Answer:
This question is incomplete and unclear; the complete question including the missing part is:
Emelie is working on a science project. Her task is to answer the question:
"Does Rogooti (a hair cream sold on TV) affect the speed of hair growth
(in length)". Her family is willing to volunteer for the experiment. Identify the control group (CG) and the independent and dependent variables.
ANSWER:
Independent variable: Rogooti hair cream
Dependent variable: Speed of hair growth/length
Control group: Family members that do not use the Rogooti hair cream
Explanation:
In an experiment, the independent variable is the variable that the experimenter changes or manipulates in order to bring about a measurable response. In this case, the ROGOOTI HAIR CREAM is the independent variable.
Dependent variable refers to the variable that is measured or the variable that responds to the change made to the independent variable. In this case, the dependent variable is SPEED AT WHICH HAIR GROWS (IN LENGTH).
Control group in an experiment is the group that does not receive the experimental treatment. In this case, the experimental treatment is the Rogooti hair cream, hence, the control group will be the VOLUNTEER FAMILY MEMBERS THAT DOES NOT RECEIVE THE ROGOOTI HAIR CREAM ON THEIR HAIR.
Answer:
A
Explanation:
You can eliminate C because you need to consult a periodic table to determine the mass (not the weight).
There are other answers you could use. The wording is awfully sloppy. D is an example of that. The elements part is true, the atoms part is not really true in all cases. For example NaCl is table salt and both the elements are ions, not atoms. Na is plus ion and Cl is minus one. B is wrong for the same reason.
I think in the end I would choose A. I think this is a very sly question. It is not really testing chemistry. It is testing how well you know your definitions.
Mass=density x volume, i.e. 1.03 x 85.32 = 87.88 g
You're given Δh in terms of kJ/mol, so you need to convert mass of sulfur to moles of sulfur using its molar mass: 585 g / 32 g/mol = 18.28 mol.
Now you can find total heat using the given enthalpy of combustion:
<span>q = </span><span>Δh * n
</span>q = -296 kJ/mol * 18.28 mol
q = -5411 kJ
The negative indicates 5411 kJ of heat were released from the system.
Answer:
m = 3 moles/kg
Explanation:
This is a problem of freezing point depression, and the formula or expression to use is the following:
ΔT = i*Kf¨*m (1)
Where:
ΔT: Change of temperature of the solution
i: Van't Hoff factor
m: molality of solution
Kf: molal freezing point depression of water (Kf = 1.86 °C kg/mol)
Now, the value of i is the number of moles of particles obtained when 1 mol of a solute dissolves. In this case, we do not know what kind of solution is, so, we can assume this is a non electrolyte solute, and the value of i = 1.
Let's calculate the value m, which is the molality solving for (1):
m = ΔT/Kf (2)
Finally, let's calculate ΔT:
ΔT = T2 - T1
ΔT = 0 - (-5.58)
ΔT = 5.58 °C
Now, let's replace in (2):
m = 5.58/1.86
<em>m = 3 moles/kg</em>
<em>This is the molality of solution.</em>
<em>The other data of mass, can be used to calculate the molecular mass of this unknown solid, but it's not asked in the question.</em>