MCQ Chemistry

@Pigster

It's written why option A is not correct .

But I didn't understand what it means

DH = -Q/n
DH is constant.
n(water) is x2 (since there is twice as much acid)
Therefore Q is x2

Q = mcDT
Q is x2 (from above)
c is constant
m is x4/3
2T = 4/3m x c x DT
DT is...
(a little algebra later)
B

I didn't get it

Which bit?

The whole thing in general. Especially the m ?

m = mass of thing that you stick your thermometer into.

In the first expt, m = 30 g (10 cm3 + 20 cm3)
In the second, m = 40 g, i.e. 40/30x heavier.

This entire calculation process seems quite complicated for me.

Like, I need the values for each quantity, but what should I do with ×2 or × 4/3 ?

I'm so confused about the entire thing.

There is twice as much acid, so twice as much energy is released. Happy so far?

If that energy went into the same volume (and hence mass) of mixture, DT would be twice as much.

But the energy is going into a larger mass, so DT won't be as big.

The larger mass is in fact 4/3x larger, so produces 3/4x of the expected increase.

3/4 of 2 is 1.5.