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dem82 [27]
2 years ago
13

How do you determine the number of moles in a sample

Chemistry
1 answer:
AleksandrR [38]2 years ago
3 0
Divide the mass of the compound in grams by the molar mass you just calculated. The answer is the number of moles of that mass of compound.
I hope it helps
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What does multivalent mean???
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In the context of multivalent ions, it is when it has multiple oxidative states. 
4 0
3 years ago
Consider the reaction directly below and answer parts a and b. C6H4(OH)2 (l) + H2O2 (l) à C6H4O2 (l) + 2 H2O (l)
dedylja [7]

Answer:

a. -206,4kJ

b. Surroundings will gain heat.

c. -115kJ are given off.

Explanation:

It is possible to obtain ΔH of a reaction using Hess's law that consist in sum the different ΔH's of other reactions until obtain the reaction you need.

Using:

<em>(1) </em>C₆H₄(OH)₂(l) → C₆H₄O₂(l) + H₂(g) ΔH: +177.4 kJ

<em>(2) </em>H₂(g) + O₂(g) → H₂O₂ (l) ΔH: -187.8 kJ

<em>(3) </em>H₂(g) + 1/2O₂(g) → H₂O(l) ΔH: -285.8 kJ

It is possible to obtain:

C₆H₄(OH)₂(l) + H₂O₂(l) → C₆H₄O₂(l) + 2H₂O(l)

From (1)-(2)+2×(3). That is:

<em>(1) </em>C₆H₄(OH)₂(l) → C₆H₄O₂(l) + H₂(g) ΔH: +177.4 kJ

<em>-(2) </em>H₂O₂(l) → H₂(g) + O₂(g) ΔH: +187.8 kJ

<em>2x(3) </em>2H₂(g) + O₂(g) → 2H₂O(l) ΔH: 2×-285.8 kJ

The ΔH you obtain is:

+177,4kJ + 187,8kJ - 2×285.8 kJ =<em> -206,4kJ</em>

b. When ΔH of a reaction is <0, the reaction is exothermic, that means that the reaction produce heat and the <em>surroundings will gain this heat.</em>

c. 20,0g of H₂O are:

20,0g×\frac{1mol}{18,01g} = <em>1,11 mol H₂O</em>

As 2 moles of H₂O are produced when -206,4kJ are given off, when 1,11mol of H₂O are produced, there are given off:

1,11mol H₂O×\frac{-206,4kJ}{2mol} =<em> -115kJ</em>

I hope it helps!

8 0
3 years ago
The atoms of a solid aluminum can are close together, vibrating in a rigid structure. If the can is warmed up on a hot plate, wh
Oksana_A [137]

Explanation:

Since atoms of solid aluminium can are closer to each other, therefore, when heat is supplied then transfer of energy in the form of heat will be faster.

As a result, when can is warmed up then atoms of solid aluminium can will start to vibrate more because heat will decrease the force of attraction between the molecules.

Thus, atoms will start to move away from each other and hence, they will vibrate more.

5 0
3 years ago
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3 years ago
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A first-order decomposition reaction has a rate constant of 0.00440 yr−1. How long does it take for [reactant] to reach 12.5% of
mina [271]

Answer:

473 year

Explanation:

Using integrated rate law for first order kinetics as:

[A_t]=[A_0]e^{-kt}

Where,  

[A_t] is the concentration at time t

[A_0] is the initial concentration

Given:

To reach 12.5% of reactant means that 0.125 of [A_0] is decomposed. So,

\frac {[A_t]}{[A_0]} = 0.125

t = ?

\frac {[A_t]}{[A_0]}=e^{-k\times t}

0.125=e^{-0.00440\times t}

t = 473 year

8 0
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