Answer: C) a general rule most people follow
The english phrase "rule of thumb" referes to an approximate method for doing something, based on practical experience rather than theory. An example of a rule of thumb would be: changing the oil of a car every certain number of milles traveled. "<em>To start with, change the oil every 5000 or 6000 miles". </em>In the example you can notice that is not strictly accurate or reliable for every situation.
The first one is a posituve
and the last 2 are negative
hope this help
Answer:
I believe the answer would be A and C
Step-by-step explanation:
Answer:
30% constituents=20 mL
10% constituents=180 mL
Step-by-step explanation:
x= 30% volume
y=10% volume
For our first equation, we know the total volume is 200 mL and is the sum
x+y=200
y=200-x (1)
For our second equation, we do a mass balance for 200 mL of final solution.
12% w/v = 0.12 g/mL
This means that in 1 mL of solution, we have 0.12 g of NaCl.
For any solution, concentration multiplied by volume will give the mass of NaCl:
Mass in x mL= C*V (g/mL) (mL)
So in 200 mL, we have
0.12*200 (g/mL) (mL)
=24g of NaCl
Cx*Vx + Cy*Vy=24
0.3x+0.1y=24 (2)
Substitute y=200-x into (2)
0.3x+0.1(200-x)=24
0.3x+20-0.1x=24
0.2x=24-20
0.2x=4
Divide both sides by 0.2
0.2x/0.2=4/0.2
x=20
Substitute x=20 into (1)
y=200-x
y=200-20
y=180
30% constituents=20 mL
10% constituents=180 mL
