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2 years ago

Calculate the number of cells in a hummingbird assuming it weighs 10-2 kg

1 answer:

5 0

A popular assumption is that the mass of a cell s 10 times the mass of a bacterium, which is about 10⁻¹² g.
Therefore, one cell of the humming bird has a mass of about 10⁻¹¹ g.

The number of cells in a hummingbird weighing 10⁻² g is
10⁻²/10⁻¹¹ = 10⁹

Answer: 10⁹ or a billion.

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Anyway, which is a spectator ion involved in the reaction of k2cro4(aq) and ba(no3)2(aq)?

marissa [1.9K]

Nitrate ions $\text{NO}_3^{-}$ and potassium ions $\text{K}^{+}$ .

<h3>Explanation</h3>

Potassium dichromate undergoes a double-decomposition reaction with barium nitrate to produce barium dichromate and potassium nitrate. The reaction is possible due to the low solubility of barium dichromate that precipitate out of the solution readily after its production.

Start with the balanced chemical equation for this process:

$\text{K}_2\text{CrO}_4 \; (aq) + \text{Ba}(\text{NO}_3)_2 \; (aq) \to \text{Ba}(\text{CrO}_4)_2 \; (s) + 2 \; \text{KNO}_3 \; (aq)$

Rewrite the chemical equation as an ionic one; express all soluble salts- those with state symbol (aq)- as their constituting ions while leaving the insoluble (s) intact.

$2 \; \text{K}^{+}\; (aq)+ 2\; \text{CrO}_4^{-} \; (aq) + \text{Ba}^{2+} \; (aq) + 2 \; \text{NO}_3^{-} \; (aq) \\ \to \text{Ba}(\text{CrO}_4)_2 \; (s) + 2 \; \text{K}^{+} \; (aq) + 2 \; \text{NO}_3^{-} \; (aq)$

$\text{K}^{+}$ and $\text{CrO}_4^{-}$ are found on both sides of the equation by the same quantity. The two ions thus took no part in the net reaction and act as spectator ions.

5 0

2 years ago

What is the density of a piece of metal in g/cm3 if its mass is determined to be 42.20 g and it is in the shape of a cube, with

maria [59]

It's a cube so the volume = edge^3
Volume = 2.5^3 cm^3 = 15.625 cm^3

density = mass / volume = 42.20 / 15.625 = 2.70 You have 3 places of accuracy.

density of object = 2.70 grams / cm^3 <<<<=== answer.

4 0

2 years ago

Read 2 more answers

The rate of disappearance of HBr in the gas phase reaction 2 HBr(g) → H2(g) + Br2(g) is 0.140 M s-1 at 150°C. The rate of appear

djverab [1.8K]

Answer: The rate of appearance of $Br_2$ is $0.0700Ms^{-1}$

Explanation:

Rate law says that rate of a reaction is directly proportional to the concentration of the reactants each raised to a stoichiometric coefficient determined experimentally called as order.

$2HBr(g)\rightarrow H_2(g)+Br(g)$

The rate in terms of reactants is given as negative as the concentration of reactants is decreasing with time whereas the rate in terms of products is given as positive as the concentration of products is increasing with time.

Rate in terms of disappearance of HBr = $-\frac{1d[HBr]}{2dt}Rate in terms of appearance of [tex]H_2$ = $\frac{1d[H_2]}{dt}$

Rate in terms of appearance of $Br_2$ = $\frac{1d[Br_2]}{dt}$

$-\frac{1d[HBr]}{2dt}=\frac{d[H_2]}{dt}=\frac{d[Br_2]}{dt}$

Given :

$-\frac{1d[HBr]}{dt}=0.140Ms^{-1}$

The rate of appearance of $Br_2$ ;

$\frac{1d[Br_2]}{dt}=-\frac{1d[HBr]}{2dt}=\frac{1}{2}\times 0.140=0.0700Ms^{-1}$

Thus rate of appearance of $Br_2$ is $0.0700Ms^{-1}$

6 0

2 years ago

A NiCd battery uses nickel and cadmium to produce a potential difference. Using these equations, answer the following questions.

Dahasolnce [82]

Answer : The correct chemical reaction within the galvanic cell is,

(3) $Cd(s)+2NiO(OH)(s)+2H_2O(l)\rightarrow 2Ni(OH)_2(s)+Cd(OH)_2(s)$

Explanation :

Galvanic cell : It is defined as a device which is used for the conversion of the chemical energy produces in a redox reaction into the electrical energy. It is also known as the electrochemical cell.

The redox reaction occurs between the nickel and cadmium.

In the galvanic cell, the oxidation occurs at an anode which is a negative electrode and the reduction occurs at the cathode which is a positive electrode.

The balanced two-half reactions will be,

Oxidation half reaction : $Cd(s)+2OH^-(aq)\rightarrow Cd(OH)_2(aq)+2e^-$

Reduction half reaction : $NiO(OH)(aq)+H_2O(l)+e^-\rightarrow Ni(OH)_2(aq)+OH^-(aq)$

Thus the overall reaction will be,

$Cd(s)+2NiO(OH)(s)+2H_2O(l)\rightarrow 2Ni(OH)_2(s)+Cd(OH)_2(s)$

6 0

2 years ago

Yesinia read that certain perfume ingredients, called esters, would agitate bees. Because perfume formulas are secret, she decid

RUDIKE [14]

Answer:

Hypothesis: IF the perfumes contained Ester "X", THEN the bees would be agitated

Control group: The control group would be the group of bees that did not receive any perfume treatment

Experimental group: Bees that were exposed to the different perfumes

Independent variable: The type of perfumes

Dependent variable: the behavior of the bees

Explanation:

An hypothesis is a testable explanation or suggested solution to a problem that is subject to testing (for proving or disproving) via experimentation. The hypothesis of this experiment will be: IF the perfumes contained Ester "X", THEN the bees would be agitated

The control group of an experiment is the group that does not receive the experimental treatment or the group whose independent variable is not changed. In this case, there is no stated control group but control group of this particular experiment could be the BEES THAT WERE NOT EXPOSED TO ANY PERFUME.

The experimental group, as opposed to the control group, is the group that receives experimental treatment. In this case, it is the group of bees that were exposed to the different types of perfumes.

In an experiment, the variable that is deliberately changed by the experimenter is called the independent variable. The independent variable in this question is the TYPE OF PERFUME given to the bees.

The variable that responds to the changes made to the independent variable is called the dependent variable. The dependent variable, which is the measured variable, is THE BEHAVIOR OF THE BEES.

6 0

2 years ago