Classifying Chemical Reactions Lab Answers

Classifying Chemical Reactions LAB
Observations listed below for 7 reactions and QUESTIONS

Reaction 1:The zinc metal is dull to start with&disappears as the reaction proceeds.Bubbles form around zinc.
Reaction 2:hydrogen peroxide is colourless and MnO2(s)is black.The solution bubbles alot when MnO2(s)is added.The gas that is produced looks smoky causes the glowing splint to burst into flames.The solution remain colourless.

Reaction 3:copper wire is shiny to start with & glows red hot when in the burner flame.wire becomes dull after 2 min of heating.

Reaction 4:Both solutions are colourless to start with,but when mixed,they become milky in colour.

Reaction 5:The CuSO4*5H2O(s)is blue to start with & gradually turns white with heating.Drops of liquid form on neck of the test tube.

Reaction 6:white solid turns blue when few drops of H2O are added.test tube gets warmer after water is added.

Reaction 7:The iron nail is shiny to start with&the solution is blue.The nail gets a dark coating&the solution turns lighter blue with time.Closer look of nail shows a coppery colored substance on it.

1Write balanced equation for all 7 reactions including state of particpants(s,l,g) and classify reaction as synthesis,decomposition,SR,DR

2The copper wire in reaction 3 essentially burned in air.What part of the air did the copper react with?

3Cu+2(aq) ions are the cause of the blue colour in the copper(II) sulphate solution.In reaction7,what is indicated by the colour change in the solution?

4)2common observations where chemical change occured?

Asked on by stella01

5 Answers | Add Yours

ndnordic's profile pic

ndnordic | High School Teacher | (Level 2) Associate Educator

Posted on

Balanced Equations:

you did not state what was added to the Zn so lets assume HCl.

Zn (s) +2 HCl (aq) -->  ZnCl2 (aq) + H2 (g)  Single replacement

In the second reaction the MnO2 acts as a catalyst in the decomposition of hydrogen peroxide.

2 H2O2 (aq) --> 2 H2O (aq) + O2 (g)


Reaction 3 is a synthesis reaction:

2 Cu (s) + O2 (g) --> 2 CuO (s)


Reaction 4 is a double replacement reaction.  The general form is:

AB (aq) + CD (aq) --> AC (aq)  + BD (s)


reaction 5 is a decomposition or dehydration type reaction:

CuSO4*5HOH (s) --> CuSO4 (s) + 5 HOH (l)


Reaction 6 is a synthesis or hydration reaction:

CuSO4 (s) + 5 HOH (l) -->  CuSO4*5HOH (s)

Reaction 7 is a single replacement reaction and is also an oxidation-reduction reaction>  The iron is oxidized and the copper is reduced.

Fe (s) + CuSO4 (aq)--> FeSO4 (aq)+ Cu (s)

Question 2:  the copper is combining with the oxygen in the air.


Question 3: the copper ion is being reduced to the element so the blue color gradually disappears.

Question 4:  common signs of a chemical reaction are:  release of heat or a gas; formation of a precipitate; change in color.

msscience2004's profile pic

msscience2004 | High School Teacher | (Level 1) eNoter

Posted on

answer to question

5) The reaction between BaCl2 and Na2SO4 yields table salt as one of its product. Aside from this it also produces BaSO4 which is a white precipitate of the reaction. The milky white solid is BaSO4 (barium sulfate)

6) The two products are H2O which is known as the universal solvent. And molecular oxygen O2 which causes combustion reactions to proceed.

7) Since we are reacting two molecular hydrogen with oxygen the balance reaction would be:

2H2 + O2-----> 2H2O

read as: 2 moles of hydrogen in reaction wih molecular oxygen yields to 2 moles of water.

studytime15's profile pic

studytime15 | Student, Undergraduate | eNotes Newbie

Posted on

I have a question! Water can be decomposed into 2 common gases using the process of electrolysis. What would the balanced equation be for the reaction?

govindan's profile pic

govindan | College Teacher | (Level 2) eNoter

Posted on

The anwer 7) may be modified as:

2H2 (g) + O2 (g)  -----------> 2 H2O (l)

Which means that 2 moles of hydrogen molecules ( 4 g) reacts with 1 mole of oxygen ( 32 g) to form 2 moles of water (36) at Standard Temperature and Pressure.

stella01's profile pic

stella01 | Student, College Freshman | (Level 1) Honors

Posted on

yes it was HCl. Thank You. I have couple more questions

question 5)Table salt is one of the products in reaction 4.  As you know, table salt dissolves very well in water.  What is the chemical formula for the other product which causes the milky white solid to form?

6)There are two products in reaction 2. One is the most common liquid on the planet and the other caused the glowing splint to burst into flames. Identify each product?

7)The gas produced in reaction #1 is extremely flammable.  Write the balanced equation for the combustion of this substance

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