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2 years ago

Describe how a chemical change follows the law of conservation of matter. give examples pls

Chemistry

1 answer:

Paha777 [63]2 years ago

5 0

Explanation:

In any chemical change, one or more initial substances change into a different substance or substances. ... According to the law of conservation of matter, matter is neither created nor destroyed, so we must have the same number and kind of atoms after the chemical change as were present before the chemical change

Example:

The carbon atom in coal becomes carbon dioxide when it is burned. The carbon atom changes from a solid structure to a gas but its mass does not change.

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Chlorine can be prepared in the laboratory by the reaction of manganese dioxide with hydrochloric acid. HCl(aq), as described by

melisa1 [442]

Answer:

0.88 g

Explanation:

Using ideal gas equation to calculate the moles of chlorine gas produced as:-

$PV=nRT$

where,

P = pressure of the gas = 805 Torr

V = Volume of the gas = 235 mL = 0.235 L

T = Temperature of the gas = $25^oC=[25+273]K=298K$

R = Gas constant = $62.3637\text{torr}mol^{-1}K^{-1}$

n = number of moles of chlorine gas = ?

Putting values in above equation, we get:

$805torr\times 0.235L=n\times 62.3637\text{ torrHg }mol^{-1}K^{-1}\times 298K\\\\n=\frac{805\times 0.235}{62.3637\times 298}=0.01017\ mol$

According to the reaction:-

$MnO_2+4HCl\rightarrow MnCl_2+2H_2O+Cl_2$

1 mole of chlorine gas is produced when 1 mole of manganese dioxide undergoes reaction.

So,

0.01017 mole of chlorine gas is produced when 0.01017 mole of manganese dioxide undergoes reaction.

Moles of $MnO_2$ = 0.01017 moles

Molar mass of $MnO_2$ = 86.93685 g/mol

So,

$Mass=Moles\times Molar\ mass$

Applying values, we get that:-

$Mass=0.01017moles \times 86.93685\ g/mol=0.88\ g$

<u>0.88 g of $MnO_2(s)$ should be added to excess HCl (aq) to obtain 235 mL of $Cl_2(g)$ at 25 degrees C and 805 Torr.</u>

6 0

3 years ago

What’s are the different Types of chemical weathering

Ira Lisetskai [31]

Answer:

Types of chemical weathering

1. Hydrolysis

2. Oxidation

3. Carbonation

4. Acid rain

5. Acids produced by lichens

Explanation:

Chemical weathering occurs when rocks undergo chemical reactions to form new minerals.

Hydrolysis : is when water dissolves minerals present in rocks forming new compounds.

Oxidation : is when oxygen reacts with rocks eg. rust formation

Carbonation : it uses an acid known as carbonic acid, it is important in the formation of many caves and sinkholes.

8 0

3 years ago

When a solution of lead(II) nitrate is mixed with a solution of sodium chromate, a yellow precipitate forms. (a) Enter the balan

Damm [24]

Answer:

a) Pb(NO₃)₂(aq) + Na₂Cr₂O₄(aq) ⇄ 2NaNO₃(aq) + Pb(Cr₂O₄)(s)

b) 67.6%

Explanation:

a) Nitrate is the ion NO₃⁻, and lead(II) forms the ion Pb⁺², so the compound lead(III) nitrate is Pb(NO₃)₂. (First, the cation, then the anion, with charges replaced without the signal).

Chromate is the ion Cr₂O₄⁻² and sodium forms the ion Na⁺, so the sodium chromate is Na₂Cr₂O₄. Both of them are in solutions, so they will be in an aqueous state.

In the reaction, the anions and cations will replace and will form: NaNO₃ and Pb(Cr₂O₄). The nitrates formed by metals from group 1, such as sodium, are soluble, so it will not forme a precipitated. So, the precipitated is PbCr₂O₄, and the balanced reaction is:

Pb(NO₃)₂(aq) + Na₂Cr₂O₄(aq) ⇄ 2NaNO₃(aq) + Pb(Cr₂O₄)(s)

b) The molar masses are: Pb(NO₃)₃ = 331,2 g/mol; Na₂Cr₂O₄ = 162 g/mol; Pb(Cr₂O₄) = 323,2 g/mol.

First, let's find what is the limiting reactant, doing the stoichiometry calculus for the reactants. Let's suppose that Na₂Cr₂O₄ is the limiting so:

1 mol of Pb(NO₃)₂ ------------------------------ 1 mol of Na₂Cr₂O₄

Transforming to mass (mass = moles * molar mass):

331,2 g of Pb(NO₃)₂ ------------------------- 162 g/mol of Na₂Cr₂O₄

x ------------------------- 12.38

By a simple direct three rule:

162x = 4100.256

x = 25.3 g of Pb(NO₃)₂

This is higher than what is put in the reaction, so Pb(NO₃)₂ is the limiting reactant, and Na₂Cr₂O₄ is in excess. So, let's do the stoichiometric calculus for the limiting reactant and the solid formed:

1 mol of Pb(NO₃)₂ ----------------------- 1 mol of Pb(Cr₂O₄)

Transforming to mass:

331.2 g of Pb(NO₃)₂ ------------------- 323.2 g of Pb(Cr₂O₄)

11.39 g ------------------- y

By a simple direct three rule:

331.2 y = 3681.248

y = 11.115 g

The yield is the mass formed divided by the stoichiometric result multiplied by 100%:

yield = (7.52/11.115)*100% = 67.6%

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3 years ago

Rita was sitting in the garden and reading a book a sudden breeze went by her and she sneezed this reaction is a type of __ ? ac

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Involuntary and the brain, because the stem controls involuntary reactions

6 0

3 years ago

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Rock candy is a type of candy made by dissolving sugar in hot water and then cooling the solution so that large sugar crystals f

Elis [28]

Answer:

id think b but im not 100% sure if you get it wrong im sorry

8 0

3 years ago