3. (a) Which of the following is the formula of a cation?
Put a cross (✗) in the box next to your answer - Edexcel - GCSE Chemistry - Question 3 - 2015 - Paper 1
Question 3
3.
(a) Which of the following is the formula of a cation?
Put a cross (✗) in the box next to your answer.
A Mg
B Na⁺
C H₂O
D F⁻
(b) (i) The formul... show full transcript
Worked Solution & Example Answer:3. (a) Which of the following is the formula of a cation?
Put a cross (✗) in the box next to your answer - Edexcel - GCSE Chemistry - Question 3 - 2015 - Paper 1
Step 1
Which of the following is the formula of a cation?
96%
114 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
The correct answer is C: Na⁺. Cations are positively charged ions, and among the options provided, Na⁺ is the only one.
Step 2
The formula of a potassium ion is K⁺ and of a carbonate ion is CO₃²⁻:
99%
104 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
A potassium ion has a charge of +1, represented as K⁺. A carbonate ion has a charge of -2, represented as CO₃²⁻.
Step 3
Describe how you would obtain a pure, dry sample of barium sulfate from the mixture in the beaker.
96%
101 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
First, filter the mixture using filter paper and a funnel to separate the solid barium sulfate from the liquid. Ensure to wash the solid with distilled water to remove impurities. Then, allow the barium sulfate to dry completely.
Step 4
Describe, in terms of electrons, how a magnesium atom and an oxygen atom form ions in magnesium oxide, MgO.
98%
120 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
A magnesium atom has two electrons in its outer shell (2.8.2) and tends to lose these two electrons to achieve a stable electron configuration, forming a Mg²⁺ ion. An oxygen atom, having six electrons in its outer shell (2.6), gains two electrons to complete its octet, forming an O²⁻ ion. Thus, MgO consists of Mg²⁺ and O²⁻ ions held together by ionic bonds.
Step 5
Calculate the relative formula mass of magnesium oxide, MgO.
97%
117 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
The relative formula mass of magnesium oxide (MgO) can be calculated by adding the atomic masses of magnesium and oxygen. Given, Mg = 24 and O = 16:
