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Doss [256]
3 years ago
11

A student added white crystals to a clear liquid. The crystals dissolved in the liquid. After a few seconds, the liquid became q

uite warm and then turned bright red in color. The first indication that a chemical change was taking place could be observed when----
Chemistry
1 answer:
Nuetrik [128]3 years ago
7 0

Answer:

Is when there is an increase in the temperature of the liquid

Explanation:

Increase in temperature of the liquid is an indication that chemical change occur because chemical change occur through process of chemical reaction and it involve when two or more substances combine together to form new substances which is as a result of change in chemical composition. The crystals dissolved in water to form another new solution and it became warm and this indicate a chemical change, new substances are formed as a result of increase in temperature.

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24. The air in a small 250 cm birthday balloon is at a pressure of 760 torr. A boy sits on it at
kvv77 [185]

Answer:

1.14atm

Explanation:

Given parameters:

V1 = 250cm³ ;

              1000cm³ = 1dm³;  so this is 0.25dm³

P1  = 760torr

            760torr  = 1atm

       

V2  = 220cm³ ; 0.22dm³

Unknown:

New pressure = ?

Solution:

To solve this problem, we apply Boyle's law and we use the expression below:

       P1 V1 = P2V2

The unknown is P2;

            1 x 0.25  = P2 x 0.22

                 P2  = 1.14atm

7 0
3 years ago
Rank the following in order of increasing (lowest to highest) reactivity:
choli [55]

Answer:

a)  Li<Na<Rb

b) P<S

c) Rn<Xe

d) Hg<W<Cs

4 0
3 years ago
1. Show that heat flows spontaneously from high temperature to low temperature in any isolated system (hint: use entropy change
Inga [223]

Answer:

1 ) Δs ( entropy change for hot block ) = - Q / th  ( -ve shows heat lost to cold block )

Δs ( entropy change for cold block ) = Q / tc

∴ Total Δs = ΔSc + ΔSh

                 = Q/tc - Q/th

2) ΔSdecomposition = Δh / Temp = ( 181.6 * 10^3 / 773 ) = 234.928 J/k

Explanation:

<u>1) To show that heat flows spontaneously from high temperature to low temperature </u>

example :

Pick two(2) solid metal blocks with varying temperatures ( i.e. one solid block is hot and the other solid block is cold )

Place both blocks for time (t ) in an insulated system to reduce heat loss or gain to or from the environment

Check the temperature of both blocks after time ( t ) it will be observed that both blocks will have same temperature after time t ( first law of thermodynamics )

Δs ( entropy change for hot block ) = - Q / th  ( -ve shows heat lost to cold block )

Δs ( entropy change for cold block ) = Q / tc

∴ Total Δs = ΔSc + ΔSh

                 = Q/tc - Q/th

<u>2) Entropy change for Decomposition of mercuric oxide </u>

2HgO (s) → 2Hg(l) + O₂ (g)

Δs = positive

there is transition from solid to liquid and the melting point of mercury ( the point at which reaction will take place ) = 500⁰C

hence ΔSdecomposition = S⁻ Hg  -  S⁻ HgO =

Δh of reaction = 181.6 KJ

Temp = 500 + 273 = 773 k

hence ΔSdecomposition = Δh / Temp = ( 181.6 * 10^3 / 773 ) = 234.928 J/k

8 0
3 years ago
Deuterium is the isotope of hydrogen of mass number 2, with a proton and a neutron in its nucleus. The chemistry of deuterium is
s344n2d4d5 [400]

Answer:

True

Explanation:

We know that the zero-point-energy of a C-D system is quite lower than the zero point energy of the C-H bond so the C-D bond is stronger.

Kinetic isotope effect refers to the change in the rate of reaction owing to a change of one of the atoms of the reactants by replacing it with one of its isotopes.

Since we know that the C-D bond is stronger than the C-H bond, when we replace hydrogen with deuterium in a reaction's rate determining step we experience a little lag in the rate of reaction. This is referred to as the kinetic isotope effect in physical organic chemistry.

6 0
3 years ago
Briefly describe four ways that a beam can be strengthened?​
lara31 [8.8K]

Answer:

1. Changing Beam Material

2. Corrugation

3. Changing Beam form

4. Steel Reinforcing Bars

Explanation:

Changing Beam Material

Some materials are stronger when used in beams than others. Beams made of steel for instance are stronger than beams made of wood. Therefore changing material can improve the strength of the beam. It is quite important to take into account the weights of the material though as different structures have different requirements.

Corrugation.

You can fold the beam into triangular shapes to increase strength. If you look at roofs you will notice that they are folded and this increased their strength. The same logic can be applied to beams.

Changing Beam Form

Another way to make Beams stronger is to change their form or rather their shape. Straight beams are not as strong as I-beams for instance. I-beams look like the capital letter I with the lines at both ends. I-beams are usually used in construction which shows that they are quite strong.

Steel Reinforcing Bars

When placed in concrete beams, Steel Reinforcing Bars which are also called Rebar can help strengthen a beam by helping it withstand the forces of tension. A concrete beam with Rebar inside it is known as Reinforced Concrete.

8 0
3 years ago
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