1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
Ugo [173]
3 years ago
7

a chemist is studying an unknown substance he can break it into its elemental only by using chemical means.Based on this observa

tion, how should the unknown substance be classified
Chemistry
1 answer:
Vanyuwa [196]3 years ago
4 0

Answer:

Compound

Explanation:

We want to know if it's a compound or a mixture.

An example of a mixture is salt water: you can heat it hot enough to boil off the water, leaving only the salt. This is a physical change, which is how you know it's a mixture.

Something like gold is a compound: if you heat it, or hit it, you'll still only have gold. You can only break it down by chemical means, which is how you know it's a compound.

You might be interested in
Can swords shatter from cold temperatures
sp2606 [1]
Depends on how the sword is made, what materials are used and temperature used but yes they can shatter.

When molecules cool down they stop vibrating and moving as much and so they "shrink" and the metal of the sword becomes brittle. sometimes they shrink at different phases which cause tension in the sword if this tension is strong enough it can cause the metallic bonds to break causing the sword to shatter.

hope that helps 
6 0
3 years ago
Which can not be decomposed by a chemical change? 1) a compound 2) a heterogeneous mixture 3) a homogeneous mixture 4) an elemen
Mnenie [13.5K]
4.) an element cannot be decomposed by a chemical change, it is a pure substance and no other materials compose it.
3 0
3 years ago
Calculate the standard enthalpy change for the reaction at 25 ∘ C. Standard enthalpy of formation values can be found in this li
Anastasy [175]

Answer:

-179.06 kJ

Explanation:

Let's consider the following balanced reaction.

HCl(g) + NaOH(s) ⟶ NaCl(s) + H₂O(l)

We can calculate the standard enthalpy change for the reaction (ΔH°r) using the following expression.

ΔH°r = 1 mol × ΔH°f(NaCl(s)) + 1 mol × ΔH°f(H₂O(l)) - 1 mol × ΔH°f(HCl(g)) - 1 mol × ΔH°f(NaOH(s))

ΔH°r = 1 mol × (-411.15 kJ/mol) + 1 mol × (-285.83 kJ/mol) - 1 mol × (-92.31 kJ/mol) - 1 mol × (-425.61 kJ/mol)

ΔH°r = -179.06 kJ

7 0
3 years ago
When heated, lithium reacts with nitrogen to form lithium nitride: 6Li(s) + N2(g) → 2Li3N(s) What is the theoretical yield of Li
anyanavicka [17]

Answer:

The % yield of the reaction = 27.5 %

Explanation:

Step 1: Data given

Mass of Li = 12.7 grams

Mass of N2 = 34.7 grams

Actual yield of Li3N = 5.85 grams

Molar mass of  Lithium = 6.94 g/mol

Molar mass of N2 = 28 g/mol

Molar mass of LI3N = 34.83 g/mol

Step 2: The balanced equation:

6Li(s) + N2(g) → 2Li3N(s)

Step 3: Calculate moles of Lithium

Moles Li = mass Li / Molar mass Li

Moles Li = 12.7 grams / 6.94 g/mol

Moles Li = 1.83 moles

Step 4: Calculate moles of N2

Moles N2 = 34.7 g/ 28 g/mol

Moles N2 = 1.24 moles

Step 5: Limiting reactant

For 6 moles Li consumed, we need 1 mole of N2 to produce 2 moles of Li3N

Lithium is the limiting reactant. It will completely be consumed (1.83 moles).

N2 is in excess. There will be consumed 1.83 / 6 = 0.305 moles

There will remain 1.24 - 0.305 = 0.935 moles

Step 6: Calculate moles of Li3N

For 6 moles Li consumed, we need 1 mole of N2 to produce 2 moles of Li3N

For 1.83 moles Li, we'll have 1.83/3 = 0.61 moles of Li3N

Step 7: Calculate mass of Li3N

Mass Li3N =moles LI3N * Molar Mass LI3N

Mass Li3N = 0.610 moles * 34.83 g/mol

Mass Li3N = 21.2463 grams = Theoretical yield

Step 8: Calculate % yield

% yield = actual yield / theoretical yield

% yield = (5.85 / 21.2463)*100% = 27.5%

The % yield of the reaction = 27.5 %

8 0
3 years ago
Ethanol and water appear the saame to the naked eye at 25C. Which properties can help a chemist distinguish between? denisty, ma
Oxana [17]

Explanation:

As it is known that there are two types of properties. These are extensive and intensive.

Extensive properties : Properties that depend on the size or amount of system. For example, mass, volume etc.

Intensive properties : Properties that do not depend on the size or amount of system. For example, density, melting point, specific heat capacity etc.

On the basis of these properties water and ethanol are distinguished as follows.

  • Density of water is 997 kg/m^{3} whereas density of ethanol is 789 kg/m^{3}. Both these liquids can be separated by intensive properties.
  • Melting point of water is zero degree celsius whereas melting point of ethanol is -114.1 degree celsius.
  • Specific heat capacity of water is 4.184 J/g ^{o}C whereas specific heat capacity of ethanol is 2.46 J/g ^{o}C.
  • Mass of the given liquids cannot be differentiated because they will keep on changing depending on the quantity required. As mass is an extensive property, therefore, it is difficult to differentiate between the two liquids.

Thus, we can conclude that properties like density, melting point, specific heat capacity can help a chemist distinguish between ethanol and water.

7 0
3 years ago
Other questions:
  • A solution that contains a small amount of salt and a large amount of water is said to be a _______ solution.
    8·2 answers
  • Why is the thiosulfate solution stored in the dark?
    12·1 answer
  • In the process of photosynthesis, carbon dioxide and water react chemically, with the help of sunlight, to produce oxygen
    6·1 answer
  • 2.25 g/ml at 700mmHg, 200 C. Find molar mass of gas.
    15·1 answer
  • For which of the following molecules or ions does the following description apply? "The bonding can be explained using a set of
    12·2 answers
  • What is the theoretical yield of Li3N in grams when 12.7 g of Li is heated with 34.7 g of N2
    13·1 answer
  • Releases energy in the form of ATP
    15·1 answer
  • A precipitation reaction 2. A Lewis acid-base reaction the produces a coordination complex: A Lewis acid-base reaction the produ
    15·1 answer
  • 6. Which change to a population would cause
    9·1 answer
  • The reaction between calcium carbonate (CaCO3) and HCl produces calcium chloride (CaCl2), carbon dioxide (CO2), and water (H2O).
    6·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!