Answer:
0.2 mol/dm³
Explanation:
Glucose = C₆H₁₂O₆
Mr = 180
1 mole of glucose is 180g
The ratio of the moles of glucose we have to the mass is going to be the same as the ratio of 1 mole to 180g;
In other words, we can formulate an equation and solve to find the number of moles we have (we'll let it be x):
ˣ/₇₂ = ¹/₁₈₀
x = ⁷²/₁₈₀
x = 0.4
The solution we have has 0.4 moles of glucose;
A key concept in calculating or finding a particular variable or quantity such as concentration is the units, they give major clues as to how to calculate said variable when you consider it logically;
Molarity (or equally, concentration) is the number or moles of a substance found in a given volume of solution;
The units are typically mol/dm³;
mol stands for moles and dm³ is a measure of volume (1 dm³ = 1 L);
If we therefore want to find the molarity, we need to divide moles by volume;
Recognising that 1 L = 1 dm³, we can see we have the moles of glucose, calculated above, and the volume of the solution (2 L or 2 dm³);
Then, to get the molarity (M), we simply calculate:
M = 0.4/2
M = 0.2
