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3 years ago

Which of the following are phase changes? Select all that apply.

Chemistry

2 answers:

lidiya [134]3 years ago

5 0

Answer: Options A, B, C, and D are all representing phase changes.

Explanation:

Phase change means change in the state of a substance from one form to another that is change of a liquid into solid, liquid into gas and vice versa.

In liquid freezing, the liquid is changing into solid so here phase is changing.

In solid melting, solid is changing into liquid so here phase is changing.

In ice melting, solid is changing into liquid so here phase is changing.

In sublimation of a solid, the solid changes to gas without changing into liquid. So, here also phase is changing.

When paper is burning, it is a chemical change as a new substance is formed which cannot be reversed into paper again.

Therefore, options A, B, C, and D are all representing phase changes.

kogti [31]3 years ago

4 0

A, B, C, and D, because they are changing from a solid to a liquid, liquid to solid, and solid to gas. Phase changes are when a solid, liquid, or gas, turns into a solid, liquid, or gas. Ex. Ice melting is a solid changing into a liquid. Hope this helps!

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Zina [86]

Answer:

Explanation:

n CaCO3 = mass / m.wt

= 500 /( 40 + 12 + 16x 3)

= 5 mole

n CaO = 5 moles ( from the balanced equation we have 1:1 moles )

mass of CaO = nCaO X m.wt

5 x( 40 +16 )

= 280 grams

5 0

3 years ago

An element has ccp packing with a face-centered cubic unit cell. its density is 8920 kg/m3 and the unit cell volume is 4.72 x 10

ziro4ka [17]

<span>63.4 g/mol
First, let's determine how many atoms per unit cell in face-centered cubic. There is 8 corners, each of which has 1 atom, and each of those atoms is shared between 8 other unit cells. So 8*1/8 = 1 atom per unit cell. Additionally, there are 6 faces, each of which has 1 atom that's shared between 2 unit cells. So 6*1/2 = 3 atoms per unit cell. So each unit cell has the mass of 1+3 = 4 atoms. Since there is 1000 liters per cubic meter, the mass per liter is 8920 kg/1000 = 8.920 kg/L. Now the mass per unit cell is 8920 g * 4.72x10^-26 = 4.21024x10^-22 g per unit cell. The mass per atom is 4.21024x10^-22 g / 4 = 1.05256x10^-22 g/atom, Finally, multiply by Avogadro's number, getting 1.05256x10^-22 g/atom * 6.0221409x10^23 atom/mol = 63.38664625704 g/mol.
Rounding to 3 significant digits gives 63.4 g/mol.</span>

5 0

3 years ago

If a sample containing 18.1 g of NH3 is reacted with 90.4 g of

USPshnik [31]

Answer:

3.64g

Explanation:

Given parameters:

Mass of NH₃ = 18.1g

Mass of Cu₂O = 90.4g

Unknown:

Limiting reactant = ?

Mass of N₂ formed = ?

Solution:

The reaction equation is given as:

Cu₂O + 2NH₃ → 6Cu + N₂ + 3H₂O

The limiting reactant is the one in short supply in the reaction. Let us find the number of moles of the given species;

Number of moles = $\frac{mass}{molar mass}$

Molar mass of Cu₂O = 2(63.6) + 16 = 143.2g/mol

Molar mass of NH₃ = 14 + 3(1) = 17g/mol

Number of moles of Cu₂O = $\frac{18.1}{143.2}$ = 0.13moles

Number of moles of NH₃ = $\frac{90.4}{17}$ = 5.32moles

From this reaction;

1 mole of Cu₂O combines with 2 mole of NH₃

So 0.13moles of Cu₂O will combine with 0.13 x 2 mole of NH₃

= 0.26moles of NH₃

Therefore, Cu₂O is the limiting reactant. Ammonia is in excess;

Mass of N₂;

Mass = number of moles x molar mass

1 mole of Cu₂O will produce 1 mole of N₂

0.13 mole of Cu₂O will produce 0.13 mole of N₂

Mass = 0.13 x (2 x 14) = 3.64g

5 0

3 years ago

If the pressure of a gas is 1.01 atm and the temperature is 25°C, then if the pressure is increased to 1.10, what is the new tem

vodka [1.7K]

Answer:

T2 = 51.6°C

Explanation:

Given:

P1 = 1.01 atm

T1 = 25°C + 273 = 298K

P2 = 1.10 atm

T2 = ?

P1/T1 = P2/T2

Solving for T2,

T2 = (P2/P1)T1

= (1.10 atm/1.01 atm)(298K)

= 324.6 K

= 51.6°C

where Tc = Tk - 273

3 0

3 years ago

The mass number of an element is equal to ____.

melisa1 [442]

Mass number is the total number of protons and neutrons in the nucleus

4 0

3 years ago

Read 2 more answers