Does dissolution or crystallization produce heat?

Classify these substances. More than one answer may apply in each case.

enyata [817]

Answer: $H_2$ : Pure substance, Element

$O_2$ : Pure substance , Element

$H_2O$ : Pure substance, Compound

Explanation:

Element is a pure substance which is composed of atoms of similar elements.It can not be decomposed into simpler constituents using chemical reactions.Example: $H-2$ and $O_2$

Compound is a pure substance which is made from atoms of different elements combined together in a fixed ratio by mass.It can be decomposed into simpler constituents using chemical reactions. Example: $H_2O$

Heterogeneous Mixture : Mixture that has its different components mixed unevenly within the substance . Example: Air

Homogeneous Mixture : Mixture that has its different components mixed evenly within the substance. Example: sugar dissolved in water

3 0

4 years ago

What is the volume of 25 g of ethyl alcohol with a density of 0.79 g/mL?

Verdich [7]

Answer:

31.64...

Explanation:

The formula is volume is equal to mass over density.

So 25/0.79=31.64...

3 0

3 years ago

Which of the following illustrates the conservation of matter? A. SnO2 + H2 --> Sn + 2 H2O B. 2 C + O2 --> CO2 C. KOH + HB

olga2289 [7]

C. KOH + HBr → KBr + H₂O

Explanation:

The two equations above illustrates the conservation of matter. The law of conservation of matters states that

"in a chemical reaction, matter is neither created nor destroyed but transformed from one form to another".

By this law, we understand that the amount of a particular matter we are starting with should be the one we end with.

KOH + HBr → KBr + H₂O

Conserving Product Reactants

K 1 1

O 1 1

H 2 2

We can see that the amount on both sides are the same.

Learn more:

Conservation of matter brainly.com/question/2190120

#learnwithBrainly

8 0

3 years ago

Indicate whether the following balanced equations involve oxidation-reduction. Check all that apply. Check all that apply. 2H2SO

guapka [62]

Answer : The balanced equations involve oxidation-reduction are:

(a) $2H_2SO_4(aq)+2NaBr(s)\rightarrow Br_2(l)+SO_2(g)+Na_2SO_4(aq)+2H_2O(l)$

(b) $3SO_2(g)+2HNO_3(aq)+2H_2O(l)\rightarrow 3H_2SO_4(aq)+2NO(g)$

(c) $NaI(aq)+3HOCl(aq)\rightarrow NaIO_3(aq)+3HCl(aq)$

Explanation :

Redox reaction or Oxidation-reduction reaction : It is defined as the reaction in which the oxidation and reduction reaction takes place simultaneously.

Oxidation reaction : It is defined as the reaction in which a substance looses its electrons. In this, oxidation state of an element increases. Or we can say that in oxidation, the loss of electrons takes place.

Reduction reaction : It is defined as the reaction in which a substance gains electrons. In this, oxidation state of an element decreases. Or we can say that in reduction, the gain of electrons takes place.

(a) The given chemical reaction is:

$2H_2SO_4(aq)+2NaBr(s)\rightarrow Br_2(l)+SO_2(g)+Na_2SO_4(aq)+2H_2O(l)$

This reaction involve oxidation-reduction reaction because the oxidation state bromine changes from (-1) to (0) which shows oxidation and sulfur changes from (+6) to (+4) which shows reduction.

(b) The given chemical reaction is:

$3SO_2(g)+2HNO_3(aq)+2H_2O(l)\rightarrow 3H_2SO_4(aq)+2NO(g)$

This reaction involve oxidation-reduction reaction because the oxidation state sulfur changes from (+4) to (+6) which shows oxidation and nitrogen changes from (+5) to (+2) which shows reduction.

(c) The given chemical reaction is:

$NaI(aq)+3HOCl(aq)\rightarrow NaIO_3(aq)+3HCl(aq)$

This reaction involve oxidation-reduction reaction because the oxidation state iodine changes from (-1) to (+5) which shows oxidation and chlorine changes from (+5) to (-1) which shows reduction.

(d) The given chemical reaction is:

$PBr_3(l)+3H_2O(l)\rightarrow H_3PO_3(aq)+3HBr(aq)$

This reaction does not involve oxidation-reduction reaction because the oxidation state of element present on reactant and product side are same.

3 0

3 years ago

Please help with whatever this is and go in number order

Alenkinab [10]

1.a- sodium(Na) b-nickel(Ni) c-iron (Fe)

6 0

3 years ago