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3 years ago

What is the molar mass of an element?

Chemistry

1 answer:

Vesnalui [34]3 years ago

8 0

The answer is: the mass of 6.02 x 1023 representative particles of the element.

The base SI unit for molar mass is kg/mol, but chemist more use g/mol (gram per mole).

For example, molar mas of ammonia is 17.031 g/mol.

M(NH₃) = Ar(N) + 3 · Ar(H) · g/mol.

M(NH₃) = 14.007 + 3 · 1.008 · g/mol.

M(NH₃) = 17.031 g/mol.

The molar mass (M) is the mass of a given substance (in this example ammonia) divided by the amount of substance.

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You are given a solution that is 518 mM lactose. You need to make up 4.5 L of 16.7 mM solution. What volume do you need to trans

OLga [1]

Answer:

The volume you need to transfer from the stock solution is 0.145 l

Explanation:

Since the number of moles of lactose in the volume of stock solution that you transfer will be the same as the number of moles of lactose in the final solution, you can use this expression:

number of moles in volume to transfer = number of moles in the final solution

Since number of moles = concentration * volume (if the concentration is expressed in molarity), then:

Ci * Vi = Cf * Vf

where:

Ci = concentration of the stock solution.

Vi = volume of the stock solution to be transferred.

Cf = concentration of the final solution

Vf = volume of the final solution

Then, replacing with the data:

518 mM * Vi = 16.7 mM * 4.5 l

Vi = 16.7 mM * 4.5 l / 518 mM

Notice that any concentration unit can be used, as long as the units of the concentration of the stock and final solution are the same.

4 0

3 years ago

Explain, in terms of particles, what happens when methane boils and why

Ronch [10]

Answer:Butane > ethane > methane, because between bigger molecules there are stronger van der Waals forces and also higher molar mass means they need to be given more energy to have enough kinetic energy to move quickly, freely in gas.

There are multiple butene isomers (Butene) and some (2-Butenes - cis and trans) actually have higher boiling point than n-Butane (there is also Isobutane, of course, with quite much lower boiling point than all of them) and some (1-Butene, Isobutylene) have lower, so this isn't really a fair or simple question. But on simplest level, it can again be said that 1-butene has lower boiling point because it has very similar shape but slightly lower molar mass (2H less) than n-butane.

Explanation:

3 0

2 years ago

B. The highly toxic gas phosgene is produced by the reaction CO(g) + Cl2(g) COCl2(g), ΔH = –108 kJ/mol. Use this reaction to ans

galben [10]

Answer:

I. Increasing pressure will allow more frequent successful collision between particles due to the particles being closer together.

II. Rate of reaction increases due to more products being made; as increased pressure favours the exothermic side of the equilibrium.

III. Increasing temperature provides particles lots of (Kinetic) energy, for more frequent successful collision due to the particles moving at a faster rate than before. However, favouring the endothermic side of the equilibrium due to lots of energy required to break and form new bonds.

IV. Rate of reaction increases due to increase temperature favouring both directions of the equilibrium - causing products to form faster.

Hope this helps!

6 0

2 years ago

The octane number of gasoline is a measure of octane activity. The octane activity is determined by comparing the engine perform

Semmy [17]

Answer:

A. True

Explanation:

The octane number is determined by comparing the characteristics of gasoline to isooctane (2,2,4-trimethylpentane) and heptane. The correct option is option A.

Basically, the higher the octane number, the greater the resistance of the gasoline to knocking.

4 0

2 years ago

A buffer contains significant amounts of ammonia and ammonium chloride.

Oksanka [162]

Answer:

a. HCl + NH₃ ⇄ NH₄Cl

b. KOH + NH₄⁺ ⇄ K⁺ + NH₃ + H₂O

Explanation:

A buffer system is made by a weak base (ammonia, NH₃) and its conjugate acid (ammonium ion NH₄⁺ coming from ammonium chloride NH₄Cl). Its function is to resist abrupt changes in the pH when acids or bases are added.

a. When aqueous hydrochloric acid is added, it reacts with the base of the buffer. The corresponding equation is:

HCl + NH₃ ⇄ NH₄Cl

b. When aqueous potassium hydroxide is added, it reacts with the acid of the buffer. The corresponding equation is:

KOH + NH₄⁺ ⇄ K⁺ + NH₃ + H₂O

8 0

3 years ago