Question

Question #ac840

Answer 1

`"m"` `= 1.98` `"kg"`

Explanation:

Yes you can.

The formula for density is `rho = frac("m")("V")`; where `rho` is the density, `"m"` is the mass, and `"V"` is the volume.

Let's substitute the relevant values into the equation:

`Rightarrow 0.793` `"kg L"^(- 1) = frac("m")(2.5 " L")`

`Rightarrow 0.793` `"kg L"^(- 1) times 2.5` `"L" = frac("m")(2.5 " L") times 2.5` `"L"`

`Rightarrow 1.9825` `"kg"` `=` `"m"`

`therefore` `"m" = 1.98` `"kg"`

Therefore, the mass of solute is `1.98` `"kg"`.

Answer 2

The mass of solute is `"2.0 kg"`.

Refer to the explanation for the process.

Explanation:

Another way of expressing the density formula is:

`D=M/V`, where D is density, M is mass, and V is volume.

(It doesn't hurt to know that the Greek lowercase letter rho, `rho`, is a symbol for density. The Latin D is also acceptable.)

The question gives volume and density, and asks for the mass, which is unknown.

Solution

Rearrange the density formula to isolate `M`. Plug in the known values and solve.

`M=DxxV`

`M="0.793 kg"/color(red)cancel(color(black)("L"))xx2.5color(red)cancel(color(black)("L"))="2.0 kg"` (rounded to two significant figures due to 2.5 L)