Calculation In Chemistry IGCSE Quiz!

Explanation
The correct answer is Fe(OH)3 because Iron III hydroxide is a compound formed by the combination of one iron atom (Fe) and three hydroxide ions (OH-). The subscript 3 indicates that there are three hydroxide ions present for every one iron atom in the compound.

Explanation
The relative formula mass of Calcium hydroxide (Ca(OH)2) can be calculated by adding the atomic masses of each element in the formula. The atomic mass of calcium (Ca) is 40 amu, the atomic mass of oxygen (O) is 16 amu, and the atomic mass of hydrogen (H) is 1 amu. Since there are two hydroxide groups in the formula, we multiply the atomic mass of hydroxide (OH) by 2, which is (16 + 1) x 2 = 34 amu. Adding the atomic masses together, we get 40 + 34 = 74 amu as the relative formula mass of Calcium hydroxide.

Explanation
The molar mass of carbon dioxide (CO2) is calculated by adding the atomic masses of carbon (12.01 g/mol) and oxygen (16.00 g/mol) together. This gives a total molar mass of 44.01 g/mol. Since the question asks for the mass of 2 moles of carbon dioxide, we simply multiply the molar mass by 2, resulting in a mass of 88 g.

Explanation
The molar mass of H2SO4 is 98 g/mol. To find the number of moles, divide the given mass (9.8 g) by the molar mass. 9.8 g / 98 g/mol = 0.1 mol. Therefore, there are 0.1 moles of sulphuric acid in 9.8g.

Explanation
Avogadro's number is the correct answer because it represents the number of atoms found in one mole of any substance, not just silver atoms. It is a fundamental constant in chemistry and is approximately equal to 6.022 x 10^23. This number allows scientists to relate the mass of a substance to the number of atoms or molecules it contains, making it an essential concept in stoichiometry and other calculations involving the mole.

Explanation
When balancing the equation, we need to ensure that the number of atoms on both sides of the equation is equal. In this case, there are 2 hydrogen atoms on the left side and 2 hydrogen atoms on the right side. Similarly, there are 2 oxygen atoms on the left side and 1 oxygen atom on the right side. To balance the equation, we need to multiply the coefficients of H2 and O2 by 2, resulting in 2H2 + O2 -> 2H2O. Therefore, the sum of all coefficients is 2 + 1 + 2 = 5.

Explanation
The correct answer is 1 - 3 - 2. This is because in the balanced chemical equation, there needs to be an equal number of atoms on both sides of the equation. In this case, there are 2 nitrogen atoms on the left side (N2) and 2 nitrogen atoms on the right side (NH3). Therefore, the coefficient for N2 is 1. There are 6 hydrogen atoms on the left side (3H2) and 6 hydrogen atoms on the right side (2NH3). Therefore, the coefficient for H2 is 3. Finally, there are 2 ammonia molecules on the right side (NH3). Therefore, the coefficient for NH3 is 2.

Explanation
The molar mass of C6H12O6 is approximately 180 g/mol. Therefore, to find the mass of 5 moles of C6H12O6, we can multiply the molar mass by the number of moles: 180 g/mol * 5 moles = 900 g.