Chemistry Moles Flashcards

1
Q

How many atoms are there in one mole of O atom

A

6.02 ✖10^23 atoms

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2
Q
From the solution in each tube , the student obtained crystals with the formula MgCl2⃣.6H2⃣O
Calculate the relative formula
Mg=24.3
Cl = 35.5
H = 1
O = 16
A

203.3 g mol ^-1

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3
Q

Calculate the number if moles in a solid

A

Moles = mass of substance ➗ molar mass

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4
Q

A Bronze Age shield found on Dartmoor contained 2.08 kg of tin.
Calculate the number of tin atoms in the shield.

A

2.08 ✖1000 = 2080

2080 ➗ 118.7 = 17.5 mol

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5
Q

Calculating number of moles in a liquid

A

Moles = (concentration ✖ volume) ➗ 1000

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6
Q

What volume of 0.1 M of sulphuric acid contains 0.002 moles?

A

(1000 ✖ 0.002) ➗ 0.1 = 20 cm^3

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7
Q

Calculating moles when given a gas

A

Moles = volume ➗ 24(000)

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8
Q

Analysis of a compound shows that it contained 74.19% of Na and 25.81% of O. What is the empirical formula of this compound?

A

Na

  1. 19 ➗ 23 = 3.23
  2. 23 ➗ 1.61 = 2

O

  1. 81 ➗ 16 = 1.61
  2. 61 ➗ 1.61 = 1

Na2⃣O

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9
Q

Calculate the molecular formula of a compound of empirical formula CH2⃣ and relative molecular mass of 84

A

Mass of CH2⃣ = 14
84 ➗ 14 = 6
C6⃣H1⃣2⃣

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10
Q

Sodium ➕ water ——> sodium hydroxide ➕ hydrogen

Balance symbol equation with state symbols

A

2Na (s) ➕ 2H2⃣O (l) —–> 2NaOH (aq) ➕ H2⃣ (g)

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11
Q

Calculate the volume of 0.1 M of hydrochloric acid which neutralise 23.55 cm^3 of 0.12 M of sodium hydroxide

A

HCl ➕ NaOH —–> NaCl ➕ H2⃣O
n of NaOH = 0.12 ➗ 23.5 = 0.002826 mol
N of HCl = 0.002826 mol
V = (0.002826 ✖ 1000) ➗ 0.1 = 28.26 cm^3

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12
Q

Sodium nitrate decomposes on heating as follows
2NaNO3⃣ —–> 2NaNO2⃣ ➕ O2⃣
What volume of oxygen is produced when 6.8 g sodium nitrate is heated?

A

n of NaNO3⃣= 6.8 ➗ 69 = 0.09855 mol
n of O2⃣ = 0.09855 ➗ 2 = 0.04928 mol
V of O2⃣ = 0.04928 ✖ 24 = 1.18 dm^3

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