Chemistry chapter 1: stoichoimetry Flashcards

1
Q

Define Avogadro’s number.

A

A: Avogadro’s number is
6.022×10^23, representing the number of atoms, molecules, ions or particles in one mole of a substance.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is a mole in chemistry?

A

A: A mole is the amount of substance that contains exactly
6.022×10^23
entities (atoms, molecules, ions, etc.), known as Avogadro’s number.

And it is the number of atomic, formula and molecular mass expressed in grams.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Why is chemistry considered a quantitative science, and how does it impact daily life?

A

A: Chemistry is considered a quantitative science because it involves measurements, calculations, and precise quantities (moles, mass, volume, etc.) used to predict outcomes. It impacts daily life in areas like medicine, food, environment, and industrial processes.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

How is the mole concept related to Avogadro’s number?

A

A: One mole of any substance contains

6.022×10^23 particles, such as atoms, molecules, or ions, which is Avogadro’s number.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

How do you calculate the number of atoms, molecules, moles, ions, protons, neutrons, or electrons?

A

A: Use the formula:
Number of particles=moles×Avogadro’s number

For protons, neutrons, and electrons, use atomic number and mass number to find the counts.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

How do you calculate interacting moles and representative particles from a balanced chemical equation?

A

A: Use the mole ratio from the balanced equation to convert between moles of reactants and products.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

How do you calculate the masses and volumes of gases at STP and RTP?

A

A: Use the molar volume of gas: 22.4 L at STP and 24 L at RTP. The formula is:
Volume=Moles×Molar volume.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How do you calculate the percentage by mass of elements in a compound?

A

A: Use the formula:

Percentage by mass= Mass of (element in 1 mole of compound/
Molar mass of compound)×100.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How do you solve stoichiometric problems using mole ratios?

A

A: Use the mole ratio from the balanced equation as a conversion factor to find the moles of reactants or products.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How do you calculate the percentage of water of crystallisation in hydrated salts?

A

A: Use the formula:

Percentage of water= (Mass of water/
Mass of hydrated salt)×100.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How do you deduce the empirical and molecular formula of a compound?

A

A: Find the simplest whole number ratio of atoms (empirical formula).
Use the molar mass and empirical formula to find the molecular formula:

Molecular formula= n(Empirical formula)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How do you determine the limiting reagent in a chemical reaction?

A

A: The limiting reagent is the reactant that is consumed first, limiting the amount of product formed. Compare the mole ratios of reactants to the balanced equation to determine this.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How do you calculate the maximum amount of product and the amount of excess reagent left unreacted?

A

A: Use the limiting reagent to calculate the moles of product.
Subtract the moles of excess reagent used from the initial moles to find the unreacted amount.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the difference between theoretical yield, actual yield, and percentage yield?

A

A:
- Theoretical yield is the maximum product calculated from the limiting reagent.
- Actual yield is the product obtained in practice.

  • Percentage yield= (Actual yield/Theoretical yield)×100.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How many molecules are present in 2 moles of water (H₂O)?

A

A:
Use Avogadro’s number:
1 mole=6.022×10^23 molecules.
Multiply by the number of moles:
2 moles of H₂O×6.022×10^23 =1.204×10^24 molecules.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Calculate the percentage of carbon in methane (CH₄).

A

Find the molar mass of CH₄:
12+(1×4)=16 g/mol

Use the formula for percentage composition:
Percentage of carbon

(12/16)×100=75%.

14
Q

In the reaction
2H2+O2→2H2O,
, if you have 3 moles of H₂ and 2 moles of O₂, what is the limiting reagent?

A

A:

  • According to the balanced equation, 2 moles of H₂ react with 1 mole of O₂.
  • For 3 moles of H₂, you would need
    3/2=1.5 moles of O₂
  • Since you have 2 moles of O₂ (more than required), H₂ is the limiting reagent.
15
Q

Define theoretical yield and actual yield in chemical reactions.

A

Theoretical yield is the maximum amount of product that can be produced from the limiting reagent, based on the stoichiometric calculations.
Actual yield is the amount of product actually obtained from a chemical reaction.

16
Q

How do mole ratios help in solving stoichiometry problems?

A

A: Mole ratios, derived from the coefficients of a balanced chemical equation, act as a conversion factor to relate the moles of reactants and products.

17
Q

What is the percentage of oxygen in water (H₂O)?
a) 11.11%
b) 88.89%
c) 33.33%
d) 50%

A

A: b) 88.89%

17
Q

What volume will 2 moles of oxygen gas occupy at STP?
a) 11.2 L
b) 22.4 L
c) 44.8 L
d) 24 L

A

A: c) 44.8 L
At STP, 1 mole of gas = 22.4 L, so 2 moles = 44.8 L

18
Q

How many moles are in
18.06 x 10^23 atoms of carbon?
a) 0.3 moles
b) 1.5 moles
c) 3 moles
d) 6 moles

A

A: c) 3 moles

19
Q

What is an empirical formula, and how is it different from a molecular formula?

A
  • Empirical formula is the simplest whole-number ratio of atoms in a compound.
  • Molecular formula shows the actual number of atoms of each element in a molecule.
20
Q

How is Avogadro’s number applied in chemical calculations?

A

: Avogadro’s number is used to convert between moles and the number of atoms, molecules, or ions in a substance, aiding in quantitative chemical analysis.

20
Q

in reaction
N2 + 3H2 –> 2NH3
, if 1 mole of nitrogen reacts with 3 moles of hydrogen, what is the limiting reagent?
a) Nitrogen
b) Hydrogen
c) Ammonia
d) None

A

A: d) None
The reactants are present in the exact stoichiometric ratio, so neither is limiting.

21
Q

in reaction:
2H2 + O2 —> 2H2O, how many moles of water are produced when 4 moles of hydrogen react?

A

According to the balanced equation, 2 moles of H₂ produce 2 moles of H₂O.
Therefore, 4 moles of H₂ will produce 4 moles of H₂O.

22
Q

Calculate the volume of 10 g of oxygen gas (O₂) at STP.

A
  • Find the molar mass of O₂:
    32 g/mol.
  • Calculate the moles: 10/32
    =0.3125 moles.
  • Use the molar volume at STP:
    Volume=0.3125×22.4=7 L.
23
Q

chemistry?

A

branch of science that deals with the study of properties, structure, composition and the changes that occur in matter along with the laws that govern these changes.

24
Q

compounds

A

a substance formed by the chemical bonding of elements

25
Q

elements

A

a substance made up of one type of atoms having the same proton number

26
Q

ion

A

charged atom.
- cation: positively charged
- anion: negatively charged

27
Q

Stoichiometry

A

Branch of chemistry that deals with the QUANTITATIVE measures of the relationship between the reactants and the products in a balanced chemical equation.