A student had calculated the theoretical yield of a product was 8 g. The actual yield obtained was 6 g. What was the percentage yield?
48%
75%
133%
Which equation shows a substance dissolved in water reacting to form a gas?
Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g)
C(s) + H2O(g) → CO(g) + H2(g)
HCl(g) + NaOH(aq) → NaCl(aq) + H2O(l)
In this unbalanced symbol equation: Na + Cl2 → NaCl what is the correct balanced equation?
2Na + Cl2 → NaCl
2Na + Cl2 → 2NaCl
Na + Cl2 → 2NaCl
What is meant by the relative atomic mass of an element (also represented as the symbol Ar)?
It is the mass of an atom of a particular element measured in grams
It is the actual mass of an atom of an element compared to the mass of a molecule of the element
It is the average mass of the atoms of an element compared to the mass of an atom of carbon-12
What is the relative atomic mass (Ar) of aluminium? Use the periodic table to help you.
13
14
27
What is the relative formula mass (Mr) of magnesium oxide (formula MgO)? Use the periodic table to help you.
40
30
20
What is the relative formula mass (Mr) for sulfuric acid (formula H2SO4)? Use the periodic table to help you.
50
98
49
What does the law of conservation of mass state?
That the total mass of the reactants will always be the same as the total mass of the products
That the total mass of the reactants will always be more than the total mass of the products
That the total mass of the reactants will always be less than the total mass of the products
What mass of cobalt must have reacted if 3.20 g of oxygen forms 7.92 g of cobalt oxide?
3.20 g
4.72 g
7.92 g
Osmium tetroxide (OsO4) is an important chemical in the synthesis of molecules which can be used in a variety of medicines. What is the percentage of osmium tetroxide that is made up of oxygen?
Ar of oxygen, O = 16, Ar of osmium, Os = 190.
7.8 %
25.2 %
74.8 %