To prepare 1.00 l 1.00 mol / L NaCl solution, 58,5 g NaCl can be dissolved in 1.00 L water, right,

To prepare 1.00 l 1.00 mol / L NaCl solution, 58,5 g NaCl can be dissolved in 1.00 L water, right,

1 L is the volume of solution, 1.00 mol / L is the concentration of substance, the concentration of solute substance = the concentration of solute substance / the volume of solution; the concentration of solute substance = the concentration of solute substance multiplied by the volume of solution; according to the known conditions, the concentration of solute substance is 1.00 mol / L multiplied by 1 L = 1 mol

What is disjunctive calculation

In the calculation of mixed operation, it is usually to calculate a formula one step at a time (step-by-step calculation, the equal sign can not be written on the original formula), and the process of each step should be written. Generally speaking, the equal sign should be forward, not aligned with the first line, that is, it is to leave the original formula calculation

When the lamp L works normally, the current is 0.3A, the filament resistance is 20 ohm, but the power supply voltage is 8V, how much resistance should be connected in series to the lamp?

If the power supply voltage is 8V and the current limit is 0.3A, then r = u / I = 8 / 0.3 = 80 / 3 (Ω)
Because r total = R Lamp + R string, R string = R total - R lamp = 80 / 3-20 = 20 / 3 Ω ≈ 6.67 Ω
A: slightly

(), 35,63,80,99143 series

35 = 36-1 = 6 * 6-1 63 = 64-1 = 8 * 8-1 80 = 81-1 = 9 * 9-1 99 = 100-1 = 10 * 10-1 143 = 144-1 = 12 * 12-1 prime number: 2,3,5,7,11,13,... Combined number: 4,6,8,9,10,12,14,... Combined number distribution order by 6,8,9,10,12

Calculation of pressure
An elevator apartment building is about 40 meters high. To complete the building, it needs to cast 1 * 10 ^ 4 cubic meters of reinforced concrete and 305 * 10 ^ 4 tons of other building materials. The concrete area is 2.5 * 10 ^ 3 kg / m3, g = 10 N / kg
(1) The density of tap water is always 1 * 10 ^ 3kg / m3. In order to provide tap water from the ground to the top of the building, how much pressure does the pressure equipment need at least?
(2) The measurement shows that the pressure on the foundation of the building shall not exceed 102 * 10 ^ 6 Pa. if the contact area between the foundation and the ground is 1 * 10 ^ 3 square meters, what is the total mass of additional decoration materials, various equipment and other materials and personnel entering the building?
I'll score

1. Just use the water pressure formula, P = pGH = 1 * 10 ＾ 3 * 10 ＾ 40 = 4 * 10 ＾ 5pa
2. We can set the total mass of all kinds of equipment and other materials and personnel entering the building as G, then there is the following relationship
1 * 10 ＾ 4 * 2.5 * 10 ＾ 3 + 305 * 10 ＾ 4 + G ＜ = 102 * 10 ＾ 6 * 1 * 10 ＾ 3
G＜＝11．0197195＊10＾11

It is known that the hyperbola x squared - 3 / y passes through P (2,1) to make a straight line intersection, and the hyperbola AB makes P
Given that hyperbola x ^ - y ^ / 3 = 1, through P (2,1) make straight line intersection, hyperbola AB two points make
Finding the length of string ab

A (x1, Y1) B (X2, Y2) then X1 + x2 = 4, Y1 + y2 = 2, and because a and B are on hyperbola X1 ^ 2-y1 ^ 1 / 3 = 1x2 ^ 2-y2 ^ 2 / 3 = 1, subtracting the two formulas to get (x1 + x2) (x1-x2) - (Y1 + Y2) (y1-y2) / 3 = 0, substituting X1 + x2 = 4, Y1 + y2 = 2 to get y1-y2 / x1-x2 = 6, that is, the slope is 6

What kind of resistance do three LED need to use 220 V power supply? Three LED in series is 9 V withstand voltage. If I use 220 V power supply, what type of resistance do I need?

If the power consumption of LED is too large, even if 10mA is used, the resistance needs 22K, 3W or more power, and any type of resistance can be used. If the power of LED is larger, the power consumption will be even greater. It is better to use capacitor, no power consumption. Calculate the capacitor with formula 1 / 2 π FC, and the capacitor withstand voltage is above 400V

Let f (x) = x & # 178; a 2x + 3 prove that f (x) is an increasing function on (1,10 ∞)

F (x) = x & # 178; one 2x ten 3
=﹙x-1﹚²+2
The axis of symmetry x = 1, opening upward
(1,10 ∞) is an increasing function

A family has five rooms. If each room has a 36 watt energy-saving lamp, how many kilowatts of electricity will the family consume from 6 p.m. to 6 a.m. the next day

Theoretically, the daily power consumption is 5 * 36 * 12 / 1000 = 2.16 (KWH)

Y = LN2 y '=? Y = 1 / X to the second power y' =? Y = 2 to the x power y '=? Y = log2 x y' =?

y'=0
y'=-2/x^3
y'2^x *ln2
y'=1/(xln2)