The answer is 0.5010
Number of moles (n) is equal to the quotient of mass (m) and molar mass of a sample (Mr):
n = m/Mr
We have:
n = ?
m = 40.10 g
Mr = 80.0432 g/mol
n = 40.10 g : 80.0432 g/mol = 0.5010
<span>40.10 has 4 significant digits,
</span><span>80.0432 has 6 significant digits.
Since 4 is less than 6, we choose 4 </span>significant digits
1. Molarity : 0.25 M
2. mol CH₄ = 7.4 moles
mol O₂ = 14.8 moles
<h3>Further explanation</h3>
1.
Given
83.2 g CuCl2 in 2.5 liters of water
Required
the molarity
Solution
Molarity : mol solute per liter of solution(not per liter of solvent)
mol solute = mol CuCl₂
mol CuCl₂ = mass : MW CuCl₂
mol CuCl₂ = 83.2 : 134.45
mol CuCl₂ = 0.619
Molarity(M) = mol : V
Assume density CuCl₂ = 3.39 g/cm³
volume CuCl₂ = 8.32 g : 3.39 g/cm³ = 2.45 cm³=2.45 x 10⁻³ L
With this small volume value of CuCl₂, the volume of the solute is sometimes neglected in calculating molarity
volume of solution = 2.5 L + 2.45 x 10⁻³ L = 2.50245 L
Molarity(M) = mol : V
M = 0.619 : 2.50245 L = 0.247≈0.25
2.
Given
Reaction
The correct balanced reaction:
CH4 + 2O2 → CO2 + 2H2O
7.4 moles CO2
Required
moles of methane (CH4) and oxygen gas (O2)
Solution
From the equation, mol ratio of CO₂ : CH₄ : O₂ = 1 : 1 : 2
mol CH₄ = mol CO₂ = 7.4 moles
mol O₂ = 2 x mol CO₂ = 2 x 7.4 moles = 14.8 moles
Answer: Radon-222 is generated in the uranium series from the alpha decay of radium-226, which has a half-life of 1600 years. Radon-222 itself alpha decays to polonium-218 with a half-life of approximately 3.82 days, making it the most stable isotope of radon. Its final decay product is stable lead-20
The answer is 67.82 g/mol
Answer:
Mass of Ca(OH)₂ required = 0.09 g
Explanation:
Given data:
Volume of HNO₃ = 25 mL (25/1000 = 0.025 L)
Molarity of HNO₃ = 0.100 M
Mass of Ca(OH)₂ required = ?
Solution:
Chemical equation;
Ca(OH)₂ + 2HNO₃ → Ca(NO)₃ + 2H₂O
Number of moles of HNO₃:
Molarity = number of moles / volume in L
0.100 M = number of moles / 0.025 L
Number of moles = 0.100 M ×0.025 L
Number of moles = 0.0025 mol
Now we will compare the moles of Ca(OH)₂ with HNO₃ from balance chemical equation.
HNO₃ : Ca(OH)₂
2 : 1
0.0025 : 1/2×0.0025 = 0.00125
Mass of Ca(OH)₂:
Mass = number of moles × molar mass
Mass = 0.00125 mol × 74.1 g/mol
Mass = 0.09 g