! 2) It retains its original volume but changes shape.

This one is easy. To convert one gram of a solid at its normal heating point to a liquid at the same temperature, is the 1) Heat of Vaporization.

Heat of Vaporization is the amount of heat energy required to convert one gram of a substance from a liquid to a gas.

The third question, the molecules for H20, in a solid phase are always in an geometric and arranged pattern.

Most solids are arranged in geometric and arranged patterns, and since H20 is not in its indefinitely shaped liquid phase, it has a definite shape and thus, retains a repeating (geometric) pattern.

(Note- Some solids like wax or rubber do not have an arranged or geometric pattern.)

The “average of a kinetic energy” is defined as the vitality of movement of particles of a framework.

Or in simpler terms, “energy motion”.

So when temperature increases, the average kinetic energy of a molecule(s) 1) increases.

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7 0

3 years ago

How many moles of NO2 form when<br> 63.25 g N2O5 decompose?<br> 2N2O5→ 4NO2 + 0₂

GREYUIT [131]

Answer:

1.1713 moles

Explanation:

RFM of N2O5= (14*2)+(16*4)=108

Moles of N2O5= Mass/RFM= 63.25/108= 0.5856 moles

Mole ratio of N2O5:NO2 = 2:4

Therefore moles of NO2= 4/2*0.5856= 1.1713 moles

7 0

1 year ago

Write the formula for potassium oxide. why do you not need prefixes in the name

Molodets [167]

Potassium oxide: K₂O.

There's no need for prefixes since K₂O is an ionic compound.

<h3>Explanation</h3>

Find the two elements on a periodic table:

Potassium- K- on the left end of period four.
Oxygen- O- near the right end of periodic two.

Elements on the bottom-left corner of the periodic table are metals. Those on the top-right corner are nonmetals.

Potassium is a metal,
Oxygen is a nonmetal.

A metal and a nonmetal combine to form an ionic compound. Potassium oxide is likely to be an ionic compound. It contains two types of ions:

Potassium ions: Potassium is group 1 of the periodic table. It is an alkaline metal. Like other alkaline metals such as sodium Na, potassium K tends to lose one electron and form ions of charge +1 in compounds. The ion would be K⁺.

Oxide ions from oxygen: Oxygen is the second most electronegative element on the periodic table. It tends to gain two electrons and form the oxide ion $\text{O}^{2-}$ when it combines with metals.

The two types of ions carry opposite charges. They shall pair up at a certain ratio such that they balance the charge on each other. The charge on each $\text{O}^{2-}$ ion is twice that on a $\text{K}^{+}$ ion. Each $\text{K}^{+}$ would pair up with two $\text{O}^{2-}$ . Hence the subscript in the formula: $\text{K}_{\bf 2}\text{O}$ .

There are two classes of compounds:

Covalent compounds, which need prefixes, and
Ionic compounds, which need no prefix.

Prefixes are needed only in covalent compounds. For instance in the covalent compound carbon dioxide $\text{CO}_2$ , the prefix di- indicates that there are two oxygen atoms in the formula $\text{CO}_2$ . However, there's no need for prefix in ionic compounds such as $\text{K}_2\text{O}$ .

7 0

3 years ago