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3 years ago

How many moles are in 25 grams of Li? How do you know?

Chemistry

1 answer:

Ipatiy [6.2K]3 years ago

8 0

Answer:

3.6mol Li

Explanation:

To get the amount of moles from the mass we divide the mass by the molar mass.

25g ÷ 6.941g/mol = 3.6mol Li

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13. What is the symbol for Enthalpy change?

OverLord2011 [107]

Answer:

Explanation:

13 ) symbol of enthalpy change = Δ H .

14 ) enthalpy change is nothing but heat absorbed or evolved .

During fusion enthalpy change

Δ H .= m Lf , m is mass and Ls is latent heat of fusion

During evaporation, enthalpy change

Δ H .= m Lv , m is mass and Lv is latent heat of evaporation

during temperature rise , enthalpy change

Δ H = m c Δ T

In case of gas , enthalpy change can be calculated by the following relation

Δ H = Δ E + W , Δ E is change in internal energy , W is work done by gas.

15 ) When enthalpy change is negative , that means heat is released to the environment .So reaction is called exothermic .

when heat is absorbed enthalpy change is positive . Reaction is endothermic.

5 0

3 years ago

It is easier to push a sofa across a rough surface like carpet than a smooth surface like a hardwood floor.

Gelneren [198K]

False, pushing a sofa on a hardwood floor would be easier than on carpet.

3 0

3 years ago

8. How much heat is released when 85.0 g of steam condense to liquid water?

sergeinik [125]

Answer:

199920J

Explanation:

Given parameters:

Mass of steam = 85g

Unknown:

Heat released when the liquid is condensed = ?

Solution:

The heat released by the substance is given as;

H = mL

H is the heat released

m is the mass

L is the latent heat of steam = 2352J/g

Heat released = 85 x 2352 = 199920J

3 0

3 years ago

At the start of a reaction, there are 0.0249 mol N2,

gladu [14]

Answer:

Explanation:

The reaction is given as:

$N_{2(g)} + 3H_{2(g)} \to 2NH_{3(g)}$

The reaction quotient is:

$Q_C = \dfrac{[NH_3]^2}{[N_2][H_2]^3}$

From the given information:

TO find each entity in the reaction quotient, we have:

$[NH_3] = \dfrac{6.42 \times 10^{-4}}{3.5}\\ \\ NH_3 = 1.834 \times 10^{-4}$

$[N_2] = \dfrac{0.024 }{3.5}$

$[N_2] = 0.006857$

$[H_2] =\dfrac{3.21 \times 10^{-2}}{3.5}$

$[H_2] = 9.17 \times 10^{-3}$

∴

$Q_c= \dfrac{(1.834 \times 10^{-4})^2}{(0.0711)\times (9.17\times 10^{-3})^3} \\ \\ Q_c = 0.6135$

However; given that:

$K_c = 1.2$

By relating $Q_c \ \ and \ \ K_c$ , we will realize that $Q_c \ \ < \ \ K_c$

The reaction is said that it is not at equilibrium and for it to be at equilibrium, then the reaction needs to proceed in the forward direction.

7 0

3 years ago

g Select the correct statements. I. Reduction is the loss of electrons, and oxidation is the gain of electrons II. Reduction is

Karolina [17]

Answer: The correct answer is Option D.

Explanation:

Reduction reaction is defined as the reaction in which a substance gains electrons. Here, the oxidation state of the substance decreases.

$X^{n+}+ne^-\rightarrow X$

Oxidizing agents are the agents that helps in the oxidation of other substance and itself gets reduced. These agents undergoes reduction reactions.

Oxidation reaction is defined as the reaction in which a substance looses its electrons. Here, oxidation state of the substance increases.

$X\rightarrow X^{n+}+ne^-$

Reducing agents are the agents that helps in the reduction of the other substance and itself gets oxidized. These agents undergoes reduction reactions.

Oxidation state is the number which is given to an atom when it looses or gains electron. It is written as a superscript. In a compound, the total charge is equal to the sum of the charges of all atoms in that compound. For Example: In $MnO_4^-$ , manganese has +7 oxidation number and oxygen has -2.

So, the charge on the compound = $[=7+(4\times (-2))]=-1$

Hence, the correct answer is Option D.

6 0

3 years ago