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2 years ago

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When a sample is heated water is observed at the top of the tube. The compound melts and changes color. Te residue is not entire

ly soluble. It is most likely Select one: a. a carbohydrate b. a hydrate c. efflorescent d. deliquescent

1 answer:

harkovskaia [24]2 years ago

7 0

Answer:

hydrate

Explanation:

when a hydrate is heated,it changes color due to the exothermic reaction taking place.the structure of the complex changes but not entirely.this result in the sample to to not dissolve completely and we can observe the small traces of the sample.

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How can you tell if an element is a metal or nonmetal?

Nataly_w [17]

If you look on the periodic table (especially one online) you can see that it is colour coded...so this might help...

If you look you can see a "staircase"..which consists of B, Si, Ge, As, Sb, Te, Po...If it is on the lefthand side of the staircase it is a metal (ie: Ni) or if it is on the righthand side it is a non metal. There is lots of images on google that can help point it out.

If you are talking in terms of properties you should look for (Metal) materials that are:
<span>Lustrous
Hard.
High density (heavy for their size)
High strength (resist being stretched)
High melting and boiling points.
<span>Good conductors of heat and electricity.

Non metals are/have:
</span></span><span>High ionization
High electronegativities
Not malleable or ductile.
Little or no metallic luster.
Gain electrons easily.
<span>Dull, not metallic-shiny
</span></span>poor conductors of heat
and poor conductors of electricity

Hope this helps!

4 0

2 years ago

Read 2 more answers

Calculate the mass of methane that must be burned to provide enough heat to convert 242.0 g of water at 26.0°C into steam at 101

Anarel [89]

<u>Answer:</u> The mass of methane burned is 12.4 grams.

<u>Explanation:</u>

The chemical equation for the combustion of methane follows:

$CH_4(g)+2O_2(g)\rightarrow CO_2(g)+2H_2O(g)$

The equation for the enthalpy change of the above reaction is:

$\Delta H^o_{rxn}=[(1\times \Delta H^o_f_{(CO_2(g))})+(2\times \Delta H^o_f_{(H_2O(g))})]-[(1\times \Delta H^o_f_{(CH_4(g))})+(2\times \Delta H^o_f_{(O_2(g))})]$

We are given:

$\Delta H^o_f_{(H_2O(g))}=-241.82kJ/mol\\\Delta H^o_f_{(CO_2(g))}=-393.51kJ/mol\\\Delta H^o_f_{(CH_4(g))}=-74.81kJ/mol\\\Delta H^o_f_{O_2}=0kJ/mol$

Putting values in above equation, we get:

$\Delta H^o_{rxn}=[(1\times (-393.51))+(2\times (-241.82))]-[(1\times (-74.81))+(2\times (0))]\\\\\Delta H^o_{rxn}=-802.34kJ$

The heat calculated above is the heat released for 1 mole of methane.

The process involved in this problem are:

$(1):H_2O(l)(26^oC)\rightarrow H_2O(l)(100^oC)\\\\(2):H_2O(l)(100^oC)\rightarrow H_2O(g)(100^oC)\\\\(3):H_2O(g)(100^oC)\rightarrow H_2O(g)(101^oC)$

Now, we calculate the amount of heat released or absorbed in all the processes.

<u>For process 1:</u>

$q_1=mC_p,l\times (T_2-T_1)$

where,

$q_1$ = amount of heat absorbed = ?

m = mass of water = 242.0 g

$C_{p,l}$ = specific heat of water = 4.18 J/g°C

$T_2$ = final temperature = $100^oC$

$T_1$ = initial temperature = $26^oC$

Putting all the values in above equation, we get:

$q_1=242.0g\times 4.18J/g^oC\times (100-(26))^oC=74855.44J$

<u>For process 2:</u>

$q_2=m\times L_v$

where,

$q_2$ = amount of heat absorbed = ?

m = mass of water or steam = 242 g

$L_v$ = latent heat of vaporization = 2257 J/g

Putting all the values in above equation, we get:

$q_2=242g\times 2257J/g=546194J$

<u>For process 3:</u>

$q_3=mC_p,g\times (T_2-T_1)$

where,

$q_3$ = amount of heat absorbed = ?

m = mass of steam = 242.0 g

$C_{p,g}$ = specific heat of steam = 2.08 J/g°C

$T_2$ = final temperature = $101^oC$

$T_1$ = initial temperature = $100^oC$

Putting all the values in above equation, we get:

$q_3=242.0g\times 2.08J/g^oC\times (101-(100))^oC=503.36J$

Total heat required = $q_1+q_2+q_3=(74855.44+546194+503.36)=621552.8J=621.552kJ$

To calculate the number of moles of methane, we apply unitary method:

When 802.34 kJ of heat is needed, the amount of methane combusted is 1 mole

So, when 621.552 kJ of heat is needed, the amount of methane combusted will be = $\frac{1}{802.34}\times 621.552=0.775mol$

To calculate the number of moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$

Molar mass of methane = 16 g/mol

Moles of methane = 0.775 moles

Putting values in above equation, we get:

$0.775mol=\frac{\text{Mass of methane}}{16g/mol}\\\\\text{Mass of methane}=(0.775mol\times 16g/mol)=12.4g$

Hence, the mass of methane burned is 12.4 grams.

8 0

2 years ago

. how do some deep-sea animals use their bioluminescence, or ability to give off light? (select all that apply.)

nika2105 [10]

Answer:

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4 0

1 year ago

(25 hours ) /1 ( minutes) = ( hour )

Finger [1]

60 minutes
thanks again I appreciate you I'm sorry but you ok if I invite to you in my prayers for you and Mani

3 0

2 years ago

What is the conjugate acid in the following equation hbr + H2O yields h30 positive + BR negative

kirill115 [55]

Answer:

HBr + H2O = H3O+ + Br-

So our conjugate acid is the H3O+ to H2O

Explanation:

A conjugate acid of a base results when the base accepts a proton.

Consider ammonia reacting with water to form an equilibrium with ammonium ions and hydroxide ions:

NH3 (aq) + H2O (l) ⇌ NH4+ (aq) + OH- (aq)

Ammonium, NH4+, acts as a conjugate acid to ammonia, NH3.

3 0

2 years ago