Question

which of the folowing has lowest weight?

1) 6.023 x 1022 molecules of glucose

2) 18ml of water at 40C

3) 11200ml of CH4 at stp

4) 5.6 litre of CO2 at stp

Answer 1

Weight of 6.022 x 10²² glucose(C6H12O6 ) molecules = 1 mole of glucose = molar mass = 12 x6 + 1 x12+ 16 x 6= 180gm

At, 4°C, density of water = 1gm/ml

so, weight, of 18 ml of water = 18 gm

At,STP, 22400 ml = 1 mole methane(CH4 ) = 16gm

so, 11400 ml of CH4 = 8 gm

Similarly, at STP, 22.4 L of CO2 = 1 mole = 40 gm

So, 5.6 L of CO2 = (40/22.4 )x 5.6 = 10 gm

Here, we see that, the lowest weight is for 11400 ml of methane CH4 = 8gm

Hence, answer is 3.

Answer 2

Answer:

3)11200ml of CH4 at STP has the lowest weight

Explanation:

Weights of the given compounds at different conditions is calculated as follows

1)

$\\ 6.023 \times 10 {}^{22} \: molecules \: of \: glucose$

It means 1 mole of glucose.We know that 1 mole of glucose has weight

$C_{6}H_{12}O_{6} \\ = 6 \times 12 + 12 \times 1 + 6 \times 16 \\ = 72 + 12 + 96 = 180 \: gm$

Therefore its weight is 180gm

2)18 ml of water at 40°C

The density of water at 40°C is less than the density of water at 0°C.Hence the weight of water at 40°C will be less than that of 0°C.

Weight of 18ml water at 0°C=18gm

=>Weight at 40°C is <18gm

3)11200ml of CH4 at STP

We know that at STP,1 mole of any gas occupies 22.4L or 22400ml

Therefore,weight of 11200ml of CH4 at STP is

$\frac{11200}{22400} \times 16 = 8gm$

4)5.6L of CO2 at STP

We know that at STP,1 mole of any gas occupies 22.4L

Therefore,weight of 5.6L of CO2 at STP is

$\frac{5.6}{22.4} \times 44 = 11gm$

Hence,out of all of these 3)11200ml of CH4 at STP has the least weight

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