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2 years ago

Which material has a crystalline structure at room temperature ( 20 degrees Celsius )

Chemistry

2 answers:

Sauron [17]2 years ago

8 0

It's 2, glass. Water, nitrogen, and sucrose don;t have a crystalline structure.

Musya8 [376]2 years ago

8 0

Answer:

Sucrose. Option 4 is correct.

Explanation:

Crystallinity can be defined as the degree of structural order in a solid.

Let us take a look at each of the material mentioned in the question..

The first one is WATER. Water has the molecular formula of H2O, it is bent at an angle approximately 104.5 degrees. Because of its molecular form as liquid, WATER is amorphous and NOT crystalline.

The second material is GLASS: GLASS do not crystallized when they become hardened.

The third material is Nitrogen, NITROGEN is a non metallic element of group 15. Although solid nitrogen have crystalline modifications, they still exist as amorphous.

The fourth material is sucrose. SUCROSE is a disaccharide. It is a crystalline white solid.

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A 17.0-g sample of hf is dissolved in water to give 2.0 x 10 2 ml of solution. the concentration of the solution is:

fredd [130]

The concentration of the solution is 4.25 M

Explanation

molarity=moles/volume in liters

moles = mass/molar mass
molar mass of HF = 19 + 1 = 20 g/mol
moles is therefore = 17.0 g/ 20 g/mol = 0.85 moles

volume in liters = 2 x10^2ml/1000 = 0.2 liters

therefore molarity = 0.85/0.2 = 4.25 M

8 0

2 years ago

Read 2 more answers

Given that the density of TlCl(s) is 7.00 g/cm3 and that the length of an edge of a unit cell is 385 pm, determine how many form

ryzh [129]

Here's my best guess
the volume of the unit cell is (385*10^-12)^3=5.7066*10^-29 m^3
multiply by density to get mass mass = (7 g/cm^3)*(100^3 cm^3 / 1^3 m^3) * 5.7066*10^-29 m^3= 3.99466*10^-22 g
covert to moles 3.99466*10^-22 g * 1 mol / 239.82 g = 1.6657 *10^-24 mol
convert to number of units

1.6657 *10^-24 mol * 6.23*10^23 units/mol = 1.04

385 pm = 3.85*10^(-8) cm

The volume of the unit cell is the cube of that, which is 5.71*10^(-23) cm^3. Since the ratio of mass to volume (i.e. the density) must be the same no matter what amount of TlCl you have, you can say:
7 = x/(5.71*10^(-23)), where x is the mass of the unit cell. Solving for x, you get 4*10^(-22) g.

The mass of a molecule of TlCl is 240 amu, which in grams is 4*10^(-22) g. The mass of the unit cell and the mass of a molecule of TlCl is the same. Therefore there is one formula unit of TlCl per unit cell.

3 0

2 years ago

You can identify a metal by carefully determining its density. A 8.44 g piece of an unknown metal is 1.25 cm long, 2.50 cm wide,

Dafna1 [17]

Answer: Aluminum, $2.70 g/cm^3$

Explanation:

Density is defined as the mass contained per unit volume. It is characteristic of a substance.

$Density=\frac{mass}{Volume}$

Given : Mass of object = 8.44 grams

Volume of object= $length\times breadth\times height=1.25cm\times 2.50cm\times 1.0cm=3.125cm^3$

Putting in the values we get:

$Density=\frac{8.44g}{3.125cm^3}=2.70g/cm^3$

Thus density of the object will be $2.70 g/cm^3$ which matches that of aluminium.

4 0

2 years ago

Read 2 more answers

The first step in the Ostwald process for producing nitric acid is 4NH3(g) + 5O2(g) -> 4NO(g) + 6H2O(g). If the reaction of 1

aniked [119]

Answer: The percentage yield of the given reaction is 77.33%.

Explanation:

Moles is calculated by using the formula:

$Moles=\frac{\text{Given mass}}{\text{Molar mass}}$

Moles of Ammonia:

Given mass of ammonia = 150g

Molar mass of ammonia = 17 g/mol

Putting values in above equation, we get:

$\text{Moles of ammonia}=\frac{150g}{17g/mol}=8.82moles$

Moles of Oxygen

Given mass of oxygen = 150g

Molar mass of oxygen = 32 g/mol

Putting values in above equation, we get:

$\text{Moles of oxygen}=\frac{150g}{32g/mol}=4.6875moles$

For the given chemical equation:

$4NH_3(g)+5O_2(g)\rightarrow 4NO(g)+6H_2O(g)$

By Stoichiometry,

5 moles of oxygen reacts with 4 moles of ammonia.

So, 4.6875 moles of oxygen will react with = $\frac{4}{5}\times 4.6875=3.75moles$ of ammonia

As, moles of ammonia required is less than the calculated moles. Hence, ammonia is present in excess and is termed as excess reagent.

Therefore, oxygen is considered as a limiting reagent because it limits the formation of products.

By Stoichiometry of the given reaction:

5 moles of oxygen gas produces 4 moles of nitric oxide

So, 4.6875 moles of oxygen gas will produce = $\frac{4}{5}\times 4.6875=3.75moles$ of nitric oxide

Now, to calculate the theoretical amount of nitric oxide, we use equation 1:

Molar mass of nitric oxide = 30 g/mol

$3.75mol=\frac{\text{Given mass}}{30g/mol}$

Given mass of nitric oxide = 112.5 g

Now, to calculate the percentage yield, we use the formula:

$\%\text{ yield}=\frac{\text{Experimental yield}}{\text{Theoretical yield}}\times 100$

Experimental yield = 87 g

Theoretical yield = 112.5 g

Putting values in above equation, we get:

$\%\text{ yield}=\frac{87}{112.5}\times 100=77.33\%$

Hence, the percentage yield of the given reaction is 77.33%.

5 0

2 years ago

A sample of vinegar was found to have an acetic acid concentration of 0.8846 m. What is the acetic acid % by mass? Assume the de

jenyasd209 [6]

Answer:

5.3%

Explanation:

Let the volume be 1 L

volume , V = 1 L

use:

number of mol,

n = Molarity * Volume

= 0.8846*1

= 0.8846 mol

Molar mass of CH3COOH,

MM = 2*MM(C) + 4*MM(H) + 2*MM(O)

= 2*12.01 + 4*1.008 + 2*16.0

= 60.052 g/mol

use:

mass of CH3COOH,

m = number of mol * molar mass

= 0.8846 mol * 60.05 g/mol

= 53.12 g

volume of solution = 1 L = 1000 mL

density of solution = 1.00 g/mL

Use:

mass of solution = density * volume

= 1.00 g/mL * 1000 mL

= 1000 g

Now use:

mass % of acetic acid = mass of acetic acid * 100 / mass of solution

= 53.12 * 100 / 1000

= 5.312 %

≅ 5.3%

3 0

2 years ago