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olya-2409 [2.1K]
3 years ago
7

Which of the following are indicators of a chemical change?

Chemistry
2 answers:
artcher [175]3 years ago
7 0
Hey there!
Chemical changes are changes in object's chemical compounds and chemical compositions, and often can't be reversed.
Here's an example:
If you have a piece of paper and you happen to burn it, that can't be reversed.
In other words, it can't be "un-burned". Nothing can restore it to its previous state.
Hopefully this helped!
kondaur [170]3 years ago
5 0
Change in color, temperature, or odor 
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Find the pH of a solution that has an H+ concentration of 2.5x10-3 M
Nastasia [14]

Answer:

The pH is 2, 60

Explanation:

The pH gives us an idea of the acidity or basicity of a solution. It is calculated as:

pH = -log (H +)= -log (2.5x10-3 )

<em>pH=2, 60</em>

7 0
3 years ago
What is the percent of H in NH3
ale4655 [162]

\frac{h3}{nh3}

\frac{1.008 \times 3}{(14.01) + (1.008 \times 3)}  \times 100\% =
ok, now press calculator. i dont have it now.
6 0
3 years ago
Read 2 more answers
PLEASE I NEED HELP ASAP!!!!
miv72 [106K]

The percent yield of the calcium hydroxide is 84.5%.

<h3>What is stoichiometry?</h3>

Stoichiometry enables us to obtain the mass of a substance form the equation of the reaction.

The equation of the reaction is;

CaCO3 + 2HCl -----> CaCl2 + CO2 + H2O

Number of moles of X = 40.0 grams/100 g/mol = 0.4 moles

Number of moles of HCl = 850/1000 * 1 M = 0.85 moles

If 1 mole of CaCO3 reacts with 2 moles of HCl

0.4 moles of  CaCO3 reacts with  0.4 moles  * 2 moles/1 mole

= 0.8 moles of HCl

Hence X is the limiting reactant.

The reaction is 1:1 then the amount of CO2  produced is 0.4 moles

Mass of CO2 = 0.4 CO2 * 44 g/mol = 17.6 g

2) The reaction equation is; 2NaOH + CaCO3 --->  Ca(OH)2 + Na2CO3

Number of moles of X = 25.0 grams/100 g/mol =  0.25 moles

Number of moles of NaOH= 40/1000 L * 2 M = 0.08 moles

If 1 mole of X reacts with 2 moles of NaOH

0.25 moles  reacts with   0.25 moles   * 2 moles /1 mole

= 0.5 moles

NaOH is the limiting reactant

2 moles of NaOH produces 1 mole of CO2

0.08 moles of NaOH produces 0.08 moles * 1 mole/2 moles

= 0.04 moles of CO2

Theoretical yield of CO2 =  0.04 moles of CO2 * 74 g/mol = 2.96  g

Percent yield = 2.5 g/ 2.96  g * 100

= 84.5%

Learn ore about percent yield:brainly.com/question/17042787

#SPJ1

5 0
1 year ago
Base your answers on the graph below, which represents uniform cooling of a sample of a pure substance, starting as a gas. Solid
Karolina [17]

Answer:

D & E

Explanation:

I think this is dealing with latent heat and D & E would be the range where you will find solid and liquid phases in equilibrium, cuz it starts as gas at from A to B, B to C is gas and liquid equilibrium, C to D is liquid, D to E solid and liquid, and then E to F is solid.

7 0
3 years ago
What does plasma mean
Zinaida [17]
An ionized has consisting of positive ions and free elections in proportion resulting in more or less no overall electric charge
8 0
2 years ago
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