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2 years ago

Which quantity is equivalent to 39 grams of LiF?

Chemistry

2 answers:

Nutka1998 [239]2 years ago

3 0

I think that it is 1.5 mole it might not be

stich3 [128]2 years ago

3 0

Answer:

This question is incomplete, the completed question is below.

Which quantity is equivalent to 39 grams of LiF?

(a) 1.0 mole

(b) 2.0 mole

(d) 1.5 mole

The correct option is d

Explanation:

LiF is Lithium flouride. Lithium (Li) has a molar mass of 7 g/mol while flourine (F) has a molar mass of 19 g/mol. Hence, 1 mole of LiF will be

7 + 19 = 26 g/mol

If 1 mole of LiF = 26g,

X mole of LiF = 39g

When you cross multiply, you will have

X mole x 26g = 1 mole x 39g

make X the subject and you will have

X mole = 1 mole x 39g/26g

X mole = 1.5 mole

Hence, 1.5 mole of LiF is equivalent to 39 grams of LiF

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2 years ago

Which of the following statements describe chemical properties?

Y_Kistochka [10]

Answer:

A. Oxygen gas supports combustion.

B. Hydrofluoric acid reacts with glass.

C. Fertilizers help to increase agricultural production.

Explanation:

Chemical properties can only be observed when a chemical change, i.e. a change in the chemical composition, occurs.

On the other hand, physical properties are observed or measured without altering the composition of the substances.

Typical examples of chemical properties are reactivity, flammability, combustion, oxidation states, acidity, among others that require to carry out a chemical reaction to be observed.

Typical examples of physical properties are freezing point, melting point, boiling point, density, solubility, corrosiveness, among others.

Thus, as for the choices you have:

A. Oxygen gas supports combustion: the only way to observe this property is by carrying out a combustion reaction, so this describes a chemical property.

B. Hydrofluoric acid reacts with glass: again, only by letting hydrofluoric acid react with glass this can be observed, so this is another example of a chemical property.

C. Fertilizers help to increase agricultural production: fertilizers are absorbed by the plants and converted by biochemical reactions, so this also describes a chemical property.

D. Water boils below 100°C on top of a mountain: boiling is a change of state, the water is H₂O and continues having the same composition after boiling, so this describes a physical property.

E. Lead is denser than aluminum: density is measured by physical media, measuring mass and volume; so this is a physical property.

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2 years ago

Draw a structure containing only carbon and hydrogen that is a stable alkyne of five carbons containing a ring.

stepladder [879]

Answer:

Ethynylcyclopropane is the stable isomer for given alkyne.

Explanation:

In order to solve this problem we will first calculate the number of Hydrogen atoms. The general formula for alkynes is as,

CₙH₂ₙ₋₂

Putting value on n = 5,

C₅H₂.₅₋₂

C₅H₈

Also, the statement states that the compound contains one ring therefore, we will subtract 2 hydrogen atoms from the above formula i.e.

C₅H₈ ------------(-2 H) ----------> C₅H₆

Hence, the molecular formula for given compound is C₅H₆

Below, 4 different isomers with molecular formula C₅H₆ are attached.

The first compound i.e. ethynylcyclopropane is stable. As we know that alkynes are sp hybridized. The angle between C-C-H in alkynes is 180°. Hence, in this structure it can be seen that the alkyne part is linear and also the cyclopropane part is a well known moiety.

Compounds 3-ethylcycloprop-1-yne, cyclopentyne and 3-methylcyclobut-1-yne are highly unstable. The main reason for the instability is the presence of triple bond in three, five and four membered ring. As the alkynes are linear but the C-C-H bond in these compound is less than 180° which will make them highly unstable.

5 0

2 years ago

What features of this model will help Armando answer the question?

Scrat [10]

Answer:

The adjustable legs and the table of sand.

Note:The question is incomplete. The complete question is given below.

Using Models to Answer Questions About Systems

Armando’s class was looking at images of rivers formed by flowing water. Most of the rivers were wide and shallow, but one river was narrow and deep. Armando’s class thinks that this river is narrow and deep because:

the hill that the water flowed down was very steep, or
the sand grains that the water flowed through were very small.

Armando designed the model below to try to answer the question: Why is this river so narrow and deep?

Explanation:

The model designed by Armando will be helpful to answer the question because of the following features it possesses:

1. An adjustable leg- since one of the hypotheses put forward by the class to explain why the river was narrow and deep was that the hill that the water flowed down was very steep, the adjustable legs can be lowered or raised in order to make the slope shallower or steeper so that their hypothesis can be tested.

2. A table of sand- the table of sand serves as the streambed. By adjusting the size of the sand grains to be larger or smaller, the students will be able to to test their second hypothesis that the small size sand grains that the water flowed through was the reason for the river to be narrow and deep.

The results of their experiments will enable them to come to a conclusion.

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2 years ago

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