<em>ANSWER</em>
The number of moles of methane is 905.32 moles
STEP-BY-STEP EXPLANATION:
Given information
The number of particles of methane = 5.45 x 10^26 particles
Let x represents the number of moles of methane
To calculate the number of moles, we will be using the below formula

Recall that, the Avogadro's constant is given as


Therefore, the number of moles of methane is 905.32 moles
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The mass of NiCl₂•6HO₂ needed to prepare a 0.035 M 500 mL solution of NiCl₂•6HO₂ is 4.165 g
<h3>What is molarity? </h3>
This is defined as the mole of solute per unit litre of solution. Mathematically, it can be expressed as:
Molarity = mole / Volume
<h3>How to determine the mole of NiCl₂•6HO₂</h3>
- Molarity = 0.035 M
- Volume = 500 mL = 500 / 1000 = 0.5 L
Mole = Molarity × Volume
Mole of NiCl₂•6HO₂ = 0.035 × 0.5
Mole of NiCl₂•6HO₂ = 0.0175 mole
<h3>How to determine the mass of NiCl₂•6HO₂</h3>
- Mole of NiCl₂•6HO₂ = 0.0175 mole
- Molar mass of NiCl₂•6HO₂ = 238 g/mol
Mass = mole × molar mass
Mass of NiCl₂•6HO₂ = 0.0175 × 238
Mass of NiCl₂•6HO₂ = 4.165 g
Thus, 4.165 g of NiCl₂•6HO₂ is needed to prepare the solution
Learn more about molarity:
brainly.com/question/15370276
Answer: -
100 grams
Explanation: -
Mass of Oxygen = 40 g
Chemical formula of oxygen gas = O2
Molar mass of oxygen = 16 x 2 = 32 gram
Atomic mass of Mg = 24g
Molar mass of MgO = 24 x 1 + 16 x 1 =40 gram
The balanced chemical equation for the reaction is
2Mg + O2 -- > 2 MgO
So from the balanced equation we see that 1 O2 react to give 2 MgO
32 grams of O2 react to give 2 x 40 gram of MgO
40 grams of O2 react to give 
=100 gram of MgO